Jon Risch distortion test signal [Archive]

Resident Loser

08-30-2004, 06:13 AM

...we do think we are sooo clever...I don't suppose it ever crossed your mind that most folks couldn't really give a r@t$-@$$ re: the writings of Chairman Jon...I know in my case at least, this place doesn't even exist on weekends, and I rarely get involved in long, laborious posts on Fridays...

But since you asked in an oh, so confrontationally condecsending tone, here goes...

Now perhaps my take on the "article" is flawed, but I don't fancy myself as anything othere than what I am, the thinking sheep...my reading comprehension is okee-dokee and I approach certain things more on an intuitive "gut-level" than any real "techy" one...although it plays a part along with a heapin' helpin' of common sense...with that in mind, here is my opinion...

Staticians can take numbers to prove just about anything so, it is equally plausible that a test, or tone or just about anything can be contrived to also "prove" a point...Not to infer any attempt a blatant deception, but one can easily claim to have "discovered" or "uncovered" something that may, in practical application, be absolutely nothing...

Music(as most musicians know) is a series of mathematical relationships...so when it is mentioned that this "new" test is not comprised of "multiples" of what practical application is it?...Notes in a specific key are in some sense "mutiples", most certainly octaves are, and what about the overtones that help identify the source instrument? Is this tone played as though it were a "chord"?...is it a series of arpeggiated tones, which would simply make it the oft-discounted "test tones"...perhaps this test only has bearing if one listens to the Throat Singers of Tuva, forms of dissonant music, Shoenberg, Ives...perhaps 12 tone or microtonal pieces...

Perhaps, the "squeaky clean" recorder isn't...What protcols were followed to be quite certain the source material itself isn't contaminated in some way? Flaw in Step One?...Additionally, if you have a result in mind, it is quite possible to unconsciously skew any procedure...

And then of course there is, what I consider "editorializing" in a what is ostensibly a "tech" article, "so much for all CDPs sound alike"...Who ever said that? It has been said transports read ones and zeros...that error correction and such is fairly identical...after all I think it's SONY and Philips who arrived at the standard and who produce the vast bulk of the transports used...the output is then "tweaked" to provide the specific "sonic signature" each manufacturer thinks they can sell...There is some high-priced unit that was touted around these parts not too long ago...uses a Philips transport and has an output section capable of providing "signal shaping" or some other audiophile-grade euphimism for tone controls...

Then of course there is mention of the contingent who will refuse to believe his results...apparently, there are those above and beyond our little peanut-gallery here, who have much greater knowledge and experience in the field(and with the author) who will be responsible for whatever scrutiny might need to be applied...

As was admitted in the article, the author doesn't even seem to have any real conclusions, only the hope that his work might be the basis for further investigation...

I wish him all the luck and will let those best suited for the job have at it...

Anything provided here is just so much idle chatter, more hits for E-centives and not much more...as markw noted, let the AES do what they must...

jimHJJ(...be careful what you ask for...)

Monstrous Mike

08-30-2004, 09:48 AM

I'm just shocked :eek: that no naysayers are willing to think for themselves and venture any thoughts about the technical merits of Risch's idea. The simple possibility that Risch's approach might prove to provide another measurement aspect that could help to quantify the sound of a component is reason enough to be excited about it. But, drawing that conclusion relies on independent thinking instead of on edicts from external authorities, so maybe I shouldn't be surprised about the lack of response.
The information contained on those web pages of Jon Risch is not extensive enough to draw any conclusions. I sincerely hope he does come up with a measurement method that more closely analyzes what is going on in a cable.

And like all yeasayers decree, the proof is in the listening. Therefore, when a test shows conclusively that an audio cable is causing distortion, then it will be necessary to determine if that distortion is audible. And that means a controlled listening test.

I can't speak for everybody, but the results of a listening test with correlation to cable distortion is the first point in time I would spend any effort in a detailed analysis. And then the big step would be to determine which cables can reduce audible distortion. That is really what we are interested in, is it not?

markw

08-30-2004, 02:15 PM

I'm just shocked :eek: that no naysayers are willing to think for themselves and venture any thoughts about the technical merits of Risch's idea. The simple possibility that Risch's approach might prove to provide another measurement aspect that could help to quantify the sound of a component is reason enough to be excited about it. But, drawing that conclusion relies on independent thinking instead of on edicts from external authorities, so maybe I shouldn't be surprised about the lack of response.

If a suspected quack gives me a diagnosis, it might SOUND convincing but, not being a doctor, I'd get at least one second opinion before buying into it. As a layman, I wouldn't know technobabble from the truth. Must laymen would admit the same, unless they were under said quack's thrall.

Now, since you mentioned the AES is getting involved, we've got a whole roomful of second opinions to look forward to. Where are they? What did they say?

But, since the copyrights seem to be from 1997 - 2001, I'd say this is either old news or has already had it's day in the sun and dried up like a day old dead fish on a Bahamian dock.

gonefishin

08-30-2004, 05:47 PM

E-Stat

08-30-2004, 05:50 PM

...has come up with what is apparently a new approach to testing distortion in audio components, and he seems to suggest that he's submitted a paper about it to the AES.
Personalities aside, I anxiously await the time for when there are meaningful, readily available metrics available that fully quantify the performance of audio components.

rw

FLZapped

08-31-2004, 07:30 AM

Jon Risch has come up with what is apparently a new approach to testing distortion in audio components, and he seems to suggest that he's submitted a paper about it to the AES. His description and explanation of the approach begins here: http://www.geocities.com/jonrisch/page10.htm

This is not new. Look at the "copyright" notice. This is a work that proves nothing. he gives an erroneous impression about current measuring methods, so lets clear that up:

1) You can ONLY merasure harmonic distortion with a single test signal.
2) You ONLY need 2 test signals to measure IM.

What are 31 going to do for you?

He came up with this methodology to support his belief in bi-wiring.

If the old(2 years or so) archives were available, you'd see that many holes were shot in this work, including his bi-wiring measurements. You might find some by Steve Eddy at AA, but I doubt their archives go back that far either.

-Bruce

Swerd

09-01-2004, 07:20 AM

I anxiously await the time for when there are meaningful, readily available metrics available that fully quantify the performance of audio components.
I do not consider myself an advanced audio geek nor do I fancy myself an audio philosopher, whatever those are. However, I am a scientist. I make a living by being a scientist. The entire profession is based on both objectivity and skepticism. It weeds out irreproducible and unverifiable results.

I wish I had lab results to share about any of these, but I don't work on any of these subjects professionally:

transmission properties of audio frequency low voltage AC signals through cables
possible differences in audibility that stem from different cable designs
neurophysiology of the perception and processing of sound by the ears and audio cortex

In a nutshell, that is the problem with the great cable debates on this forum. Probably only very few scientists (at best) work on these subjects. More likely, no one works on the first two. It's not exactly cutting edge science. The last time this was of major interest was when the Bell Labs studied the losses in telephone voice signals due to very long wire lines. That was more than 50 years ago. If anyone knows something more recent, please tell us. Bell's solution to the problem was to adopt microwave frequency carrier waves as a long distance transmission method instead of copper wire. The audio frequencies of the human voice are only the midrange of the 20-20 kHz audio spectrum and the very long length of wires involved in telephone transmission don't compare at all to the short lengths we use for home audio. So it could be said that very little is known on this subject. Research on the third subject is somewhat more active today, but it focuses on hearing speech and processing language and treating various forms of hearing and speech disorders.

Research science is driven by the availability of money. There is no government agency or private industry that thinks that these fields are major unmet needs worth the expenditure of research funds.

So to the anxious E-stat, I would say be patient. It may be a very long time before that happens.

Swerd

09-01-2004, 07:46 AM

Jon Risch has come up with what is apparently a new approach to testing distortion in audio components, and he seems to suggest that he's submitted a paper about it to the AES. His description and explanation of the approach begins here: http://www.geocities.com/jonrisch/page10.htm

Views?
Spews?
What say yous? This was presented at the annual AES meeting in 1998. See http://www.aes.org/publications/preprints/preprints_search.cfm. (search under Author Names: Risch, Jon M.) He did not follow up with more work using this method or further development of it, and it has apparently attracted little or no interest among others since.

You should be aware that there is a major difference between presenting at the AES meeting (what the AES calls a "preprint") and publishing a paper in the Journal of the AES. Only the journal papers receive scientific peer review, while the presentations at the annual meeting are taken as a preliminary report. Risch has only presented his work at the meetings and has apparently never published them in the Journal of the AES.

markw

09-01-2004, 06:36 PM

E-Stat

09-01-2004, 07:29 PM

So to the anxious E-stat, I would say be patient. It may be a very long time before that happens.
I can be patient for what some believe has already come to pass.

rw

Swerd

09-02-2004, 07:33 AM

…for what some believe has already come to pass.
There are frequent anecdotal reports of listeners who claim to hear differences in sounds of audio playback systems due to different cables in the system. The standard measurements of cable electrical properties, accepted by the electronics industry at large, fail to explain these perceived differences.

If you have new information to add to this, as your comment suggests, we are all eager to hear it.

E-Stat

09-02-2004, 08:11 AM

There are frequent anecdotal reports of listeners who claim to hear differences in sounds of audio playback systems due to different cables in the system. The standard measurements of cable electrical properties, accepted by the electronics industry at large, fail to explain these perceived differences.

If you have new information to add to this, as your comment suggests, we are all eager to hear it.
I am unaware of any empirical evidence to support either position for when the question is not limited to basic consumer level equipment.

rw

J Risch

09-13-2004, 09:35 AM

Chairman Jon???????

First, for those who have not had access to my AES paper on the Phi Spectral multitone, I have placed a text-only copy here:
http://www.geocities.com/jonrisch/PhiSpectral1.htm

While the text copy provides sufficient information and data to understand the concept behind the idea, the graphs and measurement results are a huge aid to understanding what is going on, if one is familiar with spectrum analysis results.

If anyone is interested in seeing the extensive graphics, then they can e-mail me at j_risch@bellsouth.net, and request the PDF of the paper. Be warned the PDF is approx. 3.4 Meg, so it is not recommended for regular phone line connections! If you are in this situation, and would like a copy, e-mail me, and we can work out a snail mail solution.

Second, let me say that there have been some folks at the old AR that claimed they read and comprehended my AES paper on the Phi Spectral multitone signals. However, it became clear, that some had either not actually read the paper, or that they had failed completely to comprehend it, based on criticisms and comments they made.

This is not surprising, I have found that folks either "get it" and realize what a boon this is to measurement SOTA, or they don't get it, and invariably act as if it is some sort of boondoggle, and totally unnecessary.

With that in mind, I will respond to some specific points made here in this thread, referring to them as quotes in brackets.

.
Music(as most musicians know) is a series of mathematical relationships...so when it is mentioned that this "new" test is not comprised of "multiples" of what practical application is it?..

I deliberately and specifically use a non-harmonic sequence for the reason given in the paper, to avoid the inevitable cover-up of the distortion products that such a signal would cause. You appear to be postulating that because the test signal does not replicate the harmonic structure of music, that it would somehow not be relevant.

This kind of thinking would then invalidate all the other common test signals used, because none of them replicate the harmonic structure of music either. Single continuous sine waves used for HD and THD measurements do not have a harmonic structure, the IM measurements using two tones do not, etc. Most folks familiar with the reasoning behind and the use of the current test signals would be able to address this point, so I will not belabor it here. Suffice it to say, through the use of more than just one or just two pure sine waves, the Phi Spectral multitone is closer to real music in stimulating the DUT with a much more complex signal, one that has a higher crest factor than any of the more traditional tests.

.
Is this tone played as though it were a "chord"?...is it a series of arpeggiated tones, which would simply make it the oft-discounted "test tones"

It can be many things, but what I proposed and measured in my paper were a more or less continuous tone, consisting of either 6, 10 or 12 pure sine wave tones, at frequency spacings that are not harmonically or common integer fractional related (this latter meaning 1/3 octave spacing, or 1/2, or 1/4, etc.).

.Perhaps, the "squeaky clean" recorder isn't...What protocols were followed to be quite certain the source material itself isn't contaminated in some way?

Aside from the fact that I am a professional, and have taken the numerous steps necessary to assure that no such errors occurred, I can say specifically on this particular point: that the test signals were generated in the digital domain, using what was then Cool Edit, these wave files can then be directly analyzed within Cool Edit to see what the spectral content is.

In addition to this, the wave files were burned to a CD-R. This CD-R was then played back in a variety of CDP's, and the output of these CDP's was sent ot a spectrum analyzer, and the test signal studied and analyzed. Once a suitably clean CDP was selected, the signal was run through a mixer used to set levels, and thus the mixer was checked for distortion and contamination. Other measurements that were not all electrical, such as the speaker distortion tests, were performed using accepted industry techniques, using well known instruments and tools, such as ACO and Larson Davis, etc.
I do want to note that ALL of the forgoing information was stated in my paper.

"so much for all CDPs sound alike"...Who ever said that? It has been said transports read ones and zeros...that error correction and such is fairly identical...after all I think it's SONY and Philips who arrived at the standard and who produce the vast bulk of the transports used...the output is then "tweaked" to provide the specific "sonic signature" each manufacturer thinks they can sell.

I think you have a very distorted and simplistic view of how a CDP works, and what is going on internally.

The various transports and laser assemblies all have varying abilities to read the discs, some can sail through damage and obscuring materials like fingerprints, and others can stutter and choke on the slightest deviation from perfection. So even the ones and zero's sometimes do not make it out perfectly. Aside form that, once we have the digital data stream recovered from the transport, it has to go several places before it comes out as an analog signal, you make it sound like the transport data is connected directly to the manufacturer's "tone controls". Not quite that simple.

The raw disc data has to be digitally filtered, and then this filtered digital signal is passed on to the DAC, which provides the analog output to the output stage.

The digital filtering is one of the areas where there is a lot of variations on what amounts to nearly the same textbook/traditional measurement results, but a lot of variation in terms of other parameters. Since the AES paper, I have verified that the digital filter in some CDP's clips on complex signals when they get within 3-6 dB of 0 dBFS. This was verified to be the result of the digital filter, by using a CD-R with various levels of the Phi Spectral test tone, and by monitoring the output stage for clipping levels etc., including injecting suitable levels of analog signals to see at what level the output stage did clip by itself.

So my new test signal has already shown results which can not be obtained via the more traditional test signals, even including most of the multitone test signals in use prior to my signal.

Jon Risch
(now posting as J Risch)

J Risch

09-13-2004, 09:41 AM

...wrapped up in scientific sounding mumbo jumob that was essentialy ignored by those in the know. comic relief at the convention perhaps?

But, I'm sure the simple minded who want to believe in him will take great pride in his words and be suitibly impressed. Impressed enough to tout this as another of his great breakthroughs.

A true victory of idol worship and wishful thinking over reality.

This reply addresses comments made by both markw and swerd in this thread.

First, it may not be common knowledge, but for the last 12-15 years, the AES has had many more papers submitted than there are time and space for presentation at an AES conference. At the one I presented at, where I gave TWO papers, the ratio of submitted papers to slots available was at least two to one, that is, there were twice as many papers submitted than there were time slots available to present them in.

Thus, my paper was pre-selected in order for me to even be able to present it at all. One way of looking at this, is that I had already passed a criterion where my paper was deemed to be in the top 50% of the AES membership, or it never would have been given.

Publication in the AES journal has a whole different set of criteria, not all of which are obvious and not all of which are wholly related strictly to merit (or the technical "goodness" or "utility"). It may come as a shock to some (but not those who belong to other professional societies or organizations), that some of the process is unavoidably political, and to some extent, based on who knows whom.

It may come as another shock to some, that I am not exactly one of those who has sought to curry favor and provide for my own advance in the ranks of the AES, and have even made some enemies within the ranks of the old school engineering clique. It is not too hard to figure out that given these circumstances, my paper was not rushed to the front of the line, nor was it necessarily considered impartially for ultimate publication.

In any case, just because I have not publically published any further work on the signal, does not mean it has withered away.

Over the years, I have been contacted by engineers and scientists from all over the world, concerning the details and specific questions about my test signal, and know that at least a some time over the last 5-6 years, that researchers from Denmark, Japan, Germany, Poland, Norway, Hong Kong and Taiwan have used it to investigate various audio components, as well as various companies in the US, including Klipsch, Cerwin-Vega, and several others. My paper has been referenced over a dozen times that I know of, because the authors contacted me at one time or another.
These are just the folks that I know about, there are likely to be many others using one form or another of the Phi Spectral signal, and they have not made it public or contacted me.

I have come up with new versions of the test signal, and have been working to incorporate some sort of weighting scheme to weightt he order of the distortion product, and display it so as to make it easier to interpret the spectrum analysis results.

Jon Risch

J Risch

09-13-2004, 09:51 AM

This is not new. Look at the "copyright" notice. This is a work that proves nothing. he gives an erroneous impression about current measuring methods, so lets clear that up:

1) You can ONLY merasure harmonic distortion with a single test signal.

This is not true at all, and shows a complete lack of understanding of measurement techniques and FFT capabilities.

In the simplest form of rebuttal, all one has to do is look at any one of the common two tone IM test signals, run them into an FFT spectrum analyzer, and one can see the harmonics of the two test tones, separate and distinct from the IM products.

In order to do this with multiple tones, one MUST take an approach such as I do, or harmonic cover-up will become a distinct problem.

2) You ONLY need 2 test signals to measure IM.

Again, not true, and rather simplistic as well.

With HD, we can actually run a swept sine wave at a certain slow enough speed (to match the frequency resolution of the measurement), and measure the various harmonics all across the audio band. This results in the typical HD vs. frequency plots which are generated, showing the level of the fundamental, and the relative levels of the various order of harmonic distortion at the frequency of the fundamental.

However, with a simple two tone IM, all we can look at is the fixed IM products that result from those two particular frequencies.

There are only a few internationally recognized sets of two tone IM frequencies:
The classic SMPTE set of 60 Hz and 7 kHz, with the 7 kHz component at -12 dB relative to the LF tone.
The DIN set is at 250 Hz and 8 kHz, and the CCIF set is at 19 kHz and 20 kHz, both sets with the tones at equal levels.

None of these will allow you to see how the DUT reacts to any other than the specific frequencies they use. Period.

In theory, one could make all three measurements, and glean some additional data, but it would still be limited to the sum total of the frequency set discrete results involved, and nothing more.

Overall, one pass with the Phi Spectral, and you have a measurement of HD for 6, 10 or 12 tones, which for EACH of these original pure tones, you can check for harmonic distortion products out to the limts of the spectrum analyzer without the other tones "stepping on" top of them AND you can ALSO check for ALL the IM products that can exist due to the simultaneous presence of 6, 10 or 12 tones, which is a considerable number, even if we only consider limiting our search to orders below the 4th.
Given that any of the versions cover a wide range of the audio band, you can now look at HD and IM over a wide range of frequencies, with simultaneous stimulus, which is more like music than just single or two tone stimulus.

What are 31 going to do for you?

This is actually kind of funny, as none of the test signals I proposed had 31 tones in them. This might be referring to the Audio Precision FASTTEST multitone signal, which has 31 simultaneous 1/3 octave spaced tones in it. However, this test signal falls prey to the very problem I point out in my paper, and that my signal was designed to address: that of the extensive cover up and obliteration of so many of the potential distortion products that might be generated, but would never be seen in a spectrum analysis, due to the spacing interval used. I argue for the limitation of how many pure tones are present, for what I feel are some very compelling technical reasons.
Thus, I recommend an upper limit of 12 tones, as a useful compromise number between full band coverage, and limited dynamic range and overwhelming spectral clutter.

If the old(2 years or so) archives were available, you'd see that many holes were shot in this work, including his bi-wiring measurements.

It is unfortunate that the old AR pages and archioves are essentialy gone, because then we could all see that what some of the folks here were calling rebuttal, was in fact, just a lot of handwaving and unsubstantiated claims on their parts, including misunderstanding what the test signal was about, and the details concerning it's use and interpretation. FLZapped was one of those who did all of the above, but none of it was what any reasonable person would call "shooting holes" in it. Just a lot of carryng on, primarily because it was me that was involved.

Jon Risch

ToddB

09-13-2004, 10:36 AM

But since you asked in an oh, so confrontationally condecsending tone, here goes...

Sorry, my post does come off sounding more contentious than I intended.

And then of course there is, what I consider "editorializing" in a what is ostensibly a "tech" article, "so much for all CDPs sound alike"...Who ever said that?

"All CDPs sound alike" was the standard line prior to jitter being identified and quantified. But yeah, once it was, and it was found to be audible, not many people bother to make that argument anymore. The principle that something can be heard by a large number of people before it can be measured seems to be lost on many when it might also apply to other components, like cables for example.

Then of course there is mention of the contingent who will refuse to believe his results...

Assuming that the measurements are correct, I would think that the next step would be to determine if the measurements correlate not with belief, but with listening experience. That, of course, is a whole 'nother can of worms.

As was admitted in the article, the author doesn't even seem to have any real conclusions, only the hope that his work might be the basis for further investigation...

Maybe in the strictest sense, but as I read it, the measurements resulting from the test method are themselves the conclusion.

Anything provided here is just so much idle chatter, more hits for E-centives and not much more

If you think I started this thread to generate hits and some empty idle chatter, you are mistaken.

jimHJJ(...be careful what you ask for...)

Actually, I thought your response was fairly thoughtful, and though I disagree with most of your conclusions, I appreciate the perspective.

Sir Terrence the Terrible

09-13-2004, 10:55 AM

First, it may not be common knowledge, but for the last 12-15 years, the AES has had many more papers submitted than there are time and space for presentation at an AES conference. At the one I presented at, where I gave TWO papers, the ratio of submitted papers to slots available was at least two to one, that is, there were twice as many papers submitted than there were time slots available to present them in.

