Audio Note speaker design

[Feanor]

RGA and others,

RGA's passion for Audio Note speakers is very well know and long standing. Apart from RGA's flat assertion that they sound better than anything, there are the eccentric and questionable aspects of AN's designs. It's not fair to dismiss AN models out-of-hand just because they flout industry trends; but neither is it obvious that any one or combination of them automatically suggests an AN superiority in theory.

If everyone, especially RGA, is up for it, I would like to review ANs divergences from popular practice with a view to possibly revealing the AN phenomenon.


Broad (and sharp-edged) baffles:

There is one advantage of a broad baffle the I'm aware of. That is, the gain that occurs when the baffle is wider 1/2 the wave length of the sound; obviously this occurs at a lower frequency with a wider baffle.
On the other hand I have heard it said that the optimal width of the baffle is not much wider than the aforementioned 1/2 wave length. So to the extent that this true, the wider baffle wouldn't favor the AN tweeters even if it assists the mid/bass driver. You'll notice that in some designs, the cabinet is shaped to be narrower around the tweeter than the mid/bass drivers.

Tweeter placement:

AN's practice of placing the tweeter on the vertical axis isn't so much against current practice as against best practice. It is true that response spikes cause by the cabinet's edges are less if the tweeter is placed at different distances from each edge, (right/left/top/bottom). As mentioned above, the shaping of the cabinet around the tweeter in some non-AN designs which will usually reduce defraction. Alternatively, some use a semi-horn or "controlled dispersion" surround for the tweeter; Paradigm designs their grills to control dispersion.

Large mid/bass driver:

The frequency at which a driver will begin to "beam" rather than disperse the sound is 1/2 the wave length at that frequency. Thus an AN 8" mid/base with an effective driver diameter perhaps 6" will begin to beam above around 1100 Hz. The more typical 6.5" driver with an effective 4" width will start to beam around 1700 Hz. Thus AN's 8" and 10" drivers are disadvantaged with respect to dispersion assuming the crossover is, as one would expect, above 1100 Hz.
[edit] Of course, a larger driver will typically go deeper than a smaller driver; it will also play louder versus a single, smaller driver. Vendors today, likely because of narrow baffles, offset the loudness aspect by using multiple, smaller drivers. [/edit]

Under-damped, resonant cabinets:

AN's cabinets are made of plywood, both more resonant but less predictably so than the more common MDF. Contrary to usual practice, which is to reduce resonance as much as possible, AN cabinets are supposedly design to resonate. I guess in theory you could design a cabinet that resonates in such a way as compensate for speaker drive irregularities. However this would seem to require such extremely tight tolerances in both cabinet and driver as to be unachievable in practice.

Near-wall or corner placement:

No doubt placement near-wall, or more so. corner placement will boost bass. Also, it will reduce the need for "baffle shelf compensation" which relates to baffle width effect as discussed above. Thus AN's recommended placement and baffle width both tend to increase efficiency.
I suspect that the near-wall/corner placement must tend to less predicable over-all frequency response and bass humps however. This no doubt the reason most designers today design for placement 1-3" from the wall.

Model differentiation based on crossover components:

There are boutique speaker makers who offer different, optional grades of crossovers, but none to the extent that AN does where a single, basic design can see a several-fold price increase as the supposed quality of the crossover increases. The significance of wire and crossover component quality for sound quality is debatable, (though no doubt better is better), but there is certainly diminishing returns and AN seems to away over the top in this regard.

Thus AN uses a combination of good and dubious practices. The practical success of their approach can be judge only by listening, but on balance what they do doesn't presuppose a superior speaker.

[audio amateur]

Interesting post, Feanor.
I am hoping to have a listen to some this April in Denver during my trip to the US.

[Luvin Da Blues]

INCOMING!!!!!!!!


EVERYBODY DOWN

[blackraven]

I've been hiding in my bomb shelter ever since this post started!

[audio amateur]

LOL, I guess I better hide aswell..

[JohnMichael]

Art Dudley uses a pair in his listening room and that has increased my interest in hearing a pair. I also liked the Snell Type E that one of the models is based on as far as cabinet size and driver compliment.

