In praise of AR3a's

[genek]

AR's "Acoustic Power Output," on the other hand, is measured in a reverberant chamber and represents an integrated summation of both direct and reflected response therein, masking the true direct response.

You say this as if it's some sort of revelation. Villchur told us all of this over 40 years ago. As far as he was concerned, the combination of direct and reflected response was the "true response" of the speaker, not its direct response, because the speaker was designed to perform in AR's concept of a typical listener's environment rather than in an anechoic chamber.

http://www.classicspeakerpages.net/library...esting_and_mea/

Villchur also provided guidance for users on how to set up their speakers and their listening environment to best reproduce the conditions the speakers were designed for:

http://www.classicspeakerpages.net/library...e_most_from_yo/

(Be prepared for some eyestrain from the low-res scans)

This may be new info for some of the folks on AK, but I think it's pretty much ancient history around here.

[tysontom]

Key to the Toole perspective is that we do not listen in the reverberant field, nor even a uniformly reflective one, either, which is the cornerstone of AR's "Max dispersion" designs.

They measure poorly both on- and off-axis, as Allison disclosed in a 1970 AES paper*, in which he argued that the energy was going SOMEWHERE in the room, and if it is measured at enough locations, it sums to a uniform response.

Toole has effectively demonstrated that measured response, both on-axis and over a narrow listening window, correlates highly with listening preferences, instead:

http://www.aes.org/e-lib/download.cfm?ID=1...amp;name=harman

*Presented October 12, 1970, at the 39th convention of the Audio Engineering Society, New York, and published in the AES Loudspeakers anthology Volume 1, p. 258, as "The Sound Field in Home Listening Rooms"

Zilch,

It is interesting how you have gone out of your way to criticize the AR and Allison wide-dispersion approach to speaker design, throwing in a lot of Floyd Toole’s quotes along the way, hitching your wagon to everything he has to say. In my opinion, Dr. Toole (now retired) is/was a bright and accomplished researcher-writer in the audio field, but with no real contribution in the field of loudspeaker development and design. Moreover, he has no noteworthy loudspeaker designs whatsoever that will ever be remembered in the annals of audio history. What did he ever invent? He wrote voluminously and was on the JBL payroll for several years, but I suspect he probably had a commercial “ax to grind,” criticizing those loudspeaker pioneers who did actually contribute to the loudspeaker state-of-the-art over the years such as, for example, Edgar Villchur, Amar Bose, Henry Kloss and Roy Allison. So Toole he stood back, smugly, and criticized designs -- such as the AR-3 -- that actually did make a huge contribution to the science of accurate-sound reproduction, rather than consider the true merits of Villchur designs. Did he say anything about the dome tweeters? No, he praised the AR-3 for its acoustic-suspension woofer, which is somewhat irrelevant and was actually developed several years earlier in the AR-1. He criticized the live-vs.-recorded concerts, lumping in the AR concerts with the Olson and Briggs demonstrations, the latter two which were actually audio “demonstrations,” not true live-vs.-recorded concerts. I doubt he ever witnessed any of those events, relying only on some various reports he mentions. There are many published reports that people listening to the AR concerts (there were over 75 of them) were simply unable to detect the switchovers, and these listeners ranged from music critics to engineers to general music-lovers. There were some very discerning listeners at those concerts, not some wild-eyed people listening to Edison’s first talking-machine public demonstration. There have been criticisms about the AR LVR concerts for many years, but has anyone ever managed to equal it? Do you know of any live-vs.-recorded event, comparing live instruments to reproduced sound that has ever been done successfully other than the AR-3 concerts? Since this basically hasn’t occurred either before or since those events, the tendency has been to criticize the viability and methodology of these concerts. Yet Toole’s criticism is so vague that in his new book, Sound Reproduction Loudspeakers and Rooms, he actually has the AR-3 and the AR-3a confused.

Oh yes, Toole does not think we listen in the reverberant field when listening at home. Unlike the large symphony hall, for example, rooms have very different reverberation times, greater absorption etc. This is undoubtedly true for many rooms -- especially small ones -- but large rooms with relatively reflective surfaces reflect a lot of energy. Toole’s conclusions, which dismiss this concept of reverberant sound field out of hand, tend to disagree with the findings of Leo Beranek, Fred Hunt and Olson, as well as the conclusions of many speaker designers, that much (in fact most) of what you hear well back in a room is reverberant energy. Most of Toole’s loudspeaker evaluations in Canada had the speakers out away from the front wall, and the listeners up closer to the speakers. In this regard, certainly, there is a lot of direct, first-arrival energy reaching the listener. Good “imaging,” as you would have it. Why don’t you just strap on a good pair of headphones? Get a good pair of Etymotic ear-canal earphones and stop wasting your money on thos "imaging" loudspeakers. Yes, the headphone/earphone thing is a sort of binaural experience, but it puts you right in there on the front row, if not on top of the orchestra, if that is what you want to hear.