Thus, my paper was pre-selected in order for me to even be able to present it at all. One way of looking at this, is that I had already passed a criterion where my paper was deemed to be in the top 50% of the AES membership, or it never would have been given.

Publication in the AES journal has a whole different set of criteria, not all of which are obvious and not all of which are wholly related strictly to merit (or the technical "goodness" or "utility"). It may come as a shock to some (but not those who belong to other professional societies or organizations), that some of the process is unavoidably political, and to some extent, based on who knows whom.

While I cannot attest to the other information in Jon's post, this part of it I know he is telling the truth on. AES has in the past, and continues to be a VERY political organization. It is also plagued with the good ol'e buddy mentality. I know a couple of engineers who have submitted papers years ago countering information presented by members affiliated with the AES for many years . These papers have been examined, but not published Only God himself knows if this information ever will

ToddB

09-13-2004, 10:57 AM

The information contained on those web pages of Jon Risch is not extensive enough to draw any conclusions. I sincerely hope he does come up with a measurement method that more closely analyzes what is going on in a cable.

And like all yeasayers decree, the proof is in the listening. Therefore, when a test shows conclusively that an audio cable is causing distortion, then it will be necessary to determine if that distortion is audible. And that means a controlled listening test.

I can't speak for everybody, but the results of a listening test with correlation to cable distortion is the first point in time I would spend any effort in a detailed analysis. And then the big step would be to determine which cables can reduce audible distortion. That is really what we are interested in, is it not?

Absolutely. For my purposes as a hobbyist, I personally would be comfortable knowing how anecdotal listening experiences correlate to the test measurements, and then finding out if my own listening experience agrees with others', but that standard will obviously not be sufficient for everyone. If a listening test methodology could be arrived at that satisfied the concerns of both the yeasayer and naysayer camps, then information from such a test might be useful to me as well.

FLZapped

09-13-2004, 10:59 AM

This is not true at all, and shows a complete lack of understanding of measurement techniques and FFT capabilities.

In the simplest form of rebuttal, all one has to do is look at any one of the common two tone IM test signals, run them into an FFT spectrum analyzer, and one can see the harmonics of the two test tones, separate and distinct from the IM products.

Exactly. How is this a rebuttal again? It is exactly what I said; Two tones and you get Intermodulation products of a non-linear device.

Again, not true, and rather simplistic as well.

With HD, we can actually run a swept sine wave at a certain slow enough speed (to match the frequency resolution of the measurement), and measure the various harmonics all across the audio band. This results in the typical HD vs. frequency plots which are generated, showing the level of the fundamental, and the relative levels of the various order of harmonic distortion at the frequency of the fundamental.

Exactly, but why bother to sweep, either you are going to see harmonic distortion generated by the non-linearities of the device, or you aren't. Or are you trying to talk about electro-mechanical devices without saying so? Regardless, the premis of the test is still exactly the same.

However, with a simple two tone IM, all we can look at is the fixed IM products that result from those two particular frequencies.

Of course, that is the very purpose.

There are only a few internationally recognized sets of two tone IM frequencies:
The classic SMPTE set of 60 Hz and 7 kHz, with the 7 kHz component at -12 dB relative to the LF tone.
The DIN set is at 250 Hz and 8 kHz, and the CCIF set is at 19 kHz and 20 kHz, both sets with the tones at equal levels.

None of these will allow you to see how the DUT reacts to any other than the specific frequencies they use. Period.

So? Either you are generating IM products, or you are not. If your device being tested is non-linear, you will have distorion products, period.

In theory, one could make all three measurements, and glean some additional data, but it would still be limited to the sum total of the frequency set discrete results involved, and nothing more.

In theory, ahhhh, I see. As usual, you haven't actually done it. Like all the rest of your "theories" that remain unproven. So tell me about those 180 degree phase reversals in a 5 foot coaxial cable at audio frequencies again......

Overall, one pass with the Phi Spectral, and you have a measurement of HD for 6, 10 or 12 tones, which for EACH of these original pure tones, you can check for harmonic distortion products

As you can with a single tone and not have to distinguish between what are IM products and what are harmonic products.

out to the limts of the spectrum analyzer without the other tones "stepping on" top of them AND you can ALSO check for ALL the IM products that can exist due to the simultaneous presence of 6, 10 or 12 tones, which is a considerable number, even if we only consider limiting our search to orders below the 4th.

As you can with two tones. Extra tones don't give you better results, just more complex version of the results that may not be able to be interpreted.

Given that any of the versions cover a wide range of the audio band, you can now look at HD and IM over a wide range of frequencies, with simultaneous stimulus, which is more like music than just single or two tone stimulus.

Once again, you are going to generate intermodulation products if your device is non-linear, period. Two tones is all that is required to predict and see all products.

Take a look at the second page of this document, it gives an explaination and the mathmatical relationship to both Intermodulation Distortion and Harmonic Distortion:

http://www.us.anritsu.com/downloads/files/11410-00257a.pdf

Here is another, which talks about Harmonic Distortion and below it, Intermodulation Distortion:

http://hyperphysics.phy-astr.gsu.edu/hbase/audio/amp.html#c3

And what do they both use? A single tone for Harmonic Distortion and two tones for Intermodulation Distortion.

Making something more complex does not necessarily make it better.
Any electrical engineer will tell you as you add more test signals, the more the results are going to look like noise.

-Bruce

ToddB

09-13-2004, 11:15 AM

Personalities aside, I anxiously await the time for when there are meaningful, readily available metrics available that fully quantify the performance of audio components.

I fully agree. It will make things so much easier.

ToddB

09-13-2004, 11:24 AM

Research science is driven by the availability of money. There is no government agency or private industry that thinks that these fields are major unmet needs worth the expenditure of research funds.

One exception to this might be the very audiophile companies who are making the products. Given that it would not be in their competitive best interests in the marketplace to release any data they had found to be useful, I could see how we might not hear anything about it.

jneutron

09-13-2004, 11:38 AM

One exception to this might be the very audiophile companies who are making the products. Given that it would not be in their competitive best interests in the marketplace to release any data they had found to be useful, I could see how we might not hear anything about it.

That is a double edged sword..

They will not publish anything useful unless they can patent it to protect IP..and they will not publish results which counter their claims..

I know a couple of engineers who have submitted papers years ago countering information presented by members affiliated with the AES for many years.

And people wonder why I don't publish my test results and analysis which proves Hawksford's skin article wrong...go figure..I certainly wouldn't waste my time trying to submit it, as H is up there in AES.....

Cheers, John

ToddB

09-13-2004, 11:47 AM

As you can with two tones. Extra tones don't give you better results, just more complex version of the results that may not be able to be interpreted.

Making something more complex does not necessarily make it better.

But music almost always consists of more than two tones, and if a test that introduces additional tones reveals distortion characteristics that differ from those that are measurable using only two tones, wouldn't that test theoretically better reflect the ability of a device to accurately reproduce music? I would tend to think that it does, and that it's to our advantage to know and account for this, assuming that the distortion character revealed with a complex signal is found to be audible.

ToddB

09-13-2004, 12:03 PM

That is a double edged sword..

They will not publish anything useful unless they can patent it to protect IP

Agreed.

..and they will not publish results which counter their claims..

Are you suggesting that marketing at some companies takes precedence over engineering? :eek:

LOL...

FLZapped

09-13-2004, 01:02 PM

But music almost always consists of more than two tones,

Which is one of several reasons why it isn't used for test measurements.

and if a test that introduces additional tones reveals distortion characteristics that differ from those that are measurable using only two tones, wouldn't that test theoretically better reflect the ability of a device to accurately reproduce music?

No.

-Bruce

ToddB

09-13-2004, 03:09 PM

Which is one of several reasons why it isn't used for test measurements.

I'd think that music would be the ideal test signal, given that it's the signal the equipment is dedicated to reproducing, IF the overlapping of fundamentals and harmonics could be avoided, which is obviously not possible. That's why Risch chose the specific frequencies he used in his test tones, which seem to be attempts at compromising between mimicking the complex behavior of musical signals, while still being simple enough to provide discrete values to measure.

No.

Do you have an explanation for why not?

skeptic

09-13-2004, 03:29 PM

I have decided to suspend my boycott of AR resulting from its new censorship policies making this exception. I have argued with Mr. Risch on this board in the past and the debates between us have been long and sometimes heated. As far as I can tell, he stopped posting here several years ago when I exploded every one of his theories about audio cables and power wires using simple logic, and his own words. That demonstration of my proof of his inconsistency and illogic should still be available in the archive should anyone care to find it and read it. I won't go into it now as it is a long dead debate as far as I am concerned.

Reading the current debate, it seems little has changed. Mr. Risch IMO has invented a new self serving illogical and inconsistent method for measuring non linear distortion which of course he immediately applies to justify his apology for the after market audio cable industry. It begins with incorrect assumptions, forces them together with faulty logic, is supported with subjective impressions and reaches a contrived conclusion which was IMO pre determined to once again justify his discredited views, at least in my opinion, on audio cables.

"Traditional test signals either use a single sine wave tone or at most, a pair of tones, to explore simple harmonic distortion, and simple IM distortion. Music is composed of many tones, all happening at once, and with varying relationships."

There is no such thing as simple harmonic and simple IM distortion. There is only harmonic and IM distortion. Denying that the use of one or two tones at a time is a valid way to predict how electronic devices will process more complex waveforms such is music is a denial of the well established principle of superposition as well as Fourier and Laplace analysis. It rejects over 100 years of accepted mathematical and theory scientific experience. It is a false argument.

"I realized that if you make all the tones fall at intervals where they would not have the same spacing ratio's, and would not have the same frequency intervals, this would avoid the cover-up of the distortion products. "

IM and Harmonic distortion is successfully and repeatedly measured to tens of thousandths of a percent, far lower than any human being can hear. There are no cover-ups. The existing science is not flawed or inadequate. At least there is no evidence of that here. The false arguement appeals to non technical neophytes, not engineers.

"The correlation between which unit sounded good, and which didn't followed the Phi Spectral measurements almost exactly."

This is a purely subjective statement which has no value in a scientific discussion. It is typical of the flawed reasoning frequently offered as statements of fact in Mr. Risch's presentations.

"I hypothesized that for bi-wired speaker cables, the big difference would be in the current flow, as the impedance's of the crossover would create a preferential situation with regard to the flow of current in the woofer cable vs. the tweeter cable."

This entire part of this presentation is based on a completely flawed assumption. As I have stated elsewhere, bi-wiring may have a theoretical justification but not the one usually presented which is that somehow different speaker cables are more suited to carry different frequencies or that somehow there is an interaction inside the cable with current at different frequencies which causes an undesired interacton. Current density in audio cables is infinitesimally low compared to what would be required to compromise the linearity of cables to handle current at different frequencies to the point of interactive distortion. The simple proof of this is the example of twisted pairs of telephone cables which can carry hundreds of multiplexed telephone conversations on different subcarrier frequencies where the current denisity is comparable to that of a speaker cable and each phone conversation is as clear as if there was only one.

If there is a justification for bi-wiring loudspeakers it is simply this. With bi-wiring, the amplifier's low impedance output stage is interposed electrically between the woofer which may generate substantial back emf and the midrange or tweeter. The amplifier would act to shunt current from this back emf before it reaches the other drivers much more effectively than would otherwise be the case. In a fair test, not only would the loads have to be completely passive but the combined gage (cross-sectional area ) of the woofer and tweeter wire would have to be equal to the single wire of the non bi-wired arrangement.

To suggest that Mr. Risch's method has some innovative insight is to assume that every one of the countless hundreds of thousands of mathematicians, electrical engineers, scientists, and technicians who have developed, used, and trusted test measurements and equipment over the last 70 to 80 years has overlooked an obvious theoretical flaw or ignored it.

It is also highly self-serving to defame professionally recognized international technical bodies such as the AES or IEEE by saying that they have rejected Mr. Risch's technical papers in the past because of political considerations. They were certainly rejected because of their technical flaws but even if they are accepted, that does not prove the usefulness or even validity of his theories, only that they don't have obvious fatal errors. It would be for the profession to develop and uses the proposed methods as a substitute for the existing methods as a demonstration of their innovative value.

BTW, if one actually were looking for frequencies to use in combination having the criteria Mr. Risch desired, the logical place to look is to prime numbers. Prime numbers are not evenly divisible by a whole number except by one and by themselves.

RobotCzar

09-13-2004, 04:25 PM

“Traditional test signals either use a single sine wave tone or at most, a pair of tones, to explore simple harmonic distortion, and simple IM distortion. Music is composed of many tones, all happening at once, and with varying relationships.”

There is no such thing as “simple” harmonic and “simple” IM distortion. There is only harmonic and IM distortion. Denying that the use of one or two tones at a time is a valid way to predict how electronic devices will process more complex waveforms such is music is a denial of the well established principle of superposition as well as Fourier and Laplace analysis. It rejects over 100 years of accepted mathematical and theory scientific experience. It is a false argument.
.

Are you reading this E-stat? You are way, way off base in swallowing the high-end claims about "simple" test signals. I have tried to make this point to you, but you, like JR. know that if one card is removed from you house-of-cards belief system, the whole thing will collapse. Your "experience" is not an issue that anyone should care about, especially when it is irrational in light of simple scientific and mathematical facts.

Jon Risch is demonstrating a lack of understanding of extremely basic physical principles. Why would anybody give two hoots about what he says about his "discoveries"?

Why embrace ignorance?

E-Stat

09-13-2004, 04:39 PM

Scratch the sarcasm. Please provide the proof for your assertion concerning the audibility claim.

IM and Harmonic distortion is successfully and repeatedly measured to tens of thousandths of a percent, far lower than any human being can hear. There are no cover-ups. The existing science is not flawed or inadequate

rw

E-Stat

09-13-2004, 04:51 PM

You are way, way off base in swallowing the high-end claims about "simple" test signals.
I really do try to put myself in your shoes when I read comments like that. You relate from a completely different, detached point of view. You know what you've read. I know what I have experienced.

rw

skeptic

09-13-2004, 05:18 PM

Sarcasm as a personal insult is the last resort of someone who cannot argue the facts.

This is the laboratory board where scientific principles are supposed to be the topic of discussion, not personal prejudice. It is especially inappropriate for someone who has been assigned the function of impartial moderator. This is reason enough for me to have stopped posting here.

E-Stat

09-13-2004, 05:25 PM

It begins with incorrect assumptions, forces them together with faulty logic, is supported with subjective impressions and reaches a contrived conclusion which was IMO pre determined to once again justify his discredited views, at least in my opinion, on audio cables.
Your opinion is twice noted.

rw

J Risch

09-13-2004, 06:19 PM

[

Exactly. How is this a rebuttal again? It is exactly what I said; Two tones and you get Intermodulation products of a non-linear device.

Actually, I was providing an example of how two tones can also provide the harmonic distortion information too. You missed the mark entirely there Bruce.

In any case, the scenario I describe is trivial, and it shows that you can indeed garner HD data from a test signal with more than one tone in it. Thus your statement: "1) You can ONLY merasure harmonic distortion with a single test signal." has been shown to be incorrect.

Exactly, but why bother to sweep, either you are going to see harmonic distortion generated by the non-linearities of the device, or you aren't. Or are you trying to talk about electro-mechanical devices without saying so?

This is at the crux of the matter here, and why both you and skeptic are way off base. With you Bruce, having an RF background, it is understandable that you look at things from such a background.
RF amps are designed a certain way, and have to deal with a very limited frequency range in terms of percentage of an octave band. Their distortion behavior is much more predictable and can be predicted by some simple equations relating level to an amount of 2nd or 3rd order distortion, hence the "2nd order intercept point" and the "3rd order intercept point" can be predicted and plotted.

Within these contraints, measurement at a single frequency may suffice to characterize the amps distortion behavior. If it has a certain 2nd order intercept point for 14.7 MHz, then for 14.2 MHz, it will behave virtually identical.

By the same token, this very predictable behavior also allows one to use a very simple two tone IM measurement to investigate the various orders of IM distortion. In such a simple and well defined amp, it is even possible to tie the HD and the IM distortion predictions together, and predict one from the other, if certain basic precautions are taken.

However, with audio, ALL BETS ARE OFF! You CAN NOT use this same RF experience to approach and measure audio devices! If one were to believe skeptic, then this would violate several laws of physics, and cause the universe to be sucked into a black hole or an equally catastrophic event.
The plain fact is, many audio amplifiers DO NOT behave this predictably, and measuring the HD at one frequency DOES NOT PROVIDE A GOOD IDEA OF WHAT IT WILL DO AT ANOTHER FREQUENCY.

The simplest proof of this is any decent power amp review that includes a harmonic distortion measurement at more than one frequency, or an HD measurement that sweeps the audio band. Quite simply, if what Bruce and skeptic say is true, then the distortion would not vary across the audio band, it would remain a constant value, all the way from 20 Hz, to 20 kHz. Guess what? It ain't so. A great many audio amplifiers exhibit higher harmonic distortion at the frequency extremes than at say, 1 kHz.

This simple fact is all that it takes to completely blow FLZapped and skeptics tirades out of the water. Bruce with his insistence that "You can ONLY merasure harmonic distortion with a single test signal.", and skeptic with his "Denying that the use of one or two tones at a time is a valid way to predict how electronic devices will process more complex waveforms such is music is a denial of the well established principle of superposition as well as Fourier and Laplace analysis."

That's the ball game right there.

Or are you trying to talk about electro-mechanical devices without saying so?

No, but we can not ignore them, just because they also throw any such dogma about predicting the distortion behavior well enough that only one frequency would suffice to fully characterize the HD of an audio device, or that one set of frequencies would suffice to fully characterize the IM all across the audio band. Speakers, mics, headphones, these all can have highly non-linear behavior that defies any such predictions and assumptions.

This pretty much takes care of the vast majority of both FLZ's and skeptic objections and comments.

In theory, ahhhh, I see. As usual, you haven't actually done it. Like all the rest of your "theories" that remain unproven.

Actually, I was speaking of someone in the third person, for myself, I have indeed made all three measurements, and they all came up different on speakers, power amps, CDP's, etc. but none were as revealing as my Phi Spectral test signal.

As you can with two tones. Extra tones don't give you better results, just more complex version of the results that may not be able to be interpreted.

So, because a more powerful test signal is harder to interpret, we should just give up and not use it? That hardly sounds very scientific or searching to me.

Making something more complex does not necessarily make it better.
Any electrical engineer will tell you as you add more test signals, the more the results are going to look like noise.

Indeed, and you confused this very issue the first time around here at AR. You said that the distortion products were "the noise floor", when in fact, they were a lot of distortion products being generated.
However, the whole big deal with my new test signal is that YOU CAN FIGURE OUT WHERE THEY CAME FROM _and_ none of them are readily covered up by any of the others. That is the power of the Phi Sepctral, that is the big deal.

Jon Risch

FLZapped

09-13-2004, 06:28 PM

I'd think that music would be the ideal test signal, given that it's the signal the equipment is dedicated to reproducing, IF the overlapping of fundamentals and harmonics could be avoided, which is obviously not possible.

You have just answered your own question.

That's why Risch chose the specific frequencies he used in his test tones, which seem to be attempts at compromising between mimicking the complex behavior of musical signals, while still being simple enough to provide discrete values to measure.

Did you bother to look at those links provided? Think how complicated it is to sort out ALL the IM products from 12 simultaneous signals. It's a factorial type problem. I'll expound:

You have first order products for the following:

f1+/- f2, f1+/- f3, f1 +/- f4,....f1+/-f12
f2 +/- f3, f2 +/-f4, f2 +/-f5,....f2 +/-f12
f3 +/- f4, f3 +/-f5,......f3 +/- f12
.
.
.
f11 +/- f12

That's plus AND minus AND that's ONLY for the first order products! Imagine working this out only through say 5th order products...

Now can you begin to grasp how complicated it is to try and sort out all those distortion products? Why? When all you need are two tones. Either your device is linear and produces no products, or it is to a degree non-linear and does produce products. Easily executed, easily measured, and easily quantified. That's why these tests exist as documented world-wide standards.

Furthermore, as I said, the more you add on test signals, the more it looks like noise. Well, that also means it's harder and harder to find very small products from all the "noise" generated by all those signals convoluted together.

-Bruce

J Risch

09-13-2004, 07:14 PM

As far as I can tell, he stopped posting here several years ago when I exploded every one of his theories about audio cables and power wires using simple logic, and his own words. That demonstration of my proof of his inconsistency and illogic should still be available in the archive should anyone care to find it and read it.

In your dreams you did. BTW, the AR archives that you are referring to are no longer readily available, but I wish they were, because then folks could see that you did no such thing.

Most of what you rail about in this post, I have answered in my reply to Bruce/FLZapped re RF amps and how your overly simplistic assumptions about audio electronics, much less electro-acoustic devices, are incorrect.

The bottom line is, if a single tone would suffice to fully characterize an audio device, the FTC would not have the requirement to state a bandwidth for a distortion measurement, a simple 1 kHz tone would suffice.

Me:
"I realized that if you make all the tones fall at intervals where they would not have the same spacing ratio's, and would not have the same frequency intervals, this would avoid the cover-up of the distortion products. "

IM and Harmonic distortion is successfully and repeatedly measured to tens of thousandths of a percent, far lower than any human being can hear. There are no cover-ups. The existing science is not flawed or inadequate.

However, that does not address what I was talking about in my paper, I was referring to the use of the multitone signals that were in common use up till that point in time, most notoriously, the Audio Precision FASTEST signal, and others like it.