I remember when Boston Acoustics first began manufacturing speakers they also went with the wide baffles. The A 200's, 150's, 100's and 70's all had a shallow wide baffle. I enjoyed the sounds of the larger models. At the time wide baffled speakers would not work in my room.

Corner placement would not be possible for me now. I have the room for larger speakers but the corners are occupied.

Most of my speakers have the tweeters in vertical axis with the woofers. Offset tweeters with different distances from the edges could be a benefit if the front baffles are mirrored for better imaging. My OML 1's have a chamfered front baffle so the distance from the tweeter and the side edges change. Of course the top edge and bottom edge vary.

Still it would be fun to hear a pair.

[Jimmy C]

...yes, it would seem like common sense to deaden the speaker to the max. My Revels (for eg.) were very inert and heavy (for their size) - almost like doing the "knuckle-wrap" test on a marble floor.

In contrast, you can actually feel the cabinet on my Reynauds flexing a tiny bit... almost like they're allowed to "breathe" with the music. What's ironic is that the M22s seemed to deaden the music as well, while the Twins are more lively.

Bob Neill at Amherst Audio sells Audio Note and JMR, saying they sound completely different, but both (by my understanding) seem to be his favorites.

It's funny how an unassuming (and relatively inexpensive) 2-way box could in many ways be "the best speaker I've heard", but many of today's speakers simply don't sound like music, they don't sound "right". I'm not saying my humble stereo rig does everything the best, it doesn't. Maybe there is something to the Audio Note thing despite counter-intuitive
design principals. I haven't heard them.

Oh - and please... no one ask me for serial numbers for the Revels I had? I sold them... really... :*)

[Ajani]

Oh - and please... no one ask me for serial numbers for the Revels I had? I sold them... really... :*)

Well at least tell us where you bought them, otherwise we're forced to assume that you are a Revel bashing troll

[Jimmy C]

...the A70s were my first decent speaker. My friend recently gave me a pair of near-mint A100s, and that's part of my bedroom rig now. I bit the bullet and bought new replacement woofers from BA. They have sonic problems "fer sure", but they can be quite dynamic and always easy on the ears. I do, however, think I need a smaller stereo in here...

What's odd is Boston decided to do the offset tweeter thing in some of the later series.

The top-dog A400 was the cat's pajamas to me at that time - I wonder how they would stack up now.

Yup - the Snells (same era) were also very good, but out of my price range at the time.

[Jimmy C]

Well at least tell us where you bought them, otherwise we're forced to assume that you are a Revel bashing troll

...I simply don't remember... it's been so long... but it was in a store. They sold speakers, amps, turntables and stuff. Surely, that's enough info to figure out if I'm full of B-E-E-P, right?

Just kiddin', I have fun with the arguments at times... don't we all :*)

Actually, the store was "American Audiophile" in Rockville Center here on Long Island.

Funny... the place is a MESS. Too much gear, not enough space, and the worst demo conditions I have seen - speakers plopped in the (almost) center of the room, but closer to one side wall, playing WAY too loudly. Rediculous.

They used to have a lot of good 2-channel brands, but they now look like they are doing more and more Home Theater. Sad. But hey, one of the most profitiable audio stores in my area (Audio Den) does indeed cater to HT to a large degree - gotta go where the money is I suppose. In their defense, they have nice stereo gear as well. Well back in 1979, when they had a smaller store, it was obviously all 2-chan. Fun stuff. Guess I'm gettin' old!

I can remember being in the front, smaller room (of American Audiophile) and being suprised to see a small pair of Bose there. I thought it a bit odd, and asked the owner why:

"So I can compare and show people how bad they actually are"

[theaudiohobby]

...yes, it would seem like common sense to deaden the speaker to the max. My Revels (for eg.) were very inert and heavy (for their size) - almost like doing the "knuckle-wrap" test on a marble floor.

In contrast, you can actually feel the cabinet on my Reynauds flexing a tiny bit... almost like they're allowed to "breathe" with the music. What's ironic is that the M22s seemed to deaden the music as well, while the Twins are more lively.