--Tom Tyson

[Zilch]

You say this as if it's some sort of revelation. Villchur told us all of this over 40 years ago. As far as he was concerned, the combination of direct and reflected response was the "true response" of the speaker, not its direct response, because the speaker was designed to perform in AR's concept of a typical listener's environment rather than in an anechoic chamber.

This may be new info for some of the folks on AK, but I think it's pretty much ancient history around here.

No, the "news" is how they measure according to what has been industry standard methodology for 50 years, the difference being that we can now do it ourselves without an anechoic chamber, and it's clear why AR didn't publish the direct response.

The issue, if it may be suggested there is one, is whether Villchur's concept of "true response" is valid under typical listening conditions wherein:

1) The environment is not a reverberant chamber,

2) Beranek's soundfield theory is inadequate, and direct soundfield dominates the reverberant, and,

3) the reflections are not isotropic, and the soundfield is not diffuse.

[Zilch]

It is interesting how you have gone out of your way to criticize the AR and Allison wide-dispersion approach to speaker design, throwing in a lot of Floyd Toole’s quotes along the way, hitching your wagon to everything he has to say.

Let's not pretend that Toole made all of this up himself. In my view, his primary contribution as researcher may be found in the compilation of the diverse body of knowledge in this field and synthesis of a coordinated perspective, a theory, as it were, of how loudspeakers and rooms behave in combination, which theory now dominates loudspeaker design.

Let's also not pretend that the pioneering proponents of the max dispersion design approach did not themselves have a commercial interest at the fundamental core of their theories and endeavors. Fact is, their design objectives are now all but trivial to accomplish using modern technology, without anomalous artifacts in the direct response, yet only only one purveyor of significance survives in the marketplace today, and it's no coincidence that they do not publish system frequency response data, either.

There's no denying that many listeners are well satisfied with "direct-reflecting" designs, but it's certainly a stretch to attribute this to any superiority of sound reproduction inherent in the concept....

[genek]

No, the "news" is how they measure according to what has been industry standard methodology for 50 years, the difference being that we can now do it ourselves without an anechoic chamber, and it's clear why AR didn't publish the direct response.

The issue, if it may be suggested there is one, is whether Villchur's concept of "true response" is valid under typical listening conditions wherein:

1) The environment is not a reverberant chamber,

2) Beranek's soundfield theory is inadequate, and direct soundfield dominates the reverberant, and,

3) the reflections are not isotropic, and the soundfield is not diffuse.

This isn't "news" at all. AR speakers violated most "industry standards" from the day they were introduced. The company devised its own standards.

Frankly, I find this "issue" as you define it to be about 40 years too late to be of much interest. We are talking about vintage relics, not anything that anyone is actually contemplating putting into production or offering for sale today and therefore has a need to explain or justify to potential reviewers or customers. It's not as if Edgar Villchur is expending any time or energy today trying to convince anyone that his approach to loudspeaker design was valid, is it?

At this time, long after the end of classic AR speakers' life cycles as commercially viable mass market products, the "issues" that are of greatest interest to me (and I suspect to most others around here) are:

1) Can whatever made/makes classic AR speakers sound the way they did/do be identified?

2) If whatever it was/is can be identified, can it be reliably measured?

3) Can the performance of classic AR speakers as they survive today be compared to data collected on the same models when new to determine what performance deterioration, if any, has occurred over time?

4) Can alternatives to no-longer-available original parts be found, created or modified to restore or reproduce original performance in surviving units that have failed or suffered performance deterioration?

How the speakers compare/d to "industry standard methodology" is of minor historical interest only because it helps determine the extent to which their success in their time and their continued appeal today were/are the result of their designers following an iconoclastic path. The success and the appeal are established facts and not subject to debate.

[Zilch]

How the speakers compare/d to "industry standard methodology" is of minor historical interest only because it helps determine the extent to which their success in their time and their continued appeal today were/are the result of their designers following an iconoclastic path. The success and the appeal are unquestionable facts.

I believe that's what we're discussing, and I'm not seeing a disconnect here, to wit:

1) Can whatever made/makes classic AR speakers sound the way they did/do be identified?

That begins with the design philosophy: max dispersion and how that interacts with rooms.

2) If whatever it was/is can be identified, can it be reliably measured?

Of course.