In point of fact, and covered in my paper, the AP FASTTEST signal DOES cover up almost ALL the harmonics, and almost all the IM products, what is left to see are the primarily anharmonic and highly non-linear distortion products, which is fine if the DUT is really terrible, or is prone to highly non-linear distortion like a loudspeaker, but not so fine if we are trying to discriminate between two otherwise fairly well measuring audio devices.

And as I have repeatedly stated, and NO ONE has yet to provide ANY rebuttal to, is that no where are the raw metrics of the thresholds of audibility for HD or the JND's been properly correlated to what we hear with music, and how it would be judged sonically. So stating that some harmonic or IM product is "far lower than any human being can hear" has very little meaning in the real world, and is NOT something one can hang their hat on.

Me:
"I hypothesized that for bi-wired speaker cables, the big difference would be in the current flow, as the impedance's of the crossover would create a preferential situation with regard to the flow of current in the woofer cable vs. the tweeter cable."

This entire part of this presentation is based on a completely flawed assumption. As I have stated elsewhere, bi-wiring may have a theoretical justification but not the one usually presented which is that somehow different speaker cables are more suited to carry different frequencies or that somehow there is an interaction inside the cable with current at different frequencies which causes an undesired interacton.

Quite a few folks seem to have dificulty with this one, even after I have pointed it out in several different ways, and provided a graph of the current flow in the two different wire pairs of a bi-wired speaker.
I show this at:
http://www.geocities.com/jonrisch/page7.htm
I talk about why this is at:
http://www.geocities.com/jonrisch/biwiring.htm

If there is a justification for bi-wiring loudspeakers it is simply this. With bi-wiring, the amplifier's low impedance output stage is interposed electrically between the woofer which may generate substantial back emf and the midrange or tweeter. The amplifier would act to shunt current from this back emf before it reaches the other drivers much more effectively than would otherwise be the case. In a fair test, not only would the loads have to be completely passive but the combined gage (cross-sectional area ) of the woofer and tweeter wire would have to be equal to the single wire of the non bi-wired arrangement.

And I show this in a table at:
http://www.geocities.com/jonrisch/biwiring2.htm
along with the simplified circuit used to derive it.

I have been posting about both issues for a long time now, I guess John Curl is right: first, it doesn't exist, then it was known about all along, then it was invented by us.

To suggest that Mr. Risch's method has some innovative insight is to assume that every one of the countless hundreds of thousands of mathematicians, electrical engineers, scientists, and technicians who have developed, used, and trusted test measurements and equipment over the last 70 to 80 years has overlooked an obvious theoretical flaw or ignored it.

Welllllll, you said it, not me. As I said in my first posted reply to Resident Loser. some folks get it, and some don't. The ones who do are thrilled with the power and capability it offers, and one's who don't are grumbling about how it is not like Grandpa's test signals, darn newfangled high-falutin computers and FFT's!

They were certainly rejected because of their technical flaws ...

We have yet to see WHAT technical flaws you are talking about, since none of what you have posted so far made a serious attempt to explain what is flawed with the Phi Spectral multitone test signal, other tha your OWN flawed interpertation of the validity of the use of a single test tone (or a single pair of tones for IM) to fully characterize the distortion in an audio amplifier.

BTW, if one actually were looking for frequencies to use in combination having the criteria Mr. Risch desired, the logical place to look is to prime numbers. Prime numbers are not evenly divisible by a whole number except by one and by themselves.

I actually looked into that, but found that I still wanted to have a more consistent criteria for the selection of the primary test tone frequencies, and how do you choose the approximate spacing of these prime numbers? Within the limitations of the FFT bins, it would have been too easy to fall into the same "equal spacing" trap that ended up with several or more of the prime number tones at spacngs that would end up covering up a harmonic or an IM product.

BTW, the criteria for a prime number does not preclude that it can not cause various distortion products to fall on top of one another, because these distortion products are multiples of the prime number, and cross-products, etc., so it is not certain that they would not tend to do so at some higher order of distortion.
Note that is it is NOT immediately obvious what MIGHT get covered up, just by an inspection ofthe primary frequencies, and even with a sophisticated spread sheet, and numerous analysis runs, it is hard to be sure that you are not inadvertantly covering up some product or another, without going over each potential possibility. The Phi multipliers I used at least have some mathematical assurance behind them, in terms of providing the least amount of distortion product cover up.

Jon Risch

J Risch

09-13-2004, 07:21 PM

Jon Risch is demonstrating a lack of understanding of extremely basic physical principles. Why would anybody give two hoots about what he says about his "discoveries"?

Why embrace ignorance?

Indeed, I could ask you the same question.

Exactly what was demonstrated, and how did you come to that conclusion?

Before you answer, it might behoove you to read the replies I have made to Resident Loser, and to skeptic and FLZapped.

Rather than parrot what skeptic said, I want to know precisely where I was demonstrating this lack.

Come on, it should be child's play for you to provide specifics that are just a copy of what skeptic posted..

Jon Risch

FLZapped

09-13-2004, 07:35 PM

Actually, I was providing an example of how two tones can also provide the harmonic distortion information too. You missed the mark entirely there Bruce.

Interesting, trying to use IM as HD, and blame me for your confusion. Right.

In any case, the scenario I describe is trivial, and it shows that you can indeed garner HD data from a test signal with more than one tone in it. Thus your statement: "1) You can ONLY merasure harmonic distortion with a single test signal." has been shown to be incorrect.

What you described by any standard is IM distortion. Not Harmonic distortion. By world-wide recognized standards, harmonic distortion is measured with a single tone and is supported mathmatically. Intermodulaton is measured with multiple tones. These are given definitions that the rest of the engineering world recognizes as a standard, except you, apparently.

This is at the crux of the matter here, and why both you and skeptic are way off base. With you Bruce, having an RF background, it is understandable that you look at things from such a background.

Devices are either linear, or they are not. Either they produce distortion products, or they don't.

The physics don't change with the operating frequency.

RF amps are designed a certain way, and have to deal with a very limited frequency range in terms of percentage of an octave band. Their distortion behavior is much more predictable and can be predicted by some simple equations relating level to an amount of 2nd or 3rd order distortion, hence the "2nd order intercept point" and the "3rd order intercept point" can be predicted and plotted.

And that matters because? You think the physics changes or something? How absurd. IM is IM and HD is HD and it is ALL generated the same way, regardless of operating fequency. If the device is perfectly linear, no products. If it is non-linear, you get distortion products.

By the same token, this very predictable behavior also allows one to use a very simple two tone IM measurement to investigate the various orders of IM distortion.

Again, you think the physics change? Did you miss the fact that your engineering text book doesn't have a seperate section on defining harmonic and intermodulation distortion for audio vs rf?

However, with audio, ALL BETS ARE OFF! You CAN NOT use this same RF experience to approach and measure audio devices!

Please, show us all how the physics of harmonic distortion and intermodulation distortion are generated differently for rf vs audio. Please show us all how can or cannot get f1+/- f2, 2f1+/- f2....nf1 +/- f2 for either rf or audio, please, we're all waiting for the new formula to show us all that the mathmatics that have accurately described intermodulation distortion for SOOOOO many years is suddenly wrong. Please, we're all waiting.

If one were to believe skeptic, then this would violate several laws of physics, and cause the universe to be sucked into a black hole or an equally catastrophic event.

Yet you think it is okay for you to espouse several different laws of physics as to how IM and harmonic distortion are generated at audio vs rf. Yet you say we are violating the laws of physics? I have yet to see you show anywhere which ones are actually being violated. You're just hand waving.

Enough of this squirming around to deflect the real purpose of this discussion:

Your multi-tone test signal is completely unusable to measure intermodulation distortion and is a violation of the recognized definition in measuring harmonic distortion.

Two tones, are all that's needed for IM. Regardless of operating frequency.

Harmonic distortion is measured using a single tone, regardless of operating frequency.

This is recognized world-wide and has been so for a long, long time and no one has proven otherwise. Including you. Even your test signal follows these laws. The problem is, your test signal will generate SO many products it would be impossible to distinguish noise from distortion products making it unusable as a viable test signal.

-Bruce

FLZapped

09-13-2004, 07:45 PM

FLZapped

09-13-2004, 07:49 PM

I really do try to put myself in your shoes when I read comments like that. You relate from a completely different, detached point of view. You know what you've read. I know what I have experienced.

rw

Okay. Then turn on your java and experience these audio illusions:

http://www.cs.ubc.ca/nest/imager/contributions/flinn/Illusions/ST/st.html

http://www.cs.ubc.ca/nest/imager/contributions/flinn/Illusions/TT/tt.html

http://www.kyushu-id.ac.jp/~ynhome/ENG/Demo/illusions2nd.html

Then tell us about how reliable your experience really is.....

-Bruce

E-Stat

09-14-2004, 04:58 AM

And there are people who KNOW thay have seen Bugs Bunny at Disney World....
You still haven't got that right, have you? :)

http://db.audioasylum.com/cgi/m.mpl?forum=prophead&n=996&highlight=bugs+Jitter_by_coffee&session=

rw

skeptic

09-14-2004, 05:31 AM

Mr. Risch;

If you want to overturn 150 years of mathematics and 75 years of laboratory practice based on it, both of which have been accepted universally all over the world, you have to start with an examination of the underlying mathematical principles and the laboratory practices which follow them and show precisely where the equations are wrong or where the instrumentation doesn't conform to the equations. Then you have to present new or modified equations showing why they are right and showing how and why your theory conforms to them. Then, accomplished people in the field with credentials will sit up and take notice. Professional journals have much higher standards and require far more rigorous proof than consumer magazines and internet chat boards. If you want to be taken seriously by them, you must live up to those standards. What is acceptable to a tinkering hobbyist, even one affuent enough to equip a laboratory, sell consumer products, and call himself an engineer, is inadmissable to a PHD in physics or electrical engineering.

FLZapped

09-14-2004, 06:46 AM

You still haven't got that right, have you? :)

http://db.audioasylum.com/cgi/m.mpl?forum=prophead&n=996&highlight=bugs+Jitter_by_coffee&session=

rw

Oh, but I do.

http://www.washington.edu/newsroom/news/2001archive/06-01archive/k061101.html

skeptic

09-14-2004, 07:07 AM

Why should I make any attempt to engage in serious discourse with someone who first insults me, a supposedly impartial moderator no less, then deletes his insult without so much as an apology, and then demands proof for something which anyone with a real technical background in audio would know and understand without question? It was painful enough for me to enter into exchanges with you before you were elevated to "moderator." Power does indeed corrupt, even on the smallest scale.

E-Stat

09-14-2004, 07:10 AM

Oh, but I do.

http://www.washington.edu/newsroom/news/2001archive/06-01archive/k061101.html
Interesting. I guess that is a sad commentary on cultural literacy today. They should have asked a second grader who would know the difference.

rw

E-Stat

09-14-2004, 07:25 AM

Why should I make any attempt to engage in serious discourse with someone who first insults me, a supposedly impartial moderator no less, then deletes his insult without so much as an apology, and then demands proof for something which anyone with a real technical background in audio would know and understand without question?
Absolutely no reason at all. I already know the answer.

Power does indeed corrupt, even on the smallest scale.
As a moderator (as opposed to poster), I will ask you to debate the issues and cease the personal attack you began with Mr Risch. The chest beating opening paragraph was unnecessary. As was my original response to that.

rw

skeptic

09-14-2004, 07:55 AM

I did not attack Mr. Risch on this thread. (That's the one that was deleted by Eric which caused me to stop posting here, remember?) I attacked his theory. Is that also not allowed under the new regime? Isn't that what Todd asked for originally?

"Views?
Spews?
What say yous?"

"I'm just shocked that no naysayers are willing to think for themselves and venture any thoughts about the technical merits of Risch's idea."

Maybe he was disingenuous. Maybe he didn't want a real discussion after all. Mabye he was just pretending.

As for you, I'm still waiting for an apology for your personal insult rather than hiding behind deleting your original sarcastic response to my posting. Your kind of attack was supposedly the very essence of the rationale for changing the rules in the first place...if that was the real reason.

E-Stat

09-14-2004, 08:14 AM

I did not attack Mr. Risch on this thread.
These comments are not germaine to the discussion:

"That demonstration of my proof of his inconsistency and illogic should still be available in the archive should anyone care to find it and read it."

"Mr. Risch IMO has invented a new self serving illogical and inconsistent method for measuring non linear distortion which of course he immediately applies to justify his apology for the after market audio cable industry."

As for you, I'm still waiting for an apology for your personal insult rather than hiding behind deleting your original sarcastic response to my posting.
I edit many a post after reflection. And you're correct. I apologize as moderator for my first reaction to "Skeptic Speaks Out". I really need to bite my tongue first when the pomposity begins...

rw

skeptic

09-14-2004, 08:24 AM

E-Stat

09-14-2004, 08:49 AM

Just ask any fan of vacuum tube amplifiers where distortion typically runs from 0.5% to 2% or fans of vinyl phonograph records where distortion typically runs from 2% to 5%. They will tell you those levels are also inaudible. Whatever the listening attributes of vacuum tube amplifiers or vinyl phonograph records are, from a point of view of electrical performance specifically in regard to non linear distortion, by today's state of the art standards, they stink.
I would like to see a controlled listening test involving the bypassing of a preamp line stage with attenuators. As in completely removing the preamp from the signal path. The unit's design (SS, tubes, hybrid) is really not critical. Why a preamp's line stage? Because it is the only one that can be superfluous with some systems. Using a high output, low impedance source like some CDPs using low cap cables to eliminate HF rolloff effects, compare the presence of the line stage to its absence. Whatever small amount of measured distortion is present with the preamp should render the comparison identical -- at least in theory. Is it?

rw

skeptic

09-14-2004, 09:05 AM

The use of a so called "passive preamplifier" can cause serious degradation in overall system performance because in an "active preamplifier" the volume control sits between two gain stages which buffer the input and the output from the previous and succeeding stages and place the volume control potentiometer in a circuit which is specifically designed to minimize its audible effects except for a change in gain. There may be other minor frequency response changes created by some active preamplifiers which can be slightly audible but their signifigance is invariabley minimal except to those whose favorite expression is "it blew the other one away." Even vacuum tube preamplifiers if they are well designed have minimal distortion. Most audible nonlinear distortion from vacuum tube systems comes from the power output transformers whose nonlinear magnetic properties, even for the best designed units and the relatively high output impedence which reduces damping factor significantly thereby reducing the amplifier's ability to surpress spurious woofer resonances. Worse still are those whose lack of negative feedback increase non-linear distortion at least a full order of magnitude or the inexpert use of non linear feedback which can cause ringing.

FLZapped

09-14-2004, 09:11 AM

To know that non linear distortion levels of 0.1%, 0.01%, and 0.001

Or to put it anopther way, -40, -60 and -80dB respectively.

-Bruce

skeptic

09-14-2004, 09:14 AM

The calculations are simple to anyone who belongs in an electronics laboratory. To those who don't and wander in anyway, you can look but don't touch anything. What you don't know can kill you.

E-Stat

09-14-2004, 09:19 AM

The use of a so called "passive preamplifier" can...
I am aware of the theory and the potential issues. Which is why I qualified certain conditions. Can a 75 ohm output source comfortably drive an amplifier with a 137k ohm input resistance?

rw

FLZapped

09-14-2004, 09:20 AM

Interesting. I guess that is a sad commentary on cultural literacy today. They should have asked a second grader who would know the difference.

rw

While I agree with the literacy statement, that is not the point, because any other example could have been applied. The point being made is that it is exceptionally easy for people to dream up things that didn't happen and believe that they did. A fantasy.

-Bruce

J Risch

09-14-2004, 09:23 AM

Or to put it anopther way, -40, -60 and -80dB respectively.

-Bruce

Those levels of distortion represent -60, -80 and -100 dB respectively.

Well, you were only off by 20 dB, what's a few dB among friends?

Jon Risch

J Risch

09-14-2004, 09:29 AM

To know that non linear distortion levels of 0.1%, 0.01%, and 0.001 are not audible to human beings or that increases in distortion of these orders of magnitude are also inaudible doesn't take a research project into the history of auditory measurements.

I do believe that the higher orders of distortion, the 5th, and definitely the 7th and up, would be audible at 0.1%. However, that is still a moot point, and not what I was getting at.

Those numbers DO NOT have a ready correlation with the measured results from an audio device, for the very reason I just mentioned: we are more sensitive to the higher order distortion products. In many cases, we can not hear 1% 2nd harmonic, or a 2nd order type distortion, and THAT's why some tube amps sound better than they measure, they tend to have low order distortion, while SS amps with lot's of feedback tend to have lots of higher order distortions.

There is no simple metric, such as "less than 0.1% is inaudible", the papers aren't there, the correlation is not there. You can continue to ignore these aspects of audio, but sticking you head in the sand does not make the truth go away.

Jon Risch

skeptic

09-14-2004, 10:28 AM

jneutron

09-14-2004, 12:26 PM

I do believe that the higher orders of distortion, the 5th, and definitely the 7th and up, would be audible at 0.1%. However, that is still a moot point, and not what I was getting at.

Those numbers DO NOT have a ready correlation with the measured results from an audio device, for the very reason I just mentioned: we are more sensitive to the higher order distortion products. In many cases, we can not hear 1% 2nd harmonic, or a 2nd order type distortion, and THAT's why some tube amps sound better than they measure, they tend to have low order distortion, while SS amps with lot's of feedback tend to have lots of higher order distortions.

There is no simple metric, such as "less than 0.1% is inaudible", the papers aren't there, the correlation is not there. You can continue to ignore these aspects of audio, but sticking you head in the sand does not make the truth go away.

Jon Risch

Jon

Having little interest in the topic overall, I did not read your preprint..

1.. Did you correlate standard tests against yours?
2.. Did you do this using resistive loads or reactive loads, and to what power levels.
3.. Did you show distortion products that rise above accepted jnd's which otherwise did not?

Why has industry not adopted a test methodology that you claim is better?

Does your current employer, Peavey, use it? After all, you submitted it under their auspices..and I assume, they paid for it..

Or, are you alone in your beliefs.

Cheers, John

PS..."what's a few dB among friends?"

Now THAT was funny... (sorry Bruce)

jneutron

09-14-2004, 12:36 PM

In a thread John Curl published and which was quoted here a year or two ago, he boasted that he had some of the most sensitive distortion measuring equipment in the world and that the greatest difference he could measure between the best interconnect cables and the worst which were $1 Radio Shack was minus 135 db versus minus 120 db of the 7th harmonic of 5 khz. If there was even the slightest doubt in my mind that Radio Shack cables weren't as good as I could hear for an audio system, that dispelled the last of it.
As I recall, Curl eventually tempered his claims down to "the distortion products may correlate to some other as yet unknown phenomena", instead of claiming that the distortion levels were audible..

Although, I do not agree with him that the wires were actually causing it..I still believe it was a test equipment issue.

Wanna go backwards in time and argue digital jitter again and tell me one more time why digital jitter from audio cables is audible while digital jitter thousands of times greater from the spinning disc isn't?
I would personally love to see how a spinning low mass disk of plastic can have it's rotational velocity controlled to the extent that data is presented to the read laser at low jitter levels...levels which can be altered by a sandbag on the crystal..

Course, I think an argument can be presented to show how the electronics that read the data can alleviate the physical limitations of the disk motor..so I think, the actual question would be, does a 20 picosecond jitter do anything further down the line? And, could a sandbag do anything to that?..

But, I think the topic in this thread is the JR distortion signal and how it is stated as being better than everyting else..

I'd love to hear an explanation about how superposition does not apply to the electronics..

I'll even give a hint....silicon transient thermal behaviour has a time constant of 10 uSec at the die surface, about 100 uSec to die backside, and 10 mSec to the heatsink. and all of these thermal time constants are inaccessible by the outside world when the die is connected to electronics...I know, I have tested all those time constants..

And, I have this nagging concern that FFT's can't readily discern some of the distortion products..no facts, just a gut feel...and no, I haven't had any Thai food lately..

Welcome back....

Cheers, John

skeptic

09-14-2004, 03:51 PM

"As I recall, Curl eventually tempered his claims down to "the distortion products may correlate to some other as yet unknown phenomena"

Yes, the ghosts of dead aliens killed when their spacecraft crashed in the Nevada desert.

"I would personally love to see how a spinning low mass disk of plastic can have it's rotational velocity controlled to the extent that data is presented to the read laser at low jitter levels...levels which can be altered by a sandbag on the crystal..

Course, I think an argument can be presented to show how the electronics that read the data can alleviate the physical limitations of the disk motor..so I think, the actual question would be, does a 20 picosecond jitter do anything further down the line? And, could a sandbag do anything to that?.."

The obvious answer is that the digital jitter of the cable is insignificant especially in relation to the relatively enormous jitter of the rotating disc. The mere supposition that it matters goes to the heart of the lack of understanding of how bit stream technology works. The stream MUST be buffered, it MUST be reclocked, and the waveform MUST be regenerated by a Schmidt trigger or it won't work. If for any reason this scheme breaks down by say depleting the buffer registers, the entire process fails catastrophically. If it is momentary, you hear a characteristic click. Sustained and you get nothing. That is one of the many beauties of it. If it works properly, you can make a thousand generations of copies and the last generation will be indistinguishable from the first (no matter what digital cable you use.) The reason I brought it up is it was one of the more obvious blunders in Mr. Risch's last round of arguements he had with me several years ago. If he is right, I am saddened that it is no longer accessible. It was a classic debate.