Your comments remind of an occasion when I was listening to Ludovico Einaudi's Le Onde, a particularly demanding track started playing, lo and behold some notes acquired some unnatural prominence, looked at my speaker (Cyrus Icons) and the cabinet was vibrating in sympathy with the music. I disliked it and resorted to dampening the cabinet. If I recall the same thing happened when I tried listening to Mahler Symphony No. 5 on the AN K/B, the speaker dissolved into jelly when attempting the finale, though I concede the stands were also partially to blame on that occasion.

IMO, resonant boxes works for certain types of music particularly voice and bowed strings as adds some tonal richness, but fall down badly on piano and full bore orchestral music, where the added resonance can be an annoying distraction to the knowledgeable listener.

The Audio Notes certainly have their fans, but some of the weakness are simply not to my taste Listening to Nina Simone's "Sinnerman" on the ANJ with its aggressive midrange and lean upper bass was particularly painful experience. ANK/B has a less aggressive midrange but there is only so much bass you can get from small sealed cabinet and in my room it sounded bass light.

[JohnMichael]

The Audio Notes certainly have their fans, but some of the weakness are simply not to my taste Listening to Nina Simone's "Sinnerman" on the ANJ with its aggressive midrange and lean upper bass was particularly painful experience. ANK/B has a less aggressive midrange but there is only so much bass you can get from small sealed cabinet and in my room it sounded bass light.

If they can not reproduce Nina Simone's "Sinnerman" or any of my vast collection of Nina on vinyl and cd I just lot interest.

[theaudiohobby]

If they can not reproduce Nina Simone's "Sinnerman" or any of my vast collection of Nina on vinyl and cd I just lot interest.

Nope, I would not do that as I mentioned in another post I know someone who very much likes Audio Note, he had Audio Notes J on order the last time I saw him, his comments were "they play music". However, the key problem for me is that do not play certain music to my satisfaction.

Furthermore, Audio Note have moved to a stiffer mid/bass driver,so one should expect a few improvements, however the resonant box would still remain an issue.

[Feanor]

....
IMO, resonant boxes works for certain types of music particularly voice and bowed strings as adds some tonal richness, but fall down badly on piano and full bore orchestral music, where the added resonance can be an annoying distraction to the knowledgeable listener.
...

This more or less what tubes do on the electronic side, IMO. In both cases it's due to added distortion of one type or the other.

[mlsstl]

Resonant boxes are one solution to the problem of back-waves from the drivers. A number of well regarded speakers use this method. There is also a degree of misunderstanding about the theory of the design. (Full disclosure, I have a set of Spendor SP1/2Es which use this cabinet design. The newer Spendor "S" series don't.))

As the cone oscillates back and forth, the driver creates a back wave of sound that is just as strong as the front wave launched into the room. The question becomes what happens to this energy?

Bass frequencies can be sent through a transmission line or port and actually reinforce bass output. (Or used in an acoustic suspension design to stiffen the compliance of the driver at bass frequencies.) Higher frequencies can be absorbed by the batting or stuffing that is used inside the box. However, there is a middle and lower range of frequencies that aren't well absorbed by the speaker stuffing.

If not handled in some fashion, they can re-radiate though the driver cone. However, they'll be out of time with the front launched wave and this can smear the sound. The ear is particularly sensitive in this frequency range.

The goal of a cabinet that flexes a bit is rather like crash crumple zones in car design. Rather than transmit 100% of the impact into the passenger compartment, the goal is to use up a lot of that energy by bending metal.

By having a speaker wall that flexes, the internal pressure wave is partially dissipated in flexing the cabinet walls. Part two of the design is to have a heavy coating on the interior cabinet wall to dampen the panel at the frequencies where the ear is most sensitive. This helps the exterior of the panel reduce what it radiates into the listening room.

Of course, there are other approaches for how to dissipate the rear wave, but it is an issue that all designers have to face. Simply having a cabinet that is so stiff that it sounds dead when you rap it does nothing by itself to get rid of that midrange energy. And you have to be careful in deadening the driver cone to prevent the back wave from passing through as this can adversely affect the driver's other performance factors.

