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  1. #1
    Veg-O-Matic ToddB's Avatar
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    Jon Risch distortion test signal

    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

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    And you people thought I'd never post in this forum. Silly rabbits.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

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    Suspended markw's Avatar
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    Let's wait and see what the AES has to say about it. After all, they have more knowledge and experience than most of us here. They want scientific evidence.

    Remember cold fusion? Everyone wanted it, so...

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    Veg-O-Matic ToddB's Avatar
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    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. 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.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

  4. #4
    Color me gone... Resident Loser's Avatar
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    Well la-de-da Todd...

    ...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...)

  5. #5
    Forum Regular Monstrous Mike's Avatar
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    Alright, I'll bite....

    Quote Originally Posted by ToddB
    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. 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?
    Friends help friends move,
    Good friends help friends move bodies....

  6. #6
    Suspended markw's Avatar
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    Are you a doctor?

    Quote Originally Posted by ToddB
    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. 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.
    Last edited by markw; 08-30-2004 at 03:17 PM.

  7. #7
    Forum Regular gonefishin's Avatar
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    Quote Originally Posted by ToddB
    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. 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.

    5. No trolling.

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    ok...maybe ya ain't quite trolling...but your certainly trying to stir the pot.
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  8. #8
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by ToddB
    ...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

  9. #9
    Forum Regular FLZapped's Avatar
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    Quote Originally Posted by ToddB
    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

  10. #10
    Forum Regular Swerd's Avatar
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    Quote Originally Posted by E-Stat
    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.

  11. #11
    Forum Regular Swerd's Avatar
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    Quote Originally Posted by ToddB
    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

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    This was presented at the annual AES meeting in 1998. See http://www.aes.org/publications/prep...nts_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.
    Last edited by Swerd; 09-01-2004 at 07:58 AM. Reason: typo

  12. #12
    Suspended markw's Avatar
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    So, in essense, it is just his unproven opinion....

    ...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.

  13. #13
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Swerd
    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

  14. #14
    Forum Regular Swerd's Avatar
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    Quote Originally Posted by E-Stat
    …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.

  15. #15
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Swerd
    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

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    Reply To Resident Loser

    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.

    Quote Originally Posted by Resident Loser
    .
    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.

    Quote Originally Posted by Resident Loser
    .
    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.).

    Quote Originally Posted by Resident Loser
    .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.

    Quote Originally Posted by Resident Loser
    "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)

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    Reply to markw and Swerd

    Quote Originally Posted by markw
    ...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

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    Reply to FLZapped

    Quote Originally Posted by FLZapped
    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.

    Quote Originally Posted by FLZapped
    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.

    Quote Originally Posted by FLZapped
    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.


    Quote Originally Posted by FLZapped
    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

  19. #19
    Veg-O-Matic ToddB's Avatar
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    Quote Originally Posted by Resident Loser
    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.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

  20. #20
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    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
    Sir Terrence

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  21. #21
    Veg-O-Matic ToddB's Avatar
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    Quote Originally Posted by Monstrous Mike
    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.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

  22. #22
    Forum Regular FLZapped's Avatar
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    Quote Originally Posted by J Risch
    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/...410-00257a.pdf

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

    http://hyperphysics.phy-astr.gsu.edu...io/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

  23. #23
    Veg-O-Matic ToddB's Avatar
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    Quote Originally Posted by E-Stat
    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.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

  24. #24
    Veg-O-Matic ToddB's Avatar
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    Quote Originally Posted by Swerd
    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.
    "Reality supercedes science."
    -- badman, 9/3/02, AudioAsylum.com

  25. #25
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    Quote Originally Posted by ToddB
    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..

    Quote Originally Posted by Sir Terrence the Terrible
    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

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