There should be no doubt about the signifigance or importance of What Mr. Risch is asking us to accept. IF, and that's a very big IF, he is proven right, the entire method the audio industry uses to design and evaluate all of its products will change forever. Any scientist or engineer I ever met who would contemplate effecting such a revolutionary change would compose a very scholarly exposition of his theory and a demonstration of how it worked. He would answer a million questions and if he supplied the right answers, new test equipment would emerge, design engineers would go back to school, and evey piece of gear in every data base would be revisited to better understand it in light of the new knowledge. Did Mr. Risch do any of that? No, not this time and not in the past. He published it on a web site, it was written up in a consumer magazine, and is now being discussed on an internet chat board most of whose readers don't have the foggiest. Is that good enough? No, not for me, and not for other engineers and scientists. I hope Mr. Risch presents his paper. Then it will get the trial by fire all such proposals are subjected to. I'm sure it will be subjected to far more critical scrutiny than anything I could ever dream up.

J Risch

09-14-2004, 03:56 PM

Interesting, trying to use IM as HD, and blame me for your confusion. Right.

If you would bother to re-read your reply, it is you who started going off on IM, when I was talking about HD. Not my confusion here. (the format I see when reading and posting here does not lend itself to reading a coherent thread of posts and replies, argh!)

What you described by any standard is IM distortion. Not Harmonic distortion. By world-wide recognized standards, harmonic distortion is measured with a single tone and is supported mathmatically. Intermodulaton is measured with multiple tones. These are given definitions that the rest of the engineering world recognizes as a standard, except you, apparently.

Bruce, I will use a very simple and straight-forward example, perhaps this will register.

In a previous comment, I mentioned that one could gather harmionic distortion data from a test signal with more than one tone, using the classic IM test signal pairs as an example. Now I will step through it, and I want you to then tell me specifically how what I have said is wrong, or untrue, or can not be done.
If we examine the classic SMPTE IM signal, it consists of a 60 Hz tone, and a 7 kHz tone. Now if we tried to use the old style measurement equipment, that used filtering to remove the 60 Hz component, and then looked at the amount of 7 kHz modulation, or the side bands, you would not be able to discern anything but what the machine was designed for, it is hard wired to do one thing (perhaps similar to your brain? ;-) )

But we can take that same SMPTE signal, and run it into an FFT spectrum analyzer, and see all possible distortion components that might get generated. If we looked at the IM signal source directly into the analyzer, and the source was clean, then all we would see is 60 Hz, and 7 kHz. However, once we run that through an audio device under test, which has some distortion, and feed that into the spectrum analyzer, we will now see ALL the distortion products that were generated, INCLUDING any harmonics.

There would be the IM distortion products at 7060 Hz, and at 6940 Hz, as well as the 3rd order products at 7120 Hz and 6880 Hz. However, that is not all that will likely be present.
There will also be harmonic distortion products at 120 Hz and 180 Hz, as well as 14 kHz, and 21 kHz. These will be clearly displayed on the spectrum analyzer, and can be measured relative to the level of the fundamentals, and the amount of HD calculated.

Thus, what is normally considered to be an IM test signal, with two tones, can also be used to check for harmonic distortion (but only at those two primary tone frequencies, we still don't know what kind of HD will occur at other frequencies, say, in the midband at 1 kHz). Your statement that "1) You can ONLY merasure harmonic distortion with a sing le tone" is not correct, and has been shown to be false.

My Phi Spectral multitone test signal is an extension of this same technique, only it uses either 6, or 10 or 12 tones, all of which are spaced so as to avoid any significant cover-up of one particular distortion product by another. That is the big deal with my test signal, it avoids the common error commited by ALL the other multitone test signals that went before. Not only that, but because each distortion product has a unique frequency, you can determine which tones (or a tone and another distortion product) were responsible for it, again, something that you could not do with the other commonly available multitone test signals that were available then. The AP FASTTEST signal is a good exaple, with primary tones at 1/3 octave intervals, you can not see hardly ANY of the HD products, OR any of the IM products, they are all going to end up landing right where there is already another primary tone, effectively rendering them invisible.

Devices are either linear, or they are not. Either they produce distortion products, or they don't.
The physics don't change with the operating frequency.

Actually, they do change with frequency in audio devices, that is exacty what I have been trying to tell you! It is very common for audio devices to have a lower level of HD in the midband, and then have much higher levels at the frequency extremes, say at 100 Hz and at 10 kHz. There are thermal considerations, biasing and operating points that changes with level and frequency, etc. so you CAN NOT make the same kind of prediction that you can with RF amps. This is not someting that any audio engineer or tech would need citations or references for, it is common knowledge, but if one really were that much in the dark, all you would ahve to do is look at some of the Stereophile test reports that are available online, and see that HD levels change with frequency.

Again, you think the physics change? Did you miss the fact that your engineering text book doesn't have a seperate section on defining harmonic and intermodulation distortion for audio vs rf?

Please, get real, the engineering textbooks do not call out every conceivable real world situation, and the whole idea of going to school was to learn to THINK, not regurtigate the text books. The data is out there, audio amps, and other audio devices have HD and IM that vary with level, with frequency, even vary with the past signal history of the device!!!

Yet you think it is okay for you to espouse several different laws of physics as to how IM and harmonic distortion are generated at audio vs rf. Yet you say we are violating the laws of physics? I have yet to see you show anywhere which ones are actually being violated. You're just hand waving.

I am not the one hand waving here, or sticking to a very narrow and outdated view of how one can measure audio equipment.

Enough of this squirming around to deflect the real purpose of this discussion:

Your multi-tone test signal is completely unusable to measure intermodulation distortion and is a violation of the recognized definition in measuring harmonic distortion.

Two tones, are all that's needed for IM. Regardless of operating frequency.

Harmonic distortion is measured using a single tone, regardless of operating frequency.

This is recognized world-wide and has been so for a long, long time and no one has proven otherwise. Including you.

My Phi Spectral test signal is not unusable to measure HD or IM, in fact, it is superior to the classic one tone HD and two tone IM tests, in that it streses the DUT with multiple tones, more like real music.

Two tones for IM ONLY show us what the DUT is doing WITH THOSE TWO FREQUENCIES and not for anything else.

HD can be neasured using more than one tone, as I have shown above, and can be measured using the proper type of multitone signal, one that avoids distortion product cover-up, such as my Phi Spectral multitone.

Even your test signal follows these laws. The problem is, your test signal will generate SO many products it would be impossible to distinguish noise from distortion products making it unusable as a viable test signal.

This is just not so, and as I have stated before, and spelled out in the paper, with the aid of a spreadsheet (or a computer program that ca generate all the possible distortion combinations and the resulting frequencies) that shows the various combinations possible, one can determine exactly where a given HD or IM product came from, or at what frequency an HD or IM product will appear. Since they do not cover one another up, they can be individually distinguished.
Yes, IF the S/N ratio of the DUT is so poor, that the noise is high and at similar levels to the distoriton products, then we will not be able to see or detect the distortion for the noise, BUT THIS IS TRUE FOR _ANY_ TEST SIGNAL, INCLUDING THE CLASSIC ONES YOU KEEP HARPING ON.

If you refuse to think, and refuse to consider anything other than what you already 'know',. then there is no point in discussing this further, and I think that other people will be able to see my points clearly, and draw there own conclusions.

Jon Risch

E-Stat

09-14-2004, 04:23 PM

(the format I see when reading and posting here does not lend itself to reading a coherent thread of posts and replies, argh!)
There is a solution to the default "linear mode" thread presentation. Scroll near the bottom and look to left for the display options. You can return to the original style or choose the middleground hybrid.

rw

J Risch

09-14-2004, 05:11 PM

Having little interest in the topic overall, I did not read your preprint.

That begs the question: why so many questions now? At least yours make some sense.

You really should read the paper, I have the text at:
http://www.geocities.com/jonrisch/PhiSpectral1.htm
be sure to click all three pages worth.

1.. Did you correlate standard tests against yours?

I did to a limited extent, using primarily loudspeakers, plotting 2nd and 3rd harmonic against the Phi Spectrals. I had two comparisions in my paper, but one of the graphics got left out (I handed out the mising sheet at the convention for those who attended)

2.. Did you do this using resistive loads or reactive loads, and to what power levels.

Real loudspeakers. If you meant for power amps, I did not do extensive testing of power amps as a separate category, but since the paper, I have measured a few more, and the big thing is, doing so at different power levels.

3.. Did you show distortion products that rise above accepted jnd's which otherwise did not?

I did show distortion levels that exceeded the simple IM or classic HD plots by 10-12 dB, however, some folks would have argued that some of the HD levels were already above audibility, however, I was able to show that a speaker tha measured "OK" by HD metrics, measured much worse using the Phi Spectrals, while another speaker that measured similarly to the first one on HD, remained low on the Phi Spectral. This was one of my points of evidence for the superior resolving power of the Phi Spectral.

Why has industry not adopted a test methodology that you claim is better?

The industry is all over the map, the current simple and limited measurements we have today evolved over a period of many years, and it took years and years for the industry to agree on some of those standards. I do believe that it took almost 10 years for the SMPTE IM standard to be offically adopted, and look how simple that is!

I can say that Klipsch and Cerwin-Vega are using it, or have used it at one time, there may be more than that, most folks would NOT advertise they were using such a powerful tool, if they felt that by keeping under the radar, they would keep other folks from noticing and using it too.

Does your current employer, Peavey, use it? After all, you submitted it under their auspices..and I assume, they paid for it..
Or, are you alone in your beliefs.

I can't really comment on that specifically, suffice it to say, that we could not have developed a 4" format compression driver to have distortion as low or lower than a TAD driver, at about 1/4 the cost, just by accident.
I can also say that I work with many groups within Peavey, including the power amp folks, the guitar folks, and even at times, the digital engineering guys. I can not go any further than that.

BTW, ALL of the time I spent on developing and researching the Phi Spectral was on my own time, after hours or at home. I even paid my own way to the AES convention, which is another story, and one I am also not at liberty to discuss.

For the future:
I have been working with some folks on a super version of this, one that will be wholly integrated into a computer controlled environment, so that much of the analysis would be automated and made easy to view and interpret, as well as a VERY neat twist that will make it even more powerful and relevant to measuring audio devices! This may take a bit of time though, as we are talking about some other guys working in THEIR spare time.
Should be a very interesting end result, if we can get it to do what I think it can.

Jon Risch

J Risch

09-14-2004, 08:51 PM

The obvious answer is that the digital jitter of the cable is insignificant especially in relation to the relatively enormous jitter of the rotating disc. The mere supposition that it matters goes to the heart of the lack of understanding of how bit stream technology works. The stream MUST be buffered, it MUST be reclocked, and the waveform MUST be regenerated by a Schmidt trigger or it won't work. If for any reason this scheme breaks down by say depleting the buffer registers, the entire process fails catastrophically.
This is, of course, a diversion from the main topic, which you seem to know very little about. However, to set the record straight (since the old posts are not really there anymore), I am compelled to correct your misinformation.

Of course there is buffering, there is reclocking, there is crystal control IN SOME CASES (but not all), but that was not the crux of the matter as far as the use of a separate transport and DAC are concerned.

As I spell out at this page:
http://www.geocities.com/jonrisch/jitter.htm

all of these actions you describe, the reading of the data, the buffering, the reclocking, the reshaping, all of them affect the power supply, cause transient drains on the PS rails (and cause ground bounce as well) that occur more or less in time with the activity that is going on, and at the basic clock rate (and submultiples) within the player. There are also drains and transients that are not at the clock rate or submultiples, these would be the analog output stage itself, the read servo and motor speed circuit, etc. The result of all of this activity impinging on the PS is that the device that actually converts the digital data into an analog signal, the DAC, is being presented with a PS rail and ground that have a sing song related to the digital signal activity, that is related to the servo activity, that is related to the motor speed adjustment activity, etc. and all of these things are going to introduce timing errors into the conversion within the DAC. Timing errors known as jitter.

(As noted at my page, even if the DAC were presented with a perfect PS and ground, it is still subject to internal LIM.)

So even with buffering, recloking, reshaping, YOU CAN'T GET AWAY FROM THE PS MODULATION.

Now all of this occurs within ANY CDP, not just a transport and DAC combo, but when we look at a transport/DAC combo, we find that there have been added to this PS sing-song, additional PS transients due to the presence of the SP/DIF output, and due to the receiver circuity, and additional jitter due to the finite bandwidth of the cable (and of the digital output/input circuits as well) and the less than perfect noise and interference rejection of the cable and receiver.

Those things that you were talking about before? The buffering? The reclocking? The reshaping? Those all tend to reduce the raw jitter coming off the disc down to levels that are now limited more by the PS sing-song that is going on, than the raw disc variations.
Once we introduce a digital IC between a transport with it's digital output, and a DAC, with it's receiver circuit, we have ADDED to this PS sing-song as well as introduced additional jitter directly due to the cable and transceiver bandwidth limitations, and THIS is why a digital cable can have the effect it does.

The reason I brought it up is it was one of the more obvious blunders in Mr. Risch's last round of arguements he had with me several years ago.
In your dreams again. I suppose you would see it that way, but not too many others did (the usual naysayers were cheering you on, but they didn't really know what was going on in the first place).

There should be no doubt about the signifigance or importance of What Mr. Risch is asking us to accept. IF, and that's a very big IF, he is proven right, the entire method the audio industry uses to design and evaluate all of its products will change forever.
Indeed. And some of us are using it already. :-)

Any scientist or engineer I ever met who would contemplate effecting such a revolutionary change would compose a very scholarly exposition of his theory and a demonstration of how it worked. He would answer a million questions and if he supplied the right answers, new test equipment would emerge, design engineers would go back to school, and evey piece of gear in every data base would be revisited to better understand it in light of the new knowledge. Did Mr. Risch do any of that? No, not this time and not in the past. He published it on a web site, it was written up in a consumer magazine, and is now being discussed on an internet chat board most of whose readers don't have the foggiest. Is that good enough? No, not for me, and not for other engineers and scientists. I hope Mr. Risch presents his paper.

I did present it, at the 105th Convention of the Audio Engineering Society
in September of 1998, in San Francisco, CA as preprint #4803.
I presented to a packed hall, and was asked a lot of questions, but with the usual scene at the conventions of things running late, I was asked to take the bulk of the questions out in the hall, where I distributed approx. 30 CD-R's containing tracks with the multitone signal on it, and diskettes with the spreadsheet. I collected approx. 27 bussiness cards for those who still desired a set of discs, and mailed those out at my cost, to those people.

Since that presentation, I have gone through two batchs of paper hardcopy preprints, not counting the numerous electronic copies I have sent out at request.

A. Voishvillo of Cerwin Vega has cited my paper in his work on multitones, and as I said in the opening post here, people from all over the world have expressed interest, and asked for a copy, or asked questions about the paper, or asked questions about different versions of the Phi Spectral multitone.

My presentation at my web site, and at this forum, are complementary, and in addition to the one at the AES..

Jon Risch

ToddB

09-15-2004, 03:09 AM

This is going to read as if I'm replying to Jon, but it applies to the thread in general.

Yes, let's keep this on topic. If there are other issues that people would like to discuss, please start other threads about them.

Also, I think all of us (myself included) can probably tone down the personal invective. For the most part, I think this exchange has gone amazingly well, and it's been very interesting and informative, and I for one would really like to keep it that way.

I don't have any particular technical knowledge or experience related to this subject, so take my opinion for what it's worth, but based on the arguments given in this thread, I'm not seeing a sufficient rationale for taking the position that Jon's test method is without merit. The argument that his new method somehow suggests that the previous methods are wrong seems to be particularly flawed, since scientific advancement historically doesn't seem to be so much about disproving previous understanding, as it is about providing more clarification and refinement of previous understanding. Unless one holds the position that the current methods and abilities of distortion measurement are inclusive of all relevant aspects, and will forever continue to be so, then I think common sense suggests that methods of acquiring more data would be beneficial, IF that data can prove to bear out some experiential corellation, as Jon suggests his method indeed does.

Also, and perhaps this is more significant, nobody seems to be disputing the validity of the actual test method itself, nor the figures Jon claims to have generated by using it. And I don't believe that anybody said a thing about Jon's claim that using his method enabled him to discover problems with the digital filters in some of the CD players he tested. That purpose alone would seem to be an eminently useful aspect of his method, even if it's potential elsewhere remains in dispute.

I think someone asked if I was "pretending"(?) about wanting people's opinions about this subject. I was not. What piqued my interest in this was reading a review of some Simaudio component, and the reviewer stated that the product literature mentioned that Simaudio try to eliminate IM from their products, because they think it's more detrimental to sound quality than HD. Jon has a test method for measuring these that's different than any I'd read about anywhere else, so, here we are.

Jon, I'd appreciate it if you could elaborate on what you meant about the "past signal history" portion of this statement:

The data is out there, audio amps, and other audio devices have HD and IM that vary with level, with frequency, even vary with the past signal history of the device!!!

That's a new one for me.

skeptic

09-15-2004, 04:55 AM

"I don't have any particular technical knowledge or experience related to this subject"

You are correct. Technically, you are way out beyond your depth. You don't have even the slightest understanding of what this debate is really about. It's about overturning hundreds of years of mathematics and nearly a century of electrical measurement science. If it's true, it's genius. If it isn't, it's worthless trash.

skeptic

09-15-2004, 06:10 AM

"A. Voishvillo of Cerwin Vega has cited my paper in his work on multitones"

So far an army of two? Well at least it's a start. How ironic that one of your first supporters should come from a company whose products' only redeeming virtue as I see it is that they allow music haters to become permanently and profoundly deaf at the lowest possible cost. :-)

jneutron

09-15-2004, 06:22 AM

That begs the question: why so many questions now?
Umm, well...because there are 65 posts on the topic, just before mine..and parts of the discussion have tweaked my interest..

I can also say that I work with many groups within Peavey, including the power amp folks, the guitar folks, and even at times, the digital engineering guys. I can not go any further than that.
A simple yes or no would have sufficed, as you are working for a company which derives profits from their work..I cannot expect IP to be divulged.

Although I work for the DOE and am required to publish what I do on our web pages, in publications, at conferences, and in seminars, not all of it is revealed..we tend to gloss over the high falutin stuff, and present lower level synopsis' of techniques and analysis for the scientific and engineering communities, so that they can understand what the end product is and how difficult it is to get there...

Cheers, John

FLZapped

09-15-2004, 06:35 AM

Those levels of distortion represent -60, -80 and -100 dB respectively.

Well, you were only off by 20 dB, what's a few dB among friends?

Jon Risch

You are correct. I missed thinking about 10% being the first step and jumped to 1%. My bad.

-Bruce

FLZapped

09-15-2004, 06:48 AM

Bruce, I will use a very simple and straight-forward example, perhaps this will register.

My, my, look how quickly the ad hominem attacks begin. hardly out of the first paragraph.

Actually, they do change with frequency in audio devices, that is exacty what I have been trying to tell you! It is very common for audio devices to have a lower level of HD in the midband, and then have much higher levels at the frequency extremes, say at 100 Hz and at 10 kHz. There are thermal considerations, biasing and operating points that changes with level and frequency, etc. so you CAN NOT make the same kind of prediction that you can with RF amps. This is not someting that any audio engineer or tech would need citations or references for, it is common knowledge, but if one really were that much in the dark, all you would ahve to do is look at some of the Stereophile test reports that are available online, and see that HD levels change with frequency.

That has nothing to do with the basic physics involved. The products are still there as predicted.

My Phi Spectral test signal is not unusable to measure HD or IM,

It is completely unusable to make meaningful measurements. As you said, it would take a massive spredsheet to sort out all the possible combinations especially when you include multiple order products. The results would be indistinguishable from noise.

in fact, it is superior to the classic one tone HD and two tone IM tests, in that it streses the DUT with multiple tones, more like real music.

That's what we have pink noise for. Again, a world-wide recognized standard.

The rest I have already covered.

-Bruce

ToddB

09-15-2004, 03:14 PM

You are correct. Technically, you are way out beyond your depth. You don't have even the slightest understanding of what this debate is really about..

Which of course has absolutely no bearing on my intelligence or deductive reasoning abilities for the purposes of this thread. Really, the posturing and hyperbole are not helping your argument.

It's about overturning hundreds of years of mathematics and nearly a century of electrical measurement science.

I don't see that it does any such thing. Jon clearly based his new test method on the already-existing methodology, which would make his version simply an evolution and refinement of the previous approach, much like the way progress in other scientific fields has occurred.

If it's true, it's genius. If it isn't, it's worthless trash.

And history is replete with people who thought outside the box of conventional scientific wisdom, were reviled at the time for doing so, and were later proven to have been correct. Although I don't have the technical wherewithal to evaluate Jon's data, you and others apparently do, but instead of giving it an honest scientific evaluation, I'm seeing a response that seems to be mostly predicated on non-scientific and decidedly human considerations. Sometimes the apple cart gets upset, that's just the way life goes.

ToddB

09-15-2004, 03:23 PM

It is completely unusable to make meaningful measurements. As you said, it would take a massive spredsheet to sort out all the possible combinations especially when you include multiple order products. The results would be indistinguishable from noise.

This I'm still not clear on. If it's necessary to obtain results out to the nth degree for the method to have any usefulness, how do you explain the results Jon did obtain, since he presumably did not do that? Certainly limiting the calculations to some established threshold would make them easier to interpret, but would doing that also automatically invalidate the results?

skeptic

09-15-2004, 03:52 PM

"Which of course has absolutely no bearing on my intelligence or deductive reasoning abilities for the purposes of this thread."

True but it does bear on the knowledge you have to understand the crux of the debate. Were you to apply your intellegence and powers of deductive reasoning to study the applicable science and underlying mathematics, it is entirely possible that you could acquire that knowledge. Unfortunately that takes many years in an engineering school, not minutes or hours on the internet.

"I don't see that it does any such thing."

As I said, you don't understand the implications of the issues at the heart of this debate. If what Mr. Risch says is correct, either the entire mathematical analysis by Laplace and Fourier which completely characterizes both periodic and non periodic waveforms is wrong, or all of the work done by PHDs in electrical engineering and mathematics to develop the instrumentation to precisely make the measurements don't reflect the mathematics they are based on.