Like many engineering problems, there are multiple ways to address it. Each has their advantages and disadvantages. However, there are some marvelous sounding speakers that use the thin-wall BBC type design, and they are all highly regarded for their clarity in the reproduction of the human voice. It works for me.

[Feanor]

Thanks, misstl,

These are the sort of comments I was hoping to evoke from members. Clear the flexible, resonant cabinet is a completely different approach from the very rigid with lots of internal stuffing. Are Harbeth speakers of the "thin walled" type? They certainly have a great reputation.

What I wonder is which speaker design is likely to produce the more predictable, less problematic result for the DIY speaker designer? I suspect that rigid cabinet design will be freer from anomalies -- that is, more likely to work the first time without a lot of testing or experimentation.

Resonant boxes are one solution to the problem of back-waves from the drivers. A number of well regarded speakers use this method. There is also a degree of misunderstanding about the theory of the design. (Full disclosure, I have a set of Spendor SP1/2Es which use this cabinet design. The newer Spendor "S" series don't.))

As the cone oscillates back and forth, the driver creates a back wave of sound that is just as strong as the front wave launched into the room. The question becomes what happens to this energy?

Bass frequencies can be sent through a transmission line or port and actually reinforce bass output. (Or used in an acoustic suspension design to stiffen the compliance of the driver at bass frequencies.) Higher frequencies can be absorbed by the batting or stuffing that is used inside the box. However, there is a middle and lower range of frequencies that aren't well absorbed by the speaker stuffing.

If not handled in some fashion, they can re-radiate though the driver cone. However, they'll be out of time with the front launched wave and this can smear the sound. The ear is particularly sensitive in this frequency range.

The goal of a cabinet that flexes a bit is rather like crash crumple zones in car design. Rather than transmit 100% of the impact into the passenger compartment, the goal is to use up a lot of that energy by bending metal.

By having a speaker wall that flexes, the internal pressure wave is partially dissipated in flexing the cabinet walls. Part two of the design is to have a heavy coating on the interior cabinet wall to dampen the panel at the frequencies where the ear is most sensitive. This helps the exterior of the panel reduce what it radiates into the listening room.

Of course, there are other approaches for how to dissipate the rear wave, but it is an issue that all designers have to face. Simply having a cabinet that is so stiff that it sounds dead when you rap it does nothing by itself to get rid of that midrange energy. And you have to be careful in deadening the driver cone to prevent the back wave from passing through as this can adversely affect the driver's other performance factors.

Like many engineering problems, there are multiple ways to address it. Each has their advantages and disadvantages. However, there are some marvelous sounding speakers that use the thin-wall BBC type design, and they are all highly regarded for their clarity in the reproduction of the human voice. It works for me.

[mlsstl]

Feanor, yes, Harbeth's use the thin wall BBC design.

[Feanor]

Folks,

I suppose that some might think my purpose here is to bait RGA. Well, no ... at least not primarily.

My retirement is fast approaching and a project I'd like to try when I have a bit more time is building a pair of DIY speakers suitable for a smaller room that can't accomodate my Magneplanar MG 1.6. That room is no bigger than 10' x 16' -- on the large side of small.

In this context near-wall or corner design becomes a practical, or even necessary, approach. And given near unavoidability of a box, non-dipole design, the other design issues I listed become very relevant. What I'm contemplating is a high-precision, two-way design, probably supplement by a small subwoofer such as my present PSB Subsonic 5.

Naively maybe, I believe that I can duplicate for $1000 - $1200, and using a conservative design approach, the capabilities of popular monitors costing twice as much. I'm leaning to closed-box with quality tweeter that can handle a relatively low, 1200 - 1500 Hz, high-pass filter.

[Florian]

How about some SET amps and a pair of Klipsch Cornwalls........ boooom

[Luvin Da Blues]

[QUOTE=Feanor]Folks,

I suppose that some might think my purpose here is to bait RGA. Well, no ... at least not primarily. [QUOTE]

Just my feable attempt at humor.