You can characterize my comments as hyperbole or posturing if you like but the sharpest criticisms I can level will be as nothing compared to what this theory will face by the huge corporations like HP who manufacture the worlds finest instrumentation and who will defend their technology and the underlying science behind it. Guess who I'm putting my money on.

"Jon clearly based his new test method on the already-existing methodology, which would make his version simply an evolution and refinement of the previous approach"

No! He claims the present method is inadequate and gives false results. He postulates that it disguises the true answers. At the very least, he will have to show that nonlinearities in the existing equipment or random noise disguise the actual results using the present method and that his doesn't. This is a very steep uphill climb. He will face the people who have designed and tested this equipment. Unless you've worked in industry, you have no concept of how hard manufacturers work to tear down their own products to find out exactly what the limits of their capabilities are.

"And history is replete with people who thought outside the box of conventional scientific wisdom, were reviled at the time for doing so, and were later proven to have been correct. "

It's also far more replete with crackpots who could impress the rabble in the streets but were proven no more than charlatans. I'll believe he's the second coming when I see in the paper that he walks on water.

RobotCzar

09-15-2004, 04:22 PM

I really do try to put myself in your shoes when I read comments like that. You relate from a completely different, detached point of view. You know what you've read. I know what I have experienced.

rw

I will soon not post here at all. But, I will take the time to try to make a couple of points to you:

1. When you are cornered about some assertions you make (e.g., "simple" test signals are inadequte to judge amp performance) you resort to talking about what you experience. That is not fair. Are you always talking only about your experience or are you making wider claims (objective claims) about amp distortion and audibilitiy? You really shouldn't move back and forth between facts and experiences. The point I made above is that it is scientifically and mathematically valid to test amps with pure tone sine waves. That statement is contrary to what many high end audiophiles say and they are simply wrong about it because they are using their intuition and "common sense" which happens to be dead wrong. And, if they are wrong about something as basic as this (like Jon R. is) then why should they be given credibility about other electronic and audio issues?

2. If you really are only comming from the view of your experiences, then that is of very limited use to the rest of us, because we are not you. That is the essence of being "subjective". Many of us who support a more rational approach do not deny that you preceive what you claim to percieve, we just doubt the REASONS for that perception. For example, perception is known to be greatly influenced by expectation. Therefore you might really perceive a difference in the sound of a component you expect to sound better (perhaps because it is more expensive). The standard way to protect against such a bias in scientific testing is to prevent you from "knowing" which component is the more expensive (this is called blinding). In that case your expectations cannot influence your perception.

I can't help it that many many people have claimed to easily hear amp differences (like you do) but have failed to demonstrate that they can when they have nothing to hang their expectations on (i.e., they are blinded). But, that is pretty much what has always happended when audiophiles claiming to hear differences in low distortion amps have been tested (to my knowledge). it would be very illogical for me to assume that your experience is due to amp differences when you haven't taken the time to test yourself by taking the proper precautions to eliminate known reasons for people to 'experience" audible differences (e.g., level matching).

I have merely tried to point out that your explanations (which are for the most part straight "party-line" explanations offered by high enders) are contrary to fact, logic, and evidence. I don''t doubt your experience, only your explanations of your experience.

FLZapped

09-15-2004, 04:40 PM

This I'm still not clear on. If it's necessary to obtain results out to the nth degree for the method to have any usefulness, how do you explain the results Jon did obtain, since he presumably did not do that? Certainly limiting the calculations to some established threshold would make them easier to interpret, but would doing that also automatically invalidate the results?

What Jon claims he did and what Jon can actually produce are two different things. If you had the history with him that many of us do, you would immediately know this without explaination. :)

I didn't say the results are invalid, just unusable. Like that old quip: "Too many cooks spoil the broth" - too many test tones spoil the test.

One other thing you have to understand is that these tests must be able to be performed outside the engineering lab. Make it too complicated makes it unusable anywhere but the engineering lab. Okay, so how is a tehnician out in the field going to be able to relate his findings to an engineer if they aren't speaking the same "test language" because he cannot perform this test and be able to interpret the results?

-Bruce

J Risch

09-15-2004, 06:35 PM

No! He claims the present method is inadequate and gives false results. He postulates that it disguises the true answers. At the very least, he will have to show that nonlinearities in the existing equipment or random noise disguise the actual results using the present method and that his doesn't.

You are not being clear here. Which present method?

If you are talking about single tone HD measurements, this is wrong because a single frequency measurement DOES NOT FULLY CHARACTERIZE THE DUT AT ANY OTHER FREQUENCY. I know that this is not so much the case for RF amps, which operate over a very small % octave basis, but for an audio power amp, which operates over a three PLUS decade range, or over ten octaves, it is indeed the case. This information is in the literature, and has been provided by many a power amp or preamp review. A simple linear equation, such as is used to determine the X order intercept point FAILS with most audio devices.

If you are talking about the prior multitones that were being used by others before I came up with the Phi Spectral multitone, then they were guilty of either a lot of distortion product cover up, or were gulity of a HUGE amount of distortion proiduct cover up (ala the AP FASTTEST signal).

When I state that the traditional single tone HD measurement is not going to be relevant for most audio devices, I am not trying to repeal Fourier or rewrite Laplace, not at all, I am simply looking at the inherent limitations of the existing signals that are currently used.
A single tone HD measurement all by itself does not provide the correct HD information for other frequencies that are far removed from the measurement frequency. A single 1 kHz HD measurement will NOT tell you what the HD is at 100 Hz or 10 kHz, for audio devices, it just isn't so.
When I say that the classic two tone IM signals do not excercise the entire audio spectrum, this is a completely true statement. Measurements taken with the three major classic IM methods will all DIFFER in the levels of distortion they record when used with audio devices. Doesn't this tell you something? It DOES invalidate FLZapped's comments, and renders your sweeping claims that I am trying to repudiate Laplace and Fourier as over the top and irrelevant to the issues at hand.

Jon Risch

J Risch

09-15-2004, 07:44 PM

What Jon claims he did and what Jon can actually produce are two different things. If you had the history with him that many of us do, you would immediately know this without explaination. :)
Totally irellevant to the technical discussion, and quite untrue as well.

I didn't say the results are invalid, just unusable. Like that old quip: "Too many cooks spoil the broth" - too many test tones spoil the test.

Two things. It is entirely one thing to say it is unusable, and another to say it is difficult to use, or that it is not the same as what I am used to doing. You are saying it is unusable, and this is not true. Is it not like what you are used to? Yes. Is it difficult for an inexperienced person to interpret? Yes. That does not invalidate the power it has, or the capability when used by competent people.

The second thing is, that by merely LOOKING at the FFT spectrum analysis result, one can SEE how high the levels of the distortion producs are. If you are concerned about the noise floor levels, then run an FFT analysis with a -110 dbFS signal level coming off the CD-R. This is the baseline for that particular combination of gear and measurement set-up. (This avoids the automatic muting that some CDPs have built in when they encounter enough samples of digital "zero input" in a row.)

In my case, I was able to regularly achieve a noise floor where none of the noise/distortion components was above approx. -105 dB from the nominal reference level. The multitone signal had pure tone components that were at -16.5, -21, or -22.5 (for 6, 10 or 12 tones respectively). So even the 12 tone Phi Spectral signal had a dynamic measurement range of over 82 dB. I could be fairly certain that ANYTHING that was registering at a level above -105 dB was a distortion product, and to check, all I had to do was cursor the frequency, and look at my spreadsheet.

An inspection of the measurement graphics from my paper would show that in most all cases, when stimulated with the Phi Spectral multitone signal, DUT's had SOME distortion products at levels well above -105 dB.

For the loudspeaker measurements, I even showed the noise floor due to the acoustic element as a greyed in set of data on the spectral plots, it can easily be seen that the distortion signals were well above this noise floor, and ALL of the spectral content above this floor was indeed distortion. So just by LOOKING at the plots of one DUT against another, it was immediately obvious that one had 6 or 10 dB of broadband low level distortion than another. As a concrete example that all can go look at, see Fig Y, at:
http://www.geocities.com/jonrisch/page10.htm

This shows one of the Phi Spectral test signals (not the only one) coming out of the reference CDP coming off a CD-R, and straight into the spectrum analyzer thru the usual signal path (included a known clean mixer to set levels).

Note the level of the primary tones, at a visible level of approx. -22 dB, while the noise floor (and/or residual CDP distortion) was at less than -105 dB, except for a little 60 Hz hum component at -100 dB. When I the tested another CDP, I found that I would see distortion products at -95 dB, a full 10 dB higher (this was Fig. 22 in my paper, vs Fig. 20). Of course, the noise level of the unit in Fig. 22 was checked, and it was approx. at the level of the spectral content in Fig. 20 (or comparable to my website Fig Y). This is a very simple way of looking at the overall audio band distortion content of one DUT vs. another.
Oh, BTW, more level in between the primary tones is BAD, less is GOOD.

One other thing you have to understand is that these tests must be able to be performed outside the engineering lab. Make it too complicated makes it unusable anywhere but the engineering lab. Okay, so how is a tehnician out in the field going to be able to relate his findings to an engineer if they aren't speaking the same "test language" because he cannot perform this test and be able to interpret the results?

This seems to say that if it is to difficult, it should not be tried or used. Why limit the cut-off to a tech? Why not say Joe Sixpak should be able to read the results? In point of fact, the modern test instruments we have can do this, push a button, and you get a THD read out. But we have found that this simple number is just not enough information, and does not directly correlate with what we hear.

Tube amps with a THD number of 2% sound MUCH better and more lifelike than a SS amp with a THD number of 0.008%. Or a more palatable comparison, the modern SS amp of 0.1% THD sounding better than the SS amp with 0.01% THD. These simple one dimensional metrics are highly flawed, and do not give us the ability to judge strictly by the numbers what amp will sound better, more lifelike and realistic to us.

In terms of what it takes to perform such a Phi Spectral multitone measurement, this does not exactly require a rocket scientist to do. As I outline in my paper, I used a digital based tone generation program (in my case, Cool Edit), created the test signals one pure tone at a time, mix pasted them together at the proper levels, burned the test signal to CD-R, and found out which CDP would play it back with a sufficiently low distortion level to use as the test signal source. What about the spectrum analyzer? With modern computer sound card based software and shareware, and a studio grade sound card costing less than $200, anyone can generate and spectrum analyze an audio device with a Phi Spectral multitone.

With a suitabkle full duplex soundcard, ne could simultaneously generate the test signal without the intervention of the CDP, and then take the signal in fromthe DUT and record it for later analysis using any one of a number of software programs. There exist a few such soundcard based software packages that can actually generate a multitone, and then analyze it nearly real-time.

These low cost and relatively simple test set-ups may be why some of the major names in measurement are not that interested in making the Phi Spectral available: it would literally wipe up their expensive hardwired dedicated equipment, and make it hard to for them to sell it at a huge profit. AP is not exactly going to shoot their FASTTEST and put it out to pasture, they have too much investment in it, even the TM and such make it their own special proprietary signal, which they have been marketing for years now. NIH is alive and well, and actively upheld at many companies.

I agree that it would be a good thing to make it easier to interpret and to share the data garnered from such a Phi Spectral multitone test, rather than be limited for conveniences sake to an A/B measurement comparison graphic (though this would still be a huge step forward in determining the performance of an audio device when stressed with more than just a single or pair of tones).
But that still does not mean that you can not calculate the THD, or the total IM distortion, or the total distortion by including all the relevant distortion products above a certain level, or even taking the distortion product data, and weighting the various products according to their order (7th order weighted higher than 2nd order by X amount, etc.). Given that this is a relatively trivial excercise to do on a modern computer based measurement system, it is not just a pipe dream or an impossibility as you seem to insist it is Bruce.

The Phi Spectral has already been used successfully to measure and compare various audio devices, and has turned up some interesting data in it's own right, such as the discovery of CDP digital filter clipping, and how much it differs from brand to brand, part number to part number. For you to continue to deny it has any usefulness or validity in the face of this, and of my explainations, defies reason and logic.

Jon Risch

E-Stat

09-16-2004, 05:05 AM

I can't help it that many many people have claimed to easily hear amp differences (like you do) but have failed to demonstrate that they can when they have nothing to hang their expectations on (i.e., they are blinded). But, that is pretty much what has always happended when audiophiles claiming to hear differences in low distortion amps have been tested (to my knowledge).
I think it was Mtry who finally produced a lone story of some audio dealer in Florida who was unable to hear the difference between a Yamaha integrated and his Krell amp, if memory serves. That is the only report I've seen on this board to back your assertion. If such other proof exists, I'd be curious to read it. When pressed, he admitted that he could not find any citations that include the kind of equipment that is available today.

I have merely tried to point out that your explanations (which are for the most part straight "party-line" explanations offered by high enders) are contrary to fact, logic, and evidence. I don''t doubt your experience, only your explanations of your experience.
"Fact" has yet to be established from my standpoint. See above.

You are correct in saying that I cannot explain the reason behind audible differences among a range of components once you eliminate basic variables such as loading, major frequency response variations, etc. It is also true that when you ask ten audio engineers that same question, you will get ten different interpretations. I am not referring to guys who design two-way radios, power distribution systems, telephone systems, etc. These are engineers who live and breathe audio reproduction, many of whom having been doing so for decades. That "science" has irrefutably found the answer completely ignores the reality of the audio market. If such were true, why doesn't some well financed company simply produce these allegedly "perfect" inexpensive killer components and put everyone out of business?

I will also agree that any subjective opinion of musical reproduction naturally involves a set of priorities established by that listener. For that matter, my priorities have changed over time. My overall posture is to encourage folks to hear a range of components to get a feel for the variations found. While I have no conceptual problem with blind testing, I do object to blind acceptance of "truths" set forward by some engineers who claim to have found the holy grail. Just like when they did in the early solid state era chasing low THD numbers. Do you acknowledge that there are many companies whose products of today measure worse than their counterparts from twenty and thirty years ago? Who do companies ranging from Crown to Pass Labs (formerly Threshold) find that chasing the single THD metric was futile and not beneficial to providing the best musical reproduction? Just like when they did in the early 80s when CDs emerged. Perfect sound forever? It was those "wascally" audiophiles who immediately pointed out "hey guys, something isn't right here". Twenty some years later, we have a greatly improved product. On that topic, I hear conflicting defenses to that observation. On the one hand, you have those who claim that there have been absolutely no advances in basic circuit design and thus audible fidelity for decades. On the other hand, others posit that the early CD engineers knew of the limitations but simply didn't have the technology at the time. Go figure. RBCD is still not "perfect" IMHO. I do not accept the notion that "the only reason behind the high resolution formats is for strictly marketing reasons".

You continue to harp on the "if it's more expensive, it must be better" notion. Many times that is the case, many times it is not. On two different listening situations, I heard differences between CDPs and power cables for which I was rooting for the underdog. Objectively, however, I evaluated their performance for what it is - or what it was not. BTW, I ended up purchasing the "loser" in the CDP comparison and am quite pleased with that purchase of three years ago.

In the final evaluation, it is the continuous process of questioning our realm of known science that betters the technology. We all benefit. I'm sure glad that we're not stuck with those dreadful early sixties SS amplifiers today, despite their "better" measurable performance.

rw

skeptic

09-16-2004, 05:50 AM

I'll grant you this much, at least you no longer present us with 10 page postings with countless hot link references to endless other papers, articles, and whatever the way you used to. Trying to get through even one of your old postings was only slightly more tedious than reading War and Peace from cover to cover. I admit I never actually got all the way through even one and eventually I gave up trying.

My problems with your theories will be as nothing compared to the cross-examination you will face from people who are actually expert in this field. I am merely a hobbyist with a long time ago bachelor degree level education in electrical engineering. That's nothing compared to what you will have to deal with at the highest professional levels. Statements like "The correlation between which unit sounded good, and which didn't followed the Phi Spectral measurements almost exactly." will get you laughed out of the arena assuming they ever even let you in. Considering you have lost every prior debate over cables you've had with "just lil ole me" through simple logic, you'll have to be a lot more convincing than you've been here. (right, in my dreams, your favorite expression to refute history.) If and when the day comes where the Jon Risch method for non linear distortion measurement and analysis replaces the existing and become de rigeur, you will earn my respect which I will gladly announce in public. But until that day, I'll just sit back and watch to see what happens in the real world.

FLZapped

09-16-2004, 07:05 AM

You can characterize my comments as hyperbole or posturing if you like but the sharpest criticisms I can level will be as nothing compared to what this theory will face by the huge corporations like HP who manufacture the worlds finest instrumentation and who will defend their technology and the underlying science behind it. Guess who I'm putting my money on.

Except that they are now known as Agilent.

Unless you've worked in industry, you have no concept of how hard manufacturers work to tear down their own products to find out exactly what the limits of their capabilities are.

Indeed, most people would here would pass out if they ever sat through a real engineering design review.

As Skeptic has pointed out, Jon has no real evidence that his methodology is any better, nor any more elegant that what we already use. In fact, I have pointed out some of it's short comings, which Jon cannot adequately address, except to say you need a huge amount of computing horseppower to support it. Why, when what we currently have is elegant, transportable, accurate, and obvious to implement and interpret.

Quite frankly, his design of it is based soley on speaker systems. Which is obvious by the seperation of the tonal groups; One falls in the low frequency driver range, while the other in the high frequency driver range.. As I said earlier, I believe he dreamed this up to support his belief in bi-wiring. Even so, it is still unecessarily complex to measure what he is trying to achieve and has no useful application in electronic circuitry, much less speaker systems.

-Bruce

skeptic

09-16-2004, 07:28 AM

"Indeed, most people would here would pass out if they ever sat through a real engineering design review."

Design review? That doesn't even begin to tell the story. They put them in thermal cycling chambers to see what happens if they are repeated exposed to extremes of temperature, in humidity chambers, in rf and acoustically shielded rooms to measure all types of emission. They may drop it off the roof of a building or run over one with an automobile. They'll test it at every conceivable voltage to see just where and how it will blow up. As for performance, the design and performance is checked over and over again and compared to the competition. Field surveys to see what customers like and don't like about them. Not just in industry but in colleges where post doctoral researchers are using them every day to perform leading edge research. Every reported field failure is documented to find out why it happend. And then when they have amassed as much data as they can, they go back to the drawing board to start all over again. Meanwhile, other scientists and engineers are working on the next generation of equipment to see if they can punch any hole they can find in the basic concepts and design as well as incorporate new features which will be useful to the end user and give them an edge over the competition. Mr. Risch will be chasing a 100 mile an hour train which is already far down the tracks and he will not only have to catch up to it, he will have to pull out ahead of it and beat them at their own game. They don't just dabble in this. It's their life's work. And they are a team with diverse skill sets including many most of us have never even heard of. Not just one company. Every big company in the business. As I said, it's a very steep uphill battle to overthrow the existing theory and practice. Can one individual do it alone? As I said, I'll watch and see. I'm betting on the establishment. The world of internet chat boards and consumer magazines is kindergarten compared to the world these guys play in.

Resident Loser

09-16-2004, 07:43 AM

...re:"if it's more expensive, it must be better"

Check this out:

http://www.vmpsaudio.com/dc31.htm

---AND---

re:"...I'm sure glad that we're not stuck with those dreadful early sixties SS amplifiers today, despite their "better" measurable performance..."

Let me posit this thought...many early CDs got a bad rep due to the fact that most of the analog program material was mastered, mixed and otherwise hocus-pocused on equipment contemporaneous with the performance, for home playback on similar vintage stuff...consequently the transfer to digital was less than stellar...soooo...back to the masters...here a tweek, there a tweek, everywhere a tweek-tweek...new learning curve for the new medium...

Since most of the stuff played back thru those "dreadful" amps was probably produced on tubed-gear, for playback on similar gear(and let's not discount the fact that true "audiophiles" of the era were lstening predominantly listening to classical, using Mac and Marantz and Fisher and HHScott et al) IMHO you have a similar problem...particularly since the recording companies are loathe to retool and/or retrofit for any reason, particularly for the "pop" crowd...

So, I don't think things reached an "equilibrium" of sorts, until the record producers sprung for the SS stuff and used updated techniques as required in the recording process.

Perhaps the SS amplifiers weren't the problem and it was simply the software "incompatiblities"...

Early SS guitar amps did did just-plain-$uck, however...

jimHJJ(...although my vintage "Pignose" is a hoot and a half...)

FLZapped

09-16-2004, 08:00 AM

E-Stat

09-16-2004, 09:20 AM

Check this out:

http://www.vmpsaudio.com/dc31.htm
No revelations made there by Mr. Cheney. Questions of mid-fi vs. high end aside, there are simply more entertainment choices and reduced fidelity, yet popular formats for music such as MP3 available today that have drastically reduced the number of folks who simply sit down to listen to music. Before you cry elitist regarding my MP3 comment, consider that I am listening at this very music to MP3s stored on my computer. I ripped all my CDs. There's no denying the convenience of having one's entire musical library immediately accessible. It works great for background listening which is really what most folks do.

re:"...I'm sure glad that we're not stuck with those dreadful early sixties SS amplifiers today, despite their "better" measurable performance..."

Let me posit this thought...many early CDs got a bad rep due to the fact that most of the analog program material was mastered, mixed and otherwise hocus-pocused on equipment contemporaneous ...
We're talking about different animals here. I am referring to the earliest players, not recordings. Perhaps you never suffered with a first gen unit. I had an early Magnavox unit (really Philips) that I gave to my Mom when I moved to a Pioneer unit. I listened again to that unit a few years back when she passed away. Nope - it still sucks with new recordings. My $69 Toshiba 3950 DVD player of today is significantly smoother in the high frequencies. BTW, the earliest Telarc recordings mastered on the 16/50 Soundstream system remain pretty darn good today. Conversely, I have some remastered Astrid Gilberto recordings from the early sixties that sound quite clear on my current rig, albeit replete with ping-pong stereo effects, limited bandwidth, and in a couple of cases, gross analog distortion.