[theaudiohobby]

Feanor, yes, Harbeth's use the thin wall BBC design.

BBC is a radio TV broadcaster and given the age of the original design(60's) and BBC interest in the spoken speach, going for a thin wall design seems entirely a plausible trade-off it, the inherent distortion plays well to speach.. I gather that in the 70s, Decca and EMI auditioned a variety of speakers and selected B&W801 as their preferred studio monitor for classical music. So it's horses for courses, really, the job at hand dictates the acceptable trade-offs..

[mlsstl]

the inherent distortion plays well to speach

There is certainly room for a lot of opinions, but your comment suggests that the goal was to add distortion, albeit a pleasant one. That implies that there would be no distortion with a thick walled design. That is not a given.

If you look at the explanation above, ALL speaker drivers generate both a front wave and a rear wave from the cone's back & forth oscillation. That rear wave does not simply disappear on its own, either because you used a stiff cabinet or waved a magic wand. In fact, a stiff cabinet design (one that gives a dull response to a knuckle rap) can aggravate the problem if it simply acts as a bumper to bounce energy back.

The question for all speaker designers (at least the ones who care to address it), what do we do with the energy inside the cabinet? It has to be used somehow in order to keep it from re-radiating through the cone into the listening room. Box stuffing, regardless of type, is great for absorbing this energy as the frequency goes up, but it is not very effective at lower midrange frequencies.

By dissipating the energy in a controlled fashion, in a good implementation of the thin wall design, the distortion caused by rear wave re-emerging into the listening room is actually reduced, not increased.

And the design hardly ceased development after the introduction in the 1960s. Spendor just released their "R" series with improvements in cabinet materials and design and Harbeth also continues to use the method in their highly regarded speakers. You might as well accuse the horn speaker builders of having made no design improvements since the Voice of the Theatre speakers were introduced. Or claim that modern pulp/paper cones are no longer suitable since they were broadly introduced in the 1920s.

As for the BBC, don't forget they have the only professional chamber choir in the UK (established 1924), the BBC Philharmonic (established 1922) plus four other full orchestras. They probably know a few things about recording music, as well as voice. ;-)

[theaudiohobby]

There is certainly room for a lot of opinions, but your comment suggests that the goal was to add distortion, albeit a pleasant one.

Nah, that was not my intention,.the goal of the speaker was not add distortion but the dissipate driver rear-wave effectively, a thin-walled speaker by definition will have stronger resonant mode(s) and at a higher frequency than a near inert box, the goal is to ensure that those resonant modes are benign.

By dissipating the energy in a controlled fashion, in a good implementation of the thin wall design, the distortion caused by rear wave re-emerging into the listening room is actually reduced, not increased.

Therein lies the rub, dissipation is not fully controlled around the resonant modes. The trade-off is to tune the walls so that the resonant modes occur at a frequency and an amplitude that has the least negative impact on the speaker.

[mlsstl]

The trade-off is....

Aye, there's the rub. And that applies to all speaker design options. Take anyone's favorite speaker and there will be trade offs, no matter how expensive or fancy. The trick for a listener is to discover which speaker compromises in areas that he doesn't place at high priority.

[Ajani]

Aye, there's the rub. And that applies to all speaker design options. Take anyone's favorite speaker and there will be trade offs, no matter how expensive or fancy. The trick for a listener is to discover which speaker compromises in areas that he doesn't place at high priority.

That, IMO, is the main problem with looking at speaker technology... different designs all have their advantages and disadvantages.... Is Panel Tech better than Box? Depends on what your sonic goals are and how much money you have to spend... A panel is arguably the cheapest way to achieve midrange bliss, but is a very expensive way to get dynamic range, while a box is probably the cheapest way to get proper dynamic range.... Is it better to use the exact same material for all of the drivers (Tweeter to Bass) like Revel or to use a different material for each section like B&W? The Revel design gives consistency and cohesion across the entire frequency range, while the B&W design trades consistency for trying to apply the best material for each section of the frequency range...