Since most of the stuff played back thru those "dreadful" amps was probably produced on tubed-gear, for playback on similar gear(and let's not discount the fact that true "audiophiles" of the era were lstening predominantly listening to classical, using Mac and Marantz and Fisher and HHScott et al) IMHO you have a similar problem...particularly since the recording companies are loathe to retool and/or retrofit for any reason, particularly for the "pop" crowd...
Really don't know where you're going here. The AR integrated amplifier (my first step up from an Electrophonic 8-track unit) remains a hard sounding amp. The Crown IC-150 preamp still drags fingernails across the chaulkboard with your choice of recording.

Perhaps the SS amplifiers weren't the problem and it was simply the software "incompatiblities"...
Then again ! :)

rw

J Risch

09-20-2004, 09:25 AM

In fact, I have pointed out some of it's short comings, which Jon cannot adequately address, except to say you need a huge amount of computing horseppower to support it. Why, when what we currently have is elegant, transportable, accurate, and obvious to implement and interpret.

As I had feared, you fail to fully comprehend what the new tests signal is all about, and what it accomplishes.

I have more than adequately addressed the majority of your comments and concerns, leaving only the one about ease of use/transport of the results. I have posted a reply to that aspect as well, and pointed out some simple expediants that would allow one to compare DUT's visually if nothing else.

Quite frankly, his design of it is based soley on speaker systems. Which is obvious by the seperation of the tonal groups; One falls in the low frequency driver range, while the other in the high frequency driver range.. As I said earlier, I believe he dreamed this up to support his belief in bi-wiring. Even so, it is still unecessarily complex to measure what he is trying to achieve and has no useful application in electronic circuitry, much less speaker systems.

If you had bothered to actually read the paper, instead of only looking at the pictures at my web site, you would find that I have proposed a number of variations on the Phi Spectral multitone, rather than just one single set of tones.

The single graphic example at my web site is what I call a Hi-Lo Split Band Phi Spectral. This is one out of approx. 5 different major variations I came up with.
After further research, I believe that testing with just 3 or 4 of them would suffice to give a pretty good picture of what was going on with a given DUT.

For the paper, See:
http://www.geocities.com/jonrisch/PhiSpectral1.htm
and the next two pages. The text is all there, as are the specifc frequencies I recommend.

[ Even so, it is still unecessarily complex to measure what he is trying to achieve and has no useful application in electronic circuitry, much less speaker systems. ]

This is not true, and I have posted sufficient replies for folks with the knowledge to understand why. I think that your reaction and comments have bee a knee-jerk reaction to me, rather than the actual content and idea's, and that you have made all of your judgements based on the one graphic at my website.

The Phi Spectral multitone has a wide application to electronic circuits, and has already detected a heretofore unknown aspect of CD player behavior with regard to digital filter clipping differences between brands and models of digital filters.

As for it's use with loudspeakers, this could quite possibly be the most powerful and useful distortion test signal ever applied to loudspeakers in the history of measurement. It should be considered indispensable for any loudspeaker system or transducer designer.

Jon Risch

FLZapped

09-20-2004, 01:10 PM

As I had feared, you fail to fully comprehend what the new tests signal is all about, and what it accomplishes.

Sure I have and that's not much.

If you had bothered to actually read the paper, instead of only looking at the pictures at my web site, you would find that I have proposed a number of variations on the Phi Spectral multitone, rather than just one single set of tones.

I did. I wasn't impressed.

This is not true, and I have posted sufficient replies for folks with the knowledge to understand why. I think that your reaction and comments have bee a knee-jerk reaction to me, rather than the actual content and idea's, and that you have made all of your judgements based on the one graphic at my website.

Sure it is, it's easy to show why mathematically. I read your paper, remember.

The Phi Spectral multitone has a wide application to electronic circuits, and has already detected a heretofore unknown aspect of CD player behavior with regard to digital filter clipping differences between brands and models of digital filters.

So say you. Using your signal to characterize clipping would be about as useful as using pink noise for the same.

Sorry Jon, but you just haven't created anything new that is likely to displace the much more simple and elegant methods already in existance.

-Bruce

RobotCzar

09-20-2004, 04:44 PM

"I think it was Mtry who finally produced a lone story of some audio dealer in Florida who was unable to hear the difference between a Yamaha integrated and his Krell amp, ....."

What you really mean is a "story" that meets all your requirements. Because you think that every person in the world would have to be tested on every piece of equipment, your "story" needs will never be satisfied. Instead, I'll ask you to provide any kind of story of a person that can distinguish level-matched, properly performing amps. You know what, there ain't any--not even one ole' story of a guy in Florida. There are plenty of references to blinded, level-matched amp tests over the years, from Stereo Review, High Fidelity, Audio, The Audio Critic,etc. I'm sure you will find something wrong with all these reports because they didn't use "today's" stuff. So go ahead an silence all us irrationals who are out to spoil your fun and show that you can tell your amp from a low end Pioneer reciever. I don't think you can. I'd bet big money on it.

"Fact" has yet to be established from my standpoint. See above".

"It is also true that when you ask ten audio engineers that same question, you will get ten different interpretations."

How would you know? You haven't asked them. Be aware that the term "audio engineer" often means a "recording engineer" who knows how to work a mixer and learned on the job. Why not ask a scientist or an EE? I have often begged people of your beliefs to do so. They generally refuse. You know, "science can't be trusted and all..."

"I will also agree that any subjective opinion of musical reproduction naturally involves a set of priorities established by that listener."

I said more than that, I said that a purely subjective opinion will only be valid for the person who holds it. Why bother sharing your subjective opinions?

"You continue to harp on the "if it's more expensive, it must be better" notion. "

No, I attribute that opinion to you. You have said many things like "it is ridiculous to think that better components won't sound better". I suppose one must think that if one has spent a lot of money on stuff. I prefer evidence.

"In the final evaluation, it is the continuous process of questioning our realm of known science that betters the technology. We all benefit."

There is a big difference in reasonable questioning of valid issues supported by logic, theory, and evidence and simply making up any excuse for believing what you want to believe.

I am more than a little disappointed that you did not respond about your belief that "simple test tones" are inadequte to evaluate the distortion and frequency response of audio electronics. If you really have an open mind and really want the facts, you will find out about this issue. (Please, NOT from Jon Risch, who is not a scientist, it is doubful he is the EE is claims to be.)

I have agreed with you that a single 1KHz spec is not sufficient to characterize the electrical performance for a audiophile, one must test severa freqs across the audible band. But, there is no reason not to use test tones. A 20 Khz test tone at full volume is going to test how "fast" your amp is better than all the goofy spew put out by non-technical audio crackpots.

Having said that, a single 1KHz distortion spec is probably a good idea for most consumers (including most so-called audiophiles). I very much doubt you would distinguish amps with identical distortion at 1 KHz.

No need to respond. This is my liast post in this forum.

Good luck.

Robot Czar

E-Stat

09-21-2004, 09:29 AM

What you really mean is a "story" that meets all your requirements.
Nope. I mean simply results > 1 with equivalent gear

How would you know? You haven't asked them.
That assumption would be wrong.

Why not ask a scientist or an EE?
You're batting zero on the wild guesses. I have spoken with about half a dozen EEs who design and build audio equipment.

You have said many things like "it is ridiculous to think that better components won't sound better".
You mistake me for someone else.

I am more than a little disappointed that you did not respond about your belief that "simple test tones" are inadequte to evaluate the distortion and frequency response of audio electronics.
I use deductive reasoning. If something measures great using one criteria and yet sounds bad, then that criteria is insufficient. My evidence, however, is based upon experience thus I do not post it here.

This is my liast post in this forum.
Good luck to you as well and happy listening.

rw

J Risch

09-21-2004, 04:54 PM

RE this post's comment by you, your replies have far from shown what you have claimed (the following are quotes from FLZapped's previous posts):

"1) You can ONLY measure harmonic distortion with a single test signal."
"2) You ONLY need 2 test signals to measure IM."
and
"It is exactly what I said; Two tones and you get Intermodulation products of a non-linear device."
" Exactly, but why bother to sweep, either you are going to see harmonic distortion generated by the non-linearities of the device, or you aren't."
" Once again, you are going to generate intermodulation products if your device is non-linear, period. Two tones is all that is required to predict and see all products."
"The physics don't change with the operating frequency."
" Your multi-tone test signal is completely unusable to measure intermodulation distortion and is a violation of the recognized definition in measuring harmonic distortion."
"The problem is, your test signal will generate SO many products it would be impossible to distinguish noise from distortion products making it unusable as a viable test signal."
"It is completely unusable to make meaningful measurements."

I have responded to, and answered all of these claims.

You CAN measure HD with more than one tone present, you just have to do it properly, using a multitone signal like the Phi Spectral, which avoids the cover-up and stepping on the various distortion products by the other distortion products. That is the new idea behind the Phi Spectral, which a lot of folks never catch on to.

If you measure IM ONLY using two tones, you will not have characterized the DUT for ANY other combination of tones, ONLY for those two specific tones used.
All of the classic two tone IM test signals tend to measure out differently on a great many audio components. This proves that usng ONLY two tones, you will NOT see what the actual non-linearity of the DUT is.

Audio devices have a bandwidth in terms of octaves FAR in excess of any other type of amplifier or electronic device, including RF. This is what makes the simple linear equations used to generate the 2nd order intercept and the 3rd order intercept for RF amps WRONG for most audio devices. HD at 1 kHz is not going to measure the same as HD at very low or very high audio frequencies, nor is a single pair of IM tones going to provide the full bandwidth behavior of the DUT. The physics DO change with frequency!
(and level, and signal history, etc.)

The Phi Spectral multitone can and has been used to measure HD, THD, IM, Total IM, and Total Distortion, all with one test signal applied. The classic single sine wave for single frequency HD can not do this for the whole audio band when only one frequency is used, nor can the classic two tone IM test signals, nor can the heretofore available multitone signals.

ALL distortion products can be measured, can be distinguished from the noise, and can be calculated as noted above.

So say you. Using your signal to characterize clipping would be about as useful as using pink noise for the same.

Sorry Jon, but you just haven't created anything new that is likely to displace the much more simple and elegant methods already in existance.

As a matter of fact, when a DUT clips the Phi Spectral multitone, a host of distortion products arise in the clear area inbetween the primary test signal tones, and clearly indicate clipping, and whether or not it is asymmetrical, or symmetrical, or if it has a poorly behaved recovery, etc. Far more can be determined using the Phi Spectral multitone than with a single pure tone, or two tones.
(An aside: I suppose that you think that all audio devices clip at the same point at all frequencies too, eh? Once again, this would be false.)

As I said earlier, some folks "get it", and some don't. I think we can clearly see what category you fall into.

Jon Risch

J Risch

09-21-2004, 05:12 PM

(Please, NOT from Jon Risch, who is not a scientist, it is doubful he is the EE is claims to be.)

You have taken several pot shots at me, without bothering to respond directly, and your comments seem based on others perceptions and comments, rather than on your own understanding (or lack thereof). Reminds me of mtrycrafts.

Since you have not provided any proof of your asssertions or claims regarding me or the new test signal, I can only assume that you have no such evidence or proof, just personal opinion formed from reading other posts. The points in those other posts have been effectively rebutted. If you have any evidence or proof, please cite it, otherwise, I wish you would indeed make good on your promise, and cease posting here.

RE my credentials, I am a Senior Project Engineer at Peavey Electronics, a member of the Audio Engineering Society for 24 years who has presented 3 papers, and have 3 US patents (and 2 more pending) to my name. I post under my real name, as I have nothing to hide. What is your real name, and what are your credentials?

Jon Risch

J Risch

09-21-2004, 05:49 PM

Jon, I'd appreciate it if you could elaborate on what you meant about the "past signal history" portion of this statement:
That's a new one for me.

Some audio devices, most notably power amps (but not ONLY power amps) can vary how they respond in terms of distortion based on the past history of the signal.

A trivial example would be the thermal heating of a power amp (output transistors, emitter resistors, various portions of the PS) with a sustained LF signal such as an organ note, and then a cymbal crash right afterward compared to just a naked cymbal crash without the prior sustained LF signal. The amp will react differently, and the distortion will be different.

A more esoteric example would be when electrolytic caps are used to couple the AC signal, or in feedback loops, or in portions of the circuity that provide a bias point or operating voltage reference, the DA of the electrolytic cap can become a significant factor, and cause the operating points to vary with signal content and level. It helps to realize that the DA of many electrolytics can be as high as several percent, and some of the modern super miniature electrolytic caps are the worst, with DA in the realm of 10% or higher. This is enough to actually shift the voltages/currents that they are providing a reference for.

Some audio circuits do not behave well when faced with strong high level asymmetrical transients, they can shift their internal operating points, or a DC servo can saturate, causing a DC output offset shift that varies with transients or signal content, etc.

Usually, examination with a simple single test tone will not reveal these kinds of behavior, but a multitone has enough crest factor and enough slew to push such devices into non-linear operation, similar to the difficult musical portions, and show the distortion occuring. The first example would not be covered as well, but some of it would manifest to some degree.

I have developed several new variations and additions to the original Phi Spectral multitones, some of which explore LF envelope behavior, and others which focus on low level loss of detail (signal information). I really need to do a new paper, and present these to the engineering community as well, before nature or my health put a premature end to my time on this planet. :-( However, I really want to get my book on crossover design done first.

Jon Risch

FLZapped

09-22-2004, 10:27 AM

A trivial example would be the thermal heating of a power amp (output transistors, emitter resistors, various portions of the PS) with a sustained LF signal such as an organ note,

For how long? 30 minutes? Of course, you're ignoring that most who wish to test this will pre-condition the amp by running pink noise through it for a period of time, like 30 minutes, first.

and then a cymbal crash right afterward compared to just a naked cymbal crash without the prior sustained LF signal. The amp will react differently, and the distortion will be different.

Sounds like an impluse test to me.....

A more esoteric example would be when electrolytic caps are used to couple the AC signal, or in feedback loops, or in portions of the circuity that provide a bias point or operating voltage reference, the DA of the electrolytic cap can become a significant factor, and cause the operating points to vary with signal content and level. It helps to realize that the DA of many electrolytics can be as high as several percent, and some of the modern super miniature electrolytic caps are the worst, with DA in the realm of 10% or higher. This is enough to actually shift the voltages/currents that they are providing a reference for.

Still sounds like an impulse test.....

Usually, examination with a simple single test tone will not reveal these kinds of behavior, but a multitone has enough crest factor and enough slew to push such devices into non-linear operation, similar to the difficult musical portions, and show the distortion occuring. The first example would not be covered as well, but some of it would manifest to some degree.

Hmmmm....still seems like a job for a simple impulse test to me.

Once again, much more simple and elegant means are availble to get the job done that are self-evident in their outcome.

-Bruce

skeptic

09-22-2004, 11:06 AM

"A trivial example would be the thermal heating of a power amp (output transistors, emitter resistors, various portions of the PS) with a sustained LF signal such as an organ note, and then a cymbal crash right afterward compared to just a naked cymbal crash without the prior sustained LF signal. The amp will react differently, and the distortion will be different."

Finally something we can agree on. Although the FTC measurement method requires a preconditioning of operating the amplifier with all channels driven to 1/3 rated power for twenty minutes to heat them up, the changes by sustained high power demands can alter the performance of amplifiers. For one thing, heating is a very real problem with vacuum tubes and bipolar transistors because their characteristic curves change. This shows the enormous advantage properly stablized amplifiers using negative feedback have over amplifiers with no negative feedback since the gain is far less dependent on variables such as power supply voltage and temperature. Non negative feedback amplifiers performance drift all over the place. They may never reach a stable operating condition. It also shows why emitter resistors to prevent thermal runaway in bipolar transistors are so important. It demonstrates that in today's technology, the field effect transistor which is inherently thermally stabalized is the device of choice for audio amplifiers. It also shows the effect of poor power supplies whose bias voltage can be pulled down significantly by sustained high power demands and which may not recover without oscillation or other transient instability when overloaded. The effects of all of these aspects of amplifier performance howerver can be quantitatively meausured using standard methods for IM and Harmonic distortion. What is really required is a change in the test procedure to demonstrate the differences between amplifiers rather than the similarities as we have today. They really have to be pushed to their limit and beyond. No standard test that I am familiar with even remotely simulates the real life operational conditions of driving a loudspeaker and some loudspeaker systems with their high back emf and highly reactive low impedence loads present amplifiers with terrible challenges they are not designed to meet. The caution not to use the current crop of low end A/V receivers with speakers of less than 8 ohms is only the most grudging concession to this limitation of their real life performance. Not that they won't merely perform adequately, but that they are prone to failure under such conditions.

"I really need to do a new paper, and present these to the engineering community as well, before nature or my health put a premature end to my time on this planet. :-( "

I cannot believe there will ever come a time when this board and Cable Asylum will not be graced with your "unique" observations and opinions. After all, only the good die young. Just watch out for a little girl with a dog, three weird friends, and a bucket of water.

J Risch

09-22-2004, 08:55 PM

For how long? 30 minutes? Of course, you're ignoring that most who wish to test this will pre-condition the amp by running pink noise through it for a period of time, like 30 minutes, first.

Tsk, Tsk. For the IHF/FTC style testing, you do the pre-conditioning only for the power rating portion of the test (which has distortion limits), but this is NOT the segment of the test regime where you actually run the distortion test portion for the specs.

Sounds like an impulse test to me.....

A simple single impulse would not evoke the same kind of reaction from the amp as what I described. Not enough sustained energy is demanded, just a quick blip, and it's over.

Besides, how does this three times repeated call for impulse testing jibe with your mantra:
"You only need one tone, no, make that two tones, no, make that one tone, wait a minute.... "

You just shot your self down Bruce. Your stance was that a single frequency HD measurement and/or a single IM measurement, and you now knew what the DUT distortion behavior was. Why would you need to use an impulse if these other two were all that was required?

BTW, there is an interesting paper at AP web site about Nonlinear Distortion, see:

http://www.audioprecision.com/bin/Comparison_of_Non-linear_Distortion_Measurement_Methods.pdf

"Comparison of Non-linear Distortion Measurement Methods" by Richard Cabot.

His list of 6 things that can increase HF distortion, and 5 things that can increase LF distortion (over the levels present in the midband), pretty much shoots down your contention that a simple linear equation describes the distortion for an audio device.

So does the listing of distortion for the various test circuits he shows the measurement results for.
Note very carefully that NONE of the IM tests measure the same, nor do they correlate entirely with the THD measurements. See Figures 8 thru 17.

We see in this paper that HD levels vary with frequency, and with level, as do IM distortion levels. This pretty much puts to rest your ridiculous contentions as outlined in my post #92 at:
http://forums.audioreview.com/showpost.php?p=52425&postcount=92

I fully expect an attempt by you to repeat some of the same tired old claims that have already been thoroughly addressed and rebutted, but that won't change the facts of the matter.
Pretty much every thing you have said about the Phi Spectral multitone test signal is wrong, in error, or irrelevant.

Jon Risch

FLZapped

09-23-2004, 10:09 AM

Tsk, Tsk. For the IHF/FTC style testing, you do the pre-conditioning only for the power rating portion of the test (which has distortion limits), but this is NOT the segment of the test regime where you actually run the distortion test portion for the specs.

Just applying a similar methodology to your posting, Jon, never mentioned IHF/FTC. I guess that makes your test invalid too.

A simple single impulse would not evoke the same kind of reaction from the amp as what I described. Not enough sustained energy is demanded, just a quick blip, and it's over.

What you described was an impulse following a sustained envelope, not the two superimposed on them.

Besides, how does this three times repeated call for impulse testing jibe with your mantra:
"You only need one tone, no, make that two tones, no, make that one tone, wait a minute.... "

Oh lookie here, no argument, so we're back to the ol' ad hominem attack. I never said that and you know it, Think I'm goign to call you MM the second, or did he learn from you?

[quote]
You just shot your self down Bruce. Your stance was that a single frequency HD measurement and/or a single IM measurement, and you now knew what the DUT distortion behavior was. Why would you need to use an impulse if these other two were all that was required?

Never said that either, Jon. You're trying to reach outside the scope of the argument here in a vain effort to try and make you test signal viable. I just countered with a much more simple and elegant way of dealing with the problem you presented.

-Bruce

FLZapped

09-23-2004, 10:50 AM

BTW, there is an interesting paper at AP web site about Nonlinear Distortion, see:

http://www.audioprecision.com/bin/Comparison_of_Non-linear_Distortion_Measurement_Methods.pdf

"Comparison of Non-linear Distortion Measurement Methods" by Richard Cabot.

What a waste of time. This paper was nothing more than regurgitation of what is already well known and well documented. I didn't see a single bit of new ground broken. Much like Jung's paper on capacitor distortion. And much like your test signal, this one too takes a large amount of computing power to even hope to get results, nor does it point to being any more accurate than what is already in existance and much easier to implement and interpret.

His list of 6 things that can increase HF distortion, and 5 things that can increase LF distortion (over the levels present in the midband),

And nothing new in the lot of them. Yawn....

pretty much shoots down your contention that a simple linear equation describes the distortion for an audio device.

Never said that, Jon.

The problem with the methodology described in this paper and your test signal is that there is no manual way to verify that you are getting reasonably correct results as there are with the current more simple methodologies that have made it through the standards process and withstood the test of time.

-Bruce

J Risch

09-23-2004, 03:47 PM

FLZapped

09-23-2004, 05:34 PM

You really don't get it, or are refusing to see the light.

Your comments and claims are on record, and to try and deny them is the silliest thing to attempt. Your claims have been rebutted, and your comments are shown to be a slanted and personal view that has no relationship to reality.

End of any further attempts to explain things to you Bruce, it is futile and not worth the effort.

Jon Risch

Thank you, because I'm tired of your hand waving and endless twisting of the facts. If you insist on further hand waving, at least shave your armpits. Nowhere have you actually presented a convincing argument or brought forth any relevent facts that conclusively proves your position.

So if you want to come back for more, maybe we can talk about the proof you have for dielectric sound. silver sounding bright, multiple phase reversals in coaxial cable that is less than a tenth of a wavelength, noise in wire, and your completely unproven listening methodology that supports your theories, yet no one else in the world has verified any of your claims with any method, much less yours.

Bogus theories that you have yet to prove....just like you haven't proven any real usefulness for your phiddle-phaddle test signal.

-Bruce

ToddB

09-23-2004, 11:25 PM

What Jon claims he did and what Jon can actually produce are two different things.
So I take it that you've performed tests using Jon's method and produced measurements that contradict his? You do remember what forum this is, right, and you're not just making an unsupported claim based on personal experience here? Bwahahahaha.....;)

If you had the history with him that many of us do, you would immediately know this without explaination. :)
My history with Jon is quite sufficient for me to have arrived at a judgement as to the value of his perspective.

I didn't say the results are invalid, just unusable. Like that old quip: "Too many cooks spoil the broth" - too many test tones spoil the test.
Again, you're not accounting for the results Jon has already posted. If you disagree with his results, then you must believe that he's either lying or that his calculations are wrong. Which is it?

One other thing you have to understand is that these tests must be able to be performed outside the engineering lab. Make it too complicated makes it unusable anywhere but the engineering lab. Okay, so how is a tehnician out in the field going to be able to relate his findings to an engineer if they aren't speaking the same "test language" because he cannot perform this test and be able to interpret the results?
I see that Jon has already responded to this. While the principle you espouse is certainly legitimate enough, this particular application doesn't appear to stress that principle to any large degree.

ToddB

09-24-2004, 01:04 AM

And enough with the personal insults, everyone. If you can't say something without insulting somebody, then don't say it.

markw

09-24-2004, 05:31 AM

It's just that it seems nobody EXCEPT Jon has ever seen the validity od his approach.

And, as I said in my first post on this subject, the experts still haven't evaluated it, at least those you consider experts anyway. While professional in their fields you don't accept their opinions because they don't agree with Jon's?

Quite a few have torn it apart here but apparantly that's not enough for you. Howsa bout getting some of those guys from the AES to come to his defense. You're the one that brought that up in he first place.

As it now stands, 9 out of 10 doctor's do NOT recommend Crest. ...and that doesn't seem to be changing any time soon.

skeptic

09-24-2004, 06:09 AM

I think it's only fair to let the AES look at his paper and see if there is any merit in what he says. Personally, as I've said, I don't see any. However, people who know much more about it than I do will have the chance to examine it carefully, challenge it, tear it apart, and if they can't shoot it down, adopt part or all of it. I hope he lives long enough to see the results. From what he alluded to in his other posting, it seems like he's expecting to pass away in the not too far flung future. Developing a test method to prove his theories about audio cables seems to be part of his life's crusade.

I must say that while I don't agree that his method offers anything new or necessary, I at least agree with him to the extent that the current procedures for evaluating much in audio equipment is inadequate because it doesn't show us the differences that exist. The state of the art of design has far surpassed the state of the art of measurement or at least the commonly used procedures. Equipment should be pushed well beyond the current limits by tests which demonstrate electrical performance differences which correlate with real world audible differences. However, unless there is a sound mathematical foundation to support the measurement theory, guesses like saying that the current test procedures mask distortion or that there is a correlation between what he measured whith his procedure and what sounds good to some people isn't adequate. While I've seen all kinds of graphs of waveforms and tabulations as well as very long explanations and references in his presentations, I do not recall seeing even one mathematical formula. When he says that the distortion is masked, he needs to back it up with equations showing how and why and others to show how and why his procedure overcomes the problem. As far as I can tell, he hasn't done that. And he hasn't shown why the current test equipment which can measure such infinitesmal distortion levels gives erroneous results. All I have is his verbal assurances which are not adequate for me. I don't think that they will be adequate for the AES either. Also, it is surprising that someone would want to introduce a new theory on an internet web page and defend it staunchly before having peer review acknowledge its worth. This is the kind of bravura which opens people up to ridicule but that seems more common than ever these days.

FLZapped

09-24-2004, 08:16 AM

So I take it that you've performed tests using Jon's method and produced measurements that contradict his?

Nothing to contradict, there is nothing from Jon in the first place, except handwaving. Besides, it has nothing to do with actual measurements, but whether or not his test signal has any merits in the realm of equipment testing, so far, he has failed to show that it can, or will, subplant anything currently in existance that is simpler and easier to implement and interpret.

My history with Jon is quite sufficient for me to have arrived at a judgement as to the value of his perspective.

tha is because jon hangs out in quarters where he does not receive critical scrutiney from his peers(or has manipulated the environment to prevent it), rather people of very limited technical knowledge whom he has hoodwinked with his bogus theories. Do a search on the NNTP newsgroups and see what happened to him there when he ran across some of his peers.

Again, you're not accounting for the results Jon has already posted. If you disagree with his results, then you must believe that he's either lying or that his calculations are wrong. Which is it?

What calculations? I have yet see a single calculation from him. As for his data, it is scant and flawed. Go over to AA and look up Steve Eddy's discussion on the matter. Further, you missd the point entirely, has nothing to do with making measurements, but whether the test signal has any real value, if it does something unique that can't be reproduced by any other means, or if it simplifies current methodology. Jon hasn't shown anywhere that it does.

-Bruce

FLZapped

09-24-2004, 08:20 AM

I think it's only fair to let the AES look at his paper and see if there is any merit in what he says.

As far as I know, he has already submitted it.

-Bruce

FLZapped

09-24-2004, 08:26 AM

When he says that the distortion is masked, he needs to back it up with equations showing how and why and others to show how and why his procedure overcomes the problem. As far as I can tell, he hasn't done that. And he hasn't shown why the current test equipment which can measure such infinitesmal distortion levels gives erroneous results. All I have is his verbal assurances which are not adequate for me.

Too bad the archives here are lost. He has on more than one occasion tried to say it is because the commonly available test equpment uses averaging. Of course the flaw in that argument is that the measurement is steady-state and the use of averaging acutually improves the noise floor by averaging it out, because it is an uncorellated(random) signal, and therefore actually improves the measurement accuracy.

-Bruce

E-Stat

09-24-2004, 11:32 AM

I at least agree with him to the extent that the current procedures for evaluating much in audio equipment is inadequate because it doesn't show us the differences that exist. The state of the art of design has far surpassed the state of the art of measurement or at least the commonly used procedures. Equipment should be pushed well beyond the current limits by tests which demonstrate electrical performance differences which correlate with real world audible differences.
Extraordinary. Gee that's my feeling exactly !

rw

skeptic

09-24-2004, 04:36 PM

Not so fast. I'm only back for this one thread because I don't want to see somebody get away with something of questionable merit unchallenged.

I belive in torturing captives. Captive terrorists, captive amplifiers. Make it cry. Make it howl in pain. Push it to the limit and then some. Break it if you have to. They do it with cars. Why not with amplifiers? They do it to engineers (I know first hand, my friends and I have been there.) So far at least one has escaped. The AES will put him on the bench and see if he has the stuffing to stand up to the ultimate challenge. Maybe that's why he had his ominous premonition. :-) John Escalier would be miserable without Jon Risch. Who would he argue with so vehemently? Who else cares that much about this crap?

E-Stat

09-24-2004, 07:13 PM

Who else cares that much about this crap?
Musiclovers who don't buy the company line because they know better.

rw

ToddB

09-25-2004, 01:55 AM

Nobody is insulting anybody.
Bruce telling Jon to shave his armpits was childish and insulting. I'm surprised that I'm having to explain this to you.

It's just that it seems nobody EXCEPT Jon has ever seen the validity od his approach.
I see validity to his approach, I've seen nothing in this thread to dissuade my curiosity about it, and I fully intend at some point to perform the tests on my own equipment to see what kind of results I get. Actually performing the measurements would be the one guaranteed way to determine if Jon's method has any validity, which may be why nobody who has shown up in this thread to rail about the supposed flaws in his method claims to even have tried it.

And, as I said in my first post on this subject, the experts still haven't evaluated it, at least those you consider experts anyway. While professional in their fields you don't accept their opinions because they don't agree with Jon's?
And as I said in my first post on this subject, I was asking for opinions on the validity of the test from the people who frequent this board, I did not ask for a peer reviewed evaluation from any experts. Also, I would have no problem accepting an opinion that disagreed with Jon's, were a compelling argument justifying that opinion to be presented.

Quite a few have torn it apart here but apparantly that's not enough for you. Howsa bout getting some of those guys from the AES to come to his defense. You're the one that brought that up in he first place.
You must only have internalized one side of this discussion, because Jon has addressed every concern that's been raised. He also doesn't appear to need anyone else to defend him, because his explanations are intelligent and quite reasonable, but I suppose I'll find out the truth of the matter when I actually perform the tests myself.

As it now stands, 9 out of 10 doctor's do NOT recommend Crest. ...and that doesn't seem to be changing any time soon.
Then I guess that would be reason enough for you to feel comfortable with your preconceptions, even though a rationale has been posited that may prove those preconceptions to be wrong.

ToddB

09-25-2004, 02:53 AM

Nothing to contradict, there is nothing from Jon in the first place, except handwaving. Nothing? Handwaving? Jon has provided graphs, measurements, and explanations for how he arrived at his results. They're posted for the whole world to see. If you have data that contradicts those results, then let's see it.

Besides, it has nothing to do with actual measurements, but whether or not his test signal has any merits in the realm of equipment testing, I can't believe you actually said this. Jon's method has EVERYTHING to do with the measurements, especially since he claims that those measurements prove to correlate with audible impressions. The measurements are the ENTIRE POINT of the method. How can you possibly not understand that?

so far, he has failed to show that it can, or will, subplant anything currently in existance that is simpler and easier to implement and interpret. Yes, you've made it quite clear that this is your position.

tha is because jon hangs out in quarters where he does not receive critical scrutiney from his peers(or has manipulated the environment to prevent it), rather people of very limited technical knowledge whom he has hoodwinked with his bogus theories. Do spare me the patronizing attitude and conspiracy theories. You've had just as much opportunity to give your side of this issue as Jon's had to give his. If people have found your arguments to be lacking, it's entirely within the realm of possibility that it's because your arguments have been lacking. If you believe that insulting the audience is somehow going to further your argument, it's not, at least not with me.

What calculations? I have yet see a single calculation from him. As for his data, it is scant and flawed. The calculations he made to arrive at the test signals he used. The frequencies he used in those test signals, as a result of those calculations, are posted on his website. The results from some tests are also posted, I assume the unincluded graphs agree with those results, and explanations for how the results were arrived at are given. All of the information is available for you to use in proving that his method is flawed, if in fact you are able to do so.

Further, you missd the point entirely, has nothing to do with making measurements, Like I said, as I read it, this has everything to do with the measurements.

but whether the test signal has any real value, if it does something unique that can't be reproduced by any other means, or if it simplifies current methodology. Jon hasn't shown anywhere that it does. I don't recall Jon ever claiming that his method simplifies the current procedure, and if he did, then I would have to disagree, because it's clearly more complex. The value in that additional complexity, though, would be the claim that the test results are more representative of the audible performance of the equipment under test. Your position that the data Jon has posted is not unique and can be arrived at by more traditional means is not one that I would currently agree with, since I've never seen it anywhere else.

FLZapped

09-25-2004, 04:52 AM

Nothing? Handwaving? Jon has provided graphs, measurements, and explanations for how he arrived at his results. They're posted for the whole world to see. If you have data that contradicts those results, then let's see it.

Graphs? where? YOu mean that link that had that fasttest thing, that isn't his work.

I can't believe you actually said this. Jon's method has EVERYTHING to do with the measurements, especially since he claims that those measurements prove to correlate with audible impressions. The measurements are the ENTIRE POINT of the method. How can you possibly not understand that?

Yeah, he claims, he hasn't sufficiently backed up his claims. Again, you miss the point, and gawd, I repeated it enough. He can't show where his methodology, which he even admits reaquires a ton of computing power to even begin to interpret, is better than any method already available and is more simple, and more easily einterpreted. Find a new argument, please, this one is dead, and rotting already.

Do spare me the patronizing attitude and conspiracy theories.

What in the hell are you smoking?

The calculations he made to arrive at the test signals he used.

WHAT CALCULATIONS? He has never once demonstrated them, beside pulling out a known algorithm and applying it, why do you think it already had a name???

I don't recall Jon ever claiming that his method simplifies the current procedure, and if he did, then I would have to disagree, because it's clearly more complex. The value in that additional complexity, though, would be the claim that the test results are more representative of the audible performance of the equipment under test. Your position that the data Jon has posted is not unique and can be arrived at by more traditional means is not one that I would currently agree with, since I've never seen it anywhere else.

Obviously you have no background in testing and mathmatics. It's already been explained and demonstrated that as you increase the number of test signals, the test signal itself begins to look more and more like noise(much less than when you add all the distortion product into the mix). Noise is not a very useful test signal, if it were, we'd use music, because it is mathematecally indistinguishable from noise.

Again, this is a dead and rotting argument. Please find a new one that is unique.

-Bruce

markw

09-25-2004, 05:00 AM

I see validity to his approach, I've seen nothing in this thread to dissuade my curiosity about it, and I fully intend at some point to perform the tests on my own equipment to see what kind of results I get. Actually performing the measurements would be the one guaranteed way to determine if Jon's method has any validity, which may be why nobody who has shown up in this thread to rail about the supposed flaws in his method claims to even have tried it.This brings to mind a quote from the first Star Wars. “The force has a powerful effect on weak minds, Luke”

Your words from post #68 in this thread:

I don't have any particular technical knowledge or experience related to this subject, so take my opinion for what it's worth, but based on the arguments given in this thread, I'm not seeing a sufficient rationale for taking the position that Jon's test method is without merit.

Your self admitted lack of technical knowledge and experience notwithstanding, there are several here who DO have such experience who dare question the validity, repeatability and usefulness of what Jon proposes. This was pointed out by Bruce, John and Sketic, all of whom have shown a more than passing familiarity with the subject matter at hand. More than you or I. The fact that they don’t simply bow down to him is where your problem lies.

And as I said in my first post on this subject, I was asking for opinions on the validity of the test from the people who frequent this board, I did not ask for a peer reviewed evaluation from any experts.

…and you got them. Be careful what you wish for. You just might get it.

The problem you seem th have is that there are others involved in this field that don’t happen to be swayed by mumbo jumbo. They require proof before buying into a new idea. After that cold fusion thing, it seems a prudent thing to do. …Not to mention David Koereshs Jim Jonsess followers.

Again, you asked for it. It’s your problem that the only “experts” you acknowledge are those that agree with you.

You must only have internalized one side of this discussion, because Jon has addressed every concern that's been raised. He also doesn't appear to need anyone else to defend him, because his explanations are intelligent and quite reasonable, but I suppose I'll find out the truth of the matter when I actually perform the tests myself.

Again, I refer to your words from post #68 in this thread:

I don't have any particular technical knowledge or experience related to this subject, so take my opinion for what it's worth, but based on the arguments given in this thread, I'm not seeing a sufficient rationale for taking the position that Jon's test method is without merit.

No, you won’t find the truth in anything. Skeptic was kind when he responded to your post 68 that you were out of your league. You may play around with some stuff and, amazingly enough, come to the results you want to get. Should you choose to post your results of this test, you better have your technical chops up to snuff because I’m pretty sure the same techs who took Jon to task here will be more than ready to do the same for you.

Then I guess that would be reason enough for you to feel comfortable with your preconceptions, even though a rationale has been posited that may prove those preconceptions to be wrong.

Yeah, I would always be happy to embrace advancements in audio. I will when one is developed and proven. So far, the jury is still out on this one. It's been around for how long? Nobody has openly adopted it yet? Doesn't that suggest something to you?

I also wanted to believe we had cold fusion to afford cheap, plentiful and clean power too. But, fortunately greater minds than ours saw through the handwaving and promises to the real facts at hand.

J Risch

09-26-2004, 09:42 AM

It's just that it seems nobody EXCEPT Jon has ever seen the validity od his approach.

That's a weird thing to say. NOBODY is all inclusive, and since I have provided some references as far as others who have used it, and others who have cited it in their papers, it is patently untrue. If all you are talking about is the very limited world of AR, here on The Audio Lab, then that is a hoot.

Quite a few have torn it apart here but apparantly that's not enough for you.

Again with the hyperbole. Only two people here, people KNOWN to be hostile to me personally, have attempted to raise issues about the Phi Spectral test signal. I have answered all of the issues raised quite thoroughly, and so, even their "tearing apart" is certainly in question. Who else are you referring to? jneutron asked some simple questions about it, he did not "tear it apart".

Do YOU have anything technical to add, or technical issues to raise? I haven't seen any from you, all I have seen you post about looks just like jumping on along with those other two for the ride.

Your hostility toward me is also well known, so it should not be any surprise that you are going to add your voice to the attempts, but that is all it is, your opinion, apparently based on just two other hostile people.

Jon Risch

J Risch

09-26-2004, 10:50 AM

... I at least agree with him to the extent that the current procedures for evaluating much in audio equipment is inadequate because it doesn't show us the differences that exist. The state of the art of design has far surpassed the state of the art of measurement or at least the commonly used procedures.

I don' think that too many people would argue that a simple single number metric like THD is not showing the whole picture, and that it does not directly correlate with perceived sound quality. Nor would very many argue that a single number metric like SMPTE IM distortion is also inadequate to rank audio device for sound quality.

That is where the new generation of multitone test signals came in, folks, not just me, but lots of others, were looking for something that would work better than the classic THD and IM tests. Note that before I presented my paper at the AES covention in September of 1998, the multitones that existed were an attempt to go beyond the single tone THD/HD measurements, to go beyond the two tone IM measurements. Some of those earlier multitone test measurements had been published in Mix magazine as having correlation with the sound of various studio monitors, others had been highly touted by the companies who developed them, and had created proprietary trade-marked test signals for use with their measurement equipment.

However, unless there is a sound mathematical foundation to support the measurement theory, guesses like saying that the current test procedures mask distortion or that there is a correlation between what he measured whith his procedure and what sounds good to some people isn't adequate. ... When he says that the distortion is masked, he needs to back it up with equations showing how and why and others to show how and why his procedure overcomes the problem. As far as I can tell, he hasn't done that.

I pretty much spell out how and why the other multitone test signals in use prior to my Phi Spectral cover up either a lot, or MOST of the probabvle distortion components.

If we look at one of the ones promoted by Audio Precision, the FASTEST multitone, it should be quite clear, once I have pointed it out, that a multitone test signal that is based on the use of tones at 1/3 octave intervals, will cover up virtually ALL of the harmonics, and most of the IM products, etc. due to this even frequency spacing.

Just to make it crystal clear, let's look at some specifics. The 1/3 octave frequencies are:
20, 25, 31.6, 40, 50, 63, 80, 100, 125, 160, 200, 250, 316, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3160, 4000, 5000, 6300, 8000, 10000, 12500, 16000, and 20000.

Audio Precision does adjust the frequencies to correspond to an FFT analyzer bin center frequency, in order to maximize the ability to use the empty analyzer bins to best advantage. The actual 31 frequencies are: 16.15, 21.53, 26.92, 43.07, 53.83, 64.60, 80.75, 102.28, 123.82, 156.12, 199.18, 253.02, 317.61, 398.36, 500.65, 635.23, 802.11, 1001.3, 1248.9, 1598.8, 1997.2, 2503.2, 3154.6, 3999.8, 4995.7, 6352.3, 7999.6, 10002, 12500, 16005, and 19999 Hz. Note that none of these deviate from the nominal 1/3 octave frequencies by more than 5 Hz, in keeping with placing them in the center of the FFT bin range.

Since we are limited to the FFT bin width in terms of frequency resolution, and this particular AP test uses 5 Hz wide bins (an 8 K FFT), I will simplify things and use the original even number 1/3 octave frequencies for my simple examples.

I will NOT cover every possible example, as doing this would make even one of my more traditional posts look short.

So lets say we wanted to use this FASTEST signal to look at harmonic distortion. OK.
If we try to look at the harmonic distortion of the 20 Hz tone, what happens? Whoa, wait a minute, we can't!
There are primary tones at 40 Hz, 60 Hz, 80 Hz, 100 Hz, etc. By the very definition of a 1/3 octave tone sequence, there are going to be primary tones all across the audio band that prevent us from looking at the HD of most all of the primary tones within the audio band.

What about looking at IM distortion? Well, if we examine the tone sequence for the 1/3 octave FASTEST multitone, we can see that a great many of the tones have spacings that are the same. As one trivial example, we see that we have a 100 Hz tone and a 200 Hz tone, a 400 Hz tone and a 500 Hz tone, a 25 Hz tone and a 125 Hz tone. These all have spacings of 100 Hz differences. If we were to try and look at the IM distortion for the difference tones from these frequency pairings, guess what? There is a 100 Hz primary tone that will cover up all of the distortion products that have a 100 Hz difference frequency.

Same thing for the 200 Hz and 400 Hz pair, the 200 Hz difference tone is covered up by the primary tone at 200 Hz, as is the difference tone from 800 and 1000 Hz, and from 50 Hz and 250 Hz. I would think that you are getting the general idea by now, and I truly hope that I do not need to call out ALL the possible cover-up combinations that an even 1/3 octave spacing of the primary tones causes.

Virtually ALL of the HD products are covered up, and a great many of the IM products as well.

Once we look at the Phi Spectral multitone in this same manner, we can see that virtually ALL of the HD products are NOT covered up by any of the primary tones, nor are they covered up by other distortion products, and that most of the IM products are not covered up in this same manner.

I went through this in my paper, and went through the same excercise for the SYSid default multitone test signal (the one's used in the published reports for MIX magazine, some of these reports WERE available online, but I do not know if they still are) and for the Jensen Spectral Contamination multitone.

All of these multitones had the same basic problem: extensive cover-up of many of the HD and IM products by the primary tones AND by other distortion products.

By now, most folks would get the significance of the Phi Spectral, and how powerful it is, in that it avoids this basic problem, and allows a complete accounting of what distortion is present, and WHERE it came from, that is, what tone or tones generated it.

Yes, one does need the power of a computer to assist in keeping track of all the information present, and to fully extract all of the data from the test tone. What I did for my paper, allows anyone with a decent soundcard, and/or a CD-R burner, and some simple wave file editing/generation software to duplicate my efforts at very low cost.

Several of the major test/measurement instrumentation packages have the capability to generate and run a Phi Spectral multitone, and this includes the AP gear, the SYSid, some of the Rhodes & Schwartz gear, as well as some others that allow for the programable generation of a multitone signal.

Also, it is surprising that someone would want to introduce a new theory on an internet web page and defend it staunchly before having peer review acknowledge its worth.

In terms of defneding it "staunchly", I am doing so, because I know just how much power and utility this signal has, and have been through the wringer on it already: from my own examination for potential flaws and problems. For many a good engineer, their own worst critic is themselves.

As I have stated before, and posted here, I presented a paper to the AES in Sept. of 1998,
and have since received literally hundreds of inquiries regarding the signal.

The vast majority of those people "got it", and wanted to get particulars on the implementation and use of the test signal.

Since then, I have been working on new variations of the Phi Sectral, ones that I hope will allow measurements of such things as "loss of inner detail", and measurements that can show the weighted audibility of the distortion products, thus eliminating the need for a manual look-up table, etc.

Jon Risch

FLZapped

09-26-2004, 01:09 PM

Since then, I have been working on new variations of the Phi Sectral

So obviously, it hasn't set the testing world on fire.....

-Bruce

markw

09-26-2004, 03:00 PM

That's a weird thing to say. NOBODY is all inclusive, and since I have provided some references as far as others who have used it, and others who have cited it in their papers, it is patently untrue. If all you are talking about is the very limited world of AR, here on The Audio Lab, then that is a hoot.Granted, nobody is all inclusive. LEt's say that nobody with enough technical chops to even have a clue what you are talking about here nas endorsed it. The onlyt "real" endorsments you have are faith based.

Again with the hyperbole. Only two people here, people KNOWN to be hostile to me personally, have attempted to raise issues about the Phi Spectral test signal. I have answered all of the issues raised quite thoroughly, and so, even their "tearing apart" is certainly in question. Who else are you referring to? jneutron asked some simple questions about it, he did not "tear it apart"..Well, there's Skeptic and Bruce weighing in on te negative. John E asked a few questions but, as of yet, hasn't endorsed it yet. ...and neithe has anybody else of any repute that I can recall

Do YOU have anything technical to add, or technical issues to raise? I haven't seen any from you, all I have seen you post about looks just like jumping on along with those other two for the ride.

Your hostility toward me is also well known, so it should not be any surprise that you are going to add your voice to the attempts, but that is all it is, your opinion, apparently based on just two other hostile people.

Jon RischTechnical, no. I'm years out of the loop but from your past statements and the ease with which others with the chops have caused you too many curious answers, I've learned to be vewy, vewy skeptical of almost anything you say. Not that I don't think it's possible, but I'd like a few more learned opinions before filling this perscription, doc. I'm still waiting for the 9 out of 10 doctors to use it.

J Risch

09-26-2004, 03:15 PM

So obviously, it hasn't set the testing world on fire.....

-Bruce

See my earlier reply to markw and swerd, post #17 at:
http://forums.audioreview.com/showpost.php?p=51111&postcount=17

Jon Risch

J Risch

09-26-2004, 03:21 PM

... just the two folks here at AR who are known to be hostile to me.

Technical, no. I'm years out of the loop but from your past statements and the ease with which others with the chops have caused you too many curious answers, I've learned to be vewy, vewy skeptical of almost anything you say. Not that I don't think it's possible, but I'd like a few more learned opinions before filling this perscription, doc. I'm still waiting for the 9 out of 10 doctors to use it.

Curious answers? Yet another mechanism to avoid actually having to back up a solid statement or claim on your part.

My answers have been straight forward and on target, and neither Bruce nor skeptic have been able to show a convincing and solid flaw with my statements or reasoning.

In point of fact, you have nothing to go on except your own hostility towards me, no actual technical reasons other than what you see those two others trying to bring up as relevant.
Your opinion on this matter isn't even really your opinion, just repeating what others have said.

Jon Risch

markw

09-26-2004, 04:57 PM

... just the two folks here at AR who are known to be hostile to me.

Curious answers? Yet another mechanism to avoid actually having to back up a solid statement or claim on your part.

My answers have been straight forward and on target, and neither Bruce nor skeptic have been able to show a convincing and solid flaw with my statements or reasoning.

In point of fact, you have nothing to go on except your own hostility towards me, no actual technical reasons other than what you see those two others trying to bring up as relevant.
Your opinion on this matter isn't even really your opinion, just repeating what others have said.

Jon RischLet's just say highly skeptical. I did work with microwaves (ande waveguide) many years ago and I was very familiar with skin effect then and I don't think the rules have changed that much since then, particularly when it comes to what frequencies it affects. A lot of what you espouse is bull, pure and simple. Your takes on the skin effect while perhaps germaine when talking microwaves, is a non-issue in rfeal world audio ye, there you go running around saying the sky is falling.

So, why should I believe this is any different, particularly when you seem to be so against any "real world" controlled testing, except your own, of course. When the IHF or some accredited agency gives their approval by accepting your tests, or at least publicly acknowledging it's validity, then I'll apolgize.

Again, no hostility. I just take anything you say with a big grain of salt and a lot of expert verification, which I ain't seen yet. Ouestioning is not the same as accepting. It's only a first step, much like walking into the auto showroom to look at sticker prices.

ToddB

09-26-2004, 11:28 PM

Beside, why aren't you pissing and moaning about his personal attacks, I even pointed them out for you.Bruce, if you could manage to react with less hysteria, you might notice things like my post that preceded markw's comment including the phrase "enough with the personal insults, everyone". Do you know what the word "everyone" means? The reason I quoted what you said in my reply to markw was because it was a very clear example of one of the insults I was referring to, and markw was apparently in need of a very clear example. If you don't want your particular insults used as examples, then an obvious way to avoid that would be to stop insulting people.

And for future reference, insulting me is one guaranteed way to get your posts deleted, which is what I'm about to do with this post of yours.

ToddB

09-27-2004, 12:31 AM

Graphs? where? YOu mean that link that had that fasttest thing, that isn't his work.
No, I was referring to the graphs Jon said he would e-mail to anybody who wants them, and to which he refers throughout his article and paper. There's also the graph labled "Figure Y" on the first page of the article on his webpage.

Yeah, he claims, he hasn't sufficiently backed up his claims. Not to your satisfaction, obviously. How many times are you going to feel the need to say this? Do you think we don't know what your position is by now?

Again, you miss the point, and gawd, I repeated it enough. He can't show where his methodology, which he even admits reaquires a ton of computing power to even begin to interpret, is better than any method already available and is more simple, and more easily einterpreted. Find a new argument, please, this one is dead, and rotting already. The point, as YOU continue to miss, are the results Jon claims to have generated with his method. You obviously disbelieve those results, I've asked you at least once why you disbelieve them, and you have failed to provide me with an answer to that question that I find satisfactory. So I'll ask again: Jon has claimed a set of results that are generated with his test method, you obviously believe that those results are false, and I would like to know why you believe that.

The only aspect of his test method that Jon hadn't addressed to my satisfaction was what to do with all of the distortion products that were going to be generated with his signal. I wasn't too concerned with this, since I assumed that I would be able to limit the number of products when I ran the test myself, but upon rereading either Jon's webpage article or his paper, I forget which, I discovered I'd overlooked that he was limiting results to the 10th harmonic. So, for me, this addresses the only substantive issue you've raised that I still had questions about.

And you're mischaracterizing what Jon said about computing results. He stated that a common household PC with a sound card would be sufficient for performing this test. The only person I recall claiming that this would require a "ton of computing power" is you.

What in the hell are you smoking?
Nice answer. If you could actually defend your comment, I expect you would have, instead of responding with tripe like this.

WHAT CALCULATIONS? He has never once demonstrated them, beside pulling out a known algorithm and applying it, why do you think it already had a name??? I thought you said you read his paper? He says that he generated the frequencies he used by calculating multiples based on permutations of the golden section numbers. The frequencies derived from that formula apparently failed to work for him for the 12 tone test, so he used different multiples, which he admits were arbitrary, to generate different frequenies for some of the tones.

Obviously you have no background in testing and mathmatics. It's already been explained and demonstrated that as you increase the number of test signals, the test signal itself begins to look more and more like noise(much less than when you add all the distortion product into the mix). Noise is not a very useful test signal, if it were, we'd use music, because it is mathematecally indistinguishable from noise. We're not talking about noise, Bruce, we're talking about a fixed set of tones, no more than 12, whose whole purpose is to produce distortion byproducts that will remain discrete and able to be read. You have more education in this field than I do, so why is it that I am able to grasp this concept and you are not? If you believe that even a limited sample of 12 tones will produce results that are sufficient to render the test useless, then we're back to my question of how you explain the results Jon claims to have generated? As I said before, you must either believe that Jon is lying or that his calculations are wrong. Which is it? A straight answer here would be nice.

Again, this is a dead and rotting argument. Please find a new one that is unique. If you feel that you've contributed all to this thread that you're able to, then stop posting in it. Nobody's forcing you to continue in the discussion.

ToddB

09-27-2004, 01:16 AM

This brings to mind a quote from the first Star Wars. ï¿½The force has a powerful effect on weak minds, Lukeï¿½ More insults? Perhaps because you have nothing useful to offer the conversation?

Your self admitted lack of technical knowledge and experience notwithstanding, there are several here who DO have such experience who dare question the validity, repeatability and usefulness of what Jon proposes. This was pointed out by Bruce, John and Sketic, all of whom have shown a more than passing familiarity with the subject matter at hand. More than you or I. The fact that they donï¿½t simply bow down to him is where your problem lies. Yet more useless static from you. The only problem here appears to be that some people are unwilling to honestly evaluate or consider the procedure because it doesn't conform to the safe, comfortable, and familiar method that they're used to. From my perspective, Jon has adquately responded to every issue that's been raised in this thread. If there are flaws in his responses, nobody here is explaining what they are to my satisfaction.

The problem you seem th have is that there are others involved in this field that donï¿½t happen to be swayed by mumbo jumbo. "Mumbo jumbo", huh? That's the most learned response you have to offer?

ï¿½Not to mention David Koereshs Jim Jonsess followers. And yet more insults...

Again, you asked for it. Itï¿½s your problem that the only ï¿½expertsï¿½ you acknowledge are those that agree with you. You are the one who seems concerned about finding experts to bow down to. I'm looking for coherent explanations.

You may play around with some stuff and, amazingly enough, come to the results you want to get. So now you're a mind reader, and you've somehow devined what results I want to get? For all I know, the results will be exactly the same with Jon's method as they will be for the traditional methods. But then, this comment of yours wasn't intended to actually be constructive.

Should you choose to post your results of this test, you better have your technical chops up to snuff because Iï¿½m pretty sure the same techs who took Jon to task here will be more than ready to do the same for you. All I can do is plug in the tones, read the results, and explain how I performed the test. If I perform the tests as properly as I can, and the results wreck some people's world views, that's not my problem.

Yeah, I would always be happy to embrace advancements in audio. I will when one is developed and proven. I'm not surprised that you're only concerned about what external authority figures tell you is an advancement. The only advancements I've cared about are the ones that improve the quality of my listening experience, whether any "authorities" have proven it or not.

I also wanted to believe we had cold fusion to afford cheap, plentiful and clean power too. But, fortunately greater minds than ours saw through the handwaving and promises to the real facts at hand. Since this comment is so misrepresentative of what actually happened, I assume that you don't know. The cold fusion claim was disproven because other labs attempted the experiment, and all of them were unable to replicate the results of the original two scientists. See how that works, people actually tried out the experiment, and compared the results? That's an intellectually honest approach that goes beyond hypothetical theorizing.

J Risch

09-27-2004, 09:26 PM

Quite a flurry of activity, but all noise and no substance.
Since YOU continue to rail against me, and post the same tired old trash about the Phi Spectral, I need to point out the flaws and errors in your posts, as usual.

In post #127,
http://forums.audioreview.com/showpost.php?p=53183&postcount=127
you said:
" Doesn't change the fact that you cannot generate the signal easily with NBS traceable equipment. According to your paper, you're using a CD."

You aren't really serious about this kind of stance, are you? I provided a very easy way for others to duplicate what I did with a minimum of equipment and investment. This is not a crime or a problem.

As I noted in another post here, the signal can easily be generated via a full duplex soundcard by playing back a previously constructed wave file, and running the sound card with an FFT spectrum analysis program on the input. Other test/measurement equipment can generate and spectrum analyze the Phi Spectral signal, such as the AP System Two, one of the Rhoades & Schwartz units, the SYSid system, etc. One is NOT limited to a CD player as a signal source.

As for NBS tracability, this is not exactly that common among modern computer based THD analyzers or for spectrum analyzers, yet Cabot and many other well respected audio engineers can recommend and use a spectrum analyzer to measue THD and to measure IM, despite a lack of "NBS tracability". You are the one who seems stuck in the past, in love with old General Radio mechanically linked analyzers and THD meters. Just another red herring from you, trying to create another artificial hurdle to jump. Not too many people in the audio industry hang there hat on, or live and die by "NBS tracability".

"Doesn't change the fact that it cannot be interpreted with anything less than lots of computing horsepower."

I addressed this earlier, with regard to just how much computing power was needed.

The use of a simple Excel (or other brand of) spreadsheet allows one to hone in on as many distortion products as one wishes to check, including spcifically for HD, THD, IM, etc. Last time I heard, such a spread sheet will run on just about any computer that is still working!

I also called out the simple expedient of a visual comparison bwtween two DUT's, and to examine the overall level of the visibly displayed distortion products. This requires no more computing power than to run the spectrum analyzer software used with a soundcard, etc. Such programs have become very common and inexpensive, and readily available over the internet.

As for not having a dedicated program, or dedicated hardware or software to specifically provide these things automatically whe making measurements with the Phi Spectral, I am an individual, with limited resources, what I can afford to do or to provide all by myself is not necessarily an inherent limitation of the test method, it should be quite obvious by now that it would not take a programing genius to create such a software program, nor would it take any extraordinarily expensive hardware to implement it. A studio grade (full duplex) sound card should suffice for the hardware, and a simple variation on one of the existing spectrum analyzer packages availabel could easily be made to do the computational dirty work, including automatic distortion product analysis .

As I noted in the paper, this test signal was presented as a concept, one to be explored and to be worked with, and it would not be too difficult to create the necessary standard configuration, create a standard by which it could be made transportable, etc.
You are definitely in the minority if you feel that spectrum analysis can not be made to be acurate and repeatable.

In your post #130:
http://forums.audioreview.com/showpost.php?p=53193&postcount=130

You said:
"Again, I urged you to go look at Steve Eddys comments on this at AA, have you???"

Yes, he should go look, because then he would discover that what Steve Eddy was posting about was primarily his concen over wire movement, and whether or not it would be sufficient to generate significant levels of IM. In typical fashion, he went all over the map, got off on side issues, and generally ignored the content of my replies (much like you attempt to do here), YET NOT ONCE DO I RECALL THAT HE CRITICIZED THE ACTUAL TEST SIGNAL ITSELF, OR THE METHOD BEHIND IT. He was arguing about ONE of my tentative interpretations of the data with regard to ONE of the specific measurements I did using the Phi Spectral test signal.

So put the Steve Eddy train to bed, it is not at all like you are trying to portray it here.

You said:
" My argument isn't that you can't get some results, but whether they are useable, transportable, or can be standardized. And to now, the answer is no."

I have addresed some of the issues with regard to standardization and transportability. These are not insurmountable issues, and could easily be dealt with.

You said:
" Do they reveal anything that can be garnered by more elegant and simple means, no."

I have already addressed this at some length, and shown you to be wrong on this count.
You can post it all you want, but that won't change the facts. In point of fact, the new signal has been used to discover a form of CDP digital filter clipping distortion that occurs on transient signals, or signals with a lot of different frequency components, it has been used to provide a measure of loudspeaker sound quality that was NOT obvious from the traditional HD measurements, and has been used to detect VERY subtle and hard to spot forms of distortion that are all but invisible with the traditional HD and IM methods.

"Go do a Google groups search on Jon Risch and see how he was challenged there by his peers. He no longer posts there, because his theories could not stand up to the scrutiny of his peers."

This is another challenge you hope will go unanswered, because if they look, they will see that who I was challenged by were some of the very worst of the hardcore naysayers, folks who make FLZapped look like a pleasant and reasonable man. Arnie Krueger is notorious for being one of the most illogical, word twisting, unscientific naysayers on the newsgroups.

I quit posting there, because due to SHEER volume of posts (Arnie must do nothing else), the naysayers used enough bandwidth to asure that their POV would always have the last word, always have the last word twist, always take a last pot shot. Kind of reminds me of how this place looked not too long ago, where anyone who posted about cable sonics in the Cable forum would get shouted down by a horde of naysayers.

Let me show you how Jon gets erroneous results.....

First look here:
http://www.geocities.com/jonrisch/page7.htm
Please note Figure X - in particular, the curve labeld "Tweeter" which is green.
Now continue to:
http://www.geocities.com/jonrisch/page8.htm
Jon says this:

"This graph shows the reduction in IM distortion products when using two separate speaker cables to the separated crossover sections of a speaker, otherwise known as bi-wiring, compared to using a single speaker cable. - - - - Only the single cable vs. the tweeter cable is shown here for clarity."
I
So he has his test signal on a "single cable" system(black) is overlayed with the "tweeter cable" signal in a bi-wire set-up(magenta). He claims a reducton in IM, however, if you go back to the first curve, and overlay it with the results curve, what you are getting is NOT a reduction in IM, but just the natural action of that half of the system crossover. You would get the same results on a "single wire" system by going inside the box and connecting to the tweeter side of the crossover.

I explain this at my website, specifically for those who could not grasp that the IM products were NOT following exactly the simple curve of the crossover impedance slope.
See the Analysis section down at the bottom of page 11:
http://www.geocities.com/jonrisch/page11.htm

Besides, if you were to connect the "single wire" to ONLY the tweeter portion of the crossover, you would then be bi-wiring! If you literally meant a connection to the OUTPUT of the crossover, then it has become even clearer that you do not understand what has been written about, and what has been measured.

Please also note that you cannot clearly see the difference between any system generated noise and any generated intermodulation product.(Do you remember what I said about that earlier??)

This is more a problem with your ability to look at and understand what is seen with these graphs, than any inherent limitation or problem with the test signal or the measurements.

On these graphs, ANYTHING on Fig Z that is not a primary tone (which are the primary tones are pretty obvious, in this measurement, they are grouped together in two bands, as shown at page 10 in Fig Y) that is above approx. - 95 dB is definitely a result of a distortion product being displayed by the spectrum analyzer. Due to the use of the current probe, which has a 20 dB signal level penalty compared to a voltage measurement (the output of the current probve is 0.1 volt per 1 amp), I was close to the actual noise floor with these measurements. The measurement system noise was ALL well below -95 dB, but I am being conservative in stating that anything above -95 is quite certainly a distortion product. As with ANY spectrum analysis that is looking at such a wide dynamic range, one must always establish the noise floor baseline, and be sue they are looking at something other than noise. This is true of ANY sort of spectrum analysis, and not just of my test signal or my measurements.

Once again, I clearly point the facts out at my website, and explain why what Bruce says is totally incorrect and once you read the explaination, it becomes obvious where Bruce has gone wrong.

Steve Eddy pretty much made these same observations, including errors in Jon's methodology as he is more familiar with the test equipment being used.

No, actually, he did no such thing. I want to see the exact post referenced where he said this.
He did NOT make these same observations, nor did he point out any errors with my methodology. He argued about wire movement and IM, rather than the actual test signal itself.

These types of fundemental errors is why Jon gets the hell beat out of his theories all the time by his peers.

Bruce, it is these kinds of slanted and untrue statements such as you have made in the last couple of posts, that show why you and so many of the naysayers are more interested in the personalities, rather than the real science involved.

There ARE no "fundamental errors" for me to get beat up over, rather, you and a few others (both now and in the past) have shown that, in fact, it is your failure to comprehend fully that is resulting in YOUR fundamental errors of interpretation. I find it ironic, that you then ascribe these errors on your part, to me. You have done this repeatedly throughout this thread, and yet deny it has happened, instead, acting as if I were the one who was so grossly in error.

It is unfortunate that what is being discussed is as esoteric as it is, because it would be immediately clear to someone familiar with these kinds of audio measurements, that what I am saying is correct, and that your comments are the ones off in left field.

Jon Risch