3) Can the performance of classic AR speakers as they survive today be compared to data collected on the same models when new to determine what performance deterioration, if any, has occurred over time?

I just did that for AR3a. Compare to the 1970 Allison data.

4) Can alternatives to no-longer-available original parts be found, created or modified to restore or reproduce original performance in surviving units that have failed or suffered performance deterioration?

Well, sure, all that is required is a commitment to do it; we've had this discussion in another thread here....

[tysontom]

Let's not pretend that Toole made all of this up himself. In my view, his primary contribution as researcher may be found in the compilation of the diverse body of knowledge in this field and synthesis of a coordinated perspective, a theory, as it were, of how loudspeakers and rooms behave in combination, which theory now dominates loudspeaker design.

Let's also not pretend that the pioneering proponents of the max dispersion design approach did not themselves have a commercial interest at the fundamental core of their theories and endeavors. Fact is, their design objectives are now all but trivial to accomplish using modern technology, without anomalous artifacts in the direct response, yet only only one purveyor of significance survives in the marketplace today, and it's no coincidence that they do not publish system frequency response data, either.

There's no denying that many listeners are well satisfied with "direct-reflecting" designs, but it's certainly a stretch to attribute this to any superiority of sound reproduction inherent in the concept....

Zilch,

Toole was an accomplished writer and researcher, no doubt. However, some of his details are slip-shod, in my opinion, as I pointed out in my last post, which leads me to ponder if some other details in his new book are probably lacking in scientific rigor and accuracy. You can’t just say what you please without proper documentation, and throughout his book he provides prolific references -- yet his AR information was completely lacking in accuracy. Even the frequency-response curve on the AR-3, probably done in the early 70s, is meaningless. The curve is replete with all sorts of interference effects, improper boundary loading and so forth. It appears to be a 4π anechoic measurement, showing a continuous downward slope from about 500 Hz down to 200 Hz, at which frequency the cabinet is effectively a 2π baffle, and below that frequency the response follows the usual slope. It makes it appear as though the speaker was sadly deficient in bass output. The response curve also has very little correlation with the speaker’s actual sound unless you listen 1 meter in front of the speaker. That curve, dismissive by Toole, was described as, “The central issue with this product (the AR-3) is its frequency response, which significantly rolls off at both the low and high frequencies.” He remarked that low frequency would be aided by boundaries, but did not elaborate, leaving the reader with the impression that the AR-3 was probably deficient in the low bass. What he actually missed is that the AR-3 woofer is flat within ± 1.5 dB from 38-1000, when radiating into 2π steradians, facing into anechoic space (It also about that flat when “close-miked”). Why wouldn’t he remark about this? Do we listen to loudspeakers suspended from a rope in the middle of a room? That is the anechoic 4π perspective. That early AR test performance -- repeatable by anyone, anywhere -- was apparently unknown by him at the time. I believe we’ll be seeing a revised edition of his book published soon.

Do you think that most good inventions come about because of “commercial” interests? Maybe that’s the JBL perspective, but most of the real scientific advancements come about because someone is investigating a problem, not just looking for a way to make money. Villchur had no loudspeaker company when he researched the acoustic-suspension design. He didn’t want to build the speaker, and he tried to sell his paten for a nominal amount of money, but he had no takers and ultimately did go into business to build the design. It wasn’t “commercial” to start with, however.

--Tom Tyson

[Mexicomike]

I gotta ask, despite this subject being totally beyond me from a science point of view:

These folks that "prove" various AR speakers were deficient in bass and treble - did they ever LISTEN to the speakers? Sounds like the answer would be "No."

[Zilch]

Toole was an accomplished writer and researcher, no doubt. However, some of his details are slip-shod, in my opinion, as I pointed out in my last post, which leads me to ponder if some other details in his new book are probably lacking in scientific rigor and accuracy.

Here, you mean?

Toole’s conclusions, which dismiss this concept of reverberant sound field out of hand, tend to disagree with the findings of Leo Beranek, Fred Hunt and Olson, as well as the conclusions of many speaker designers, that much (in fact most) of what you hear well back in a room is reverberant energy.

If you check in the link I provided, Toole himself researched the nature of what he describes as the "transitional" soundfield and presents his findings there, namely, that the Beranek model does not translate to small room listening spaces; SPL instead continues to decline at 3 dB/octave, and there is no reverberant steady state in evidence, rather, late reflections simply decay, instead.

You can’t just say what you please without proper documentation, and throughout his book he provides prolific references -- yet his AR information was completely lacking in accuracy. Even the frequency-response curve on the AR-3, probably done in the early 70s, is meaningless. The curve is replete with all sorts of interference effects, improper boundary loading and so forth. It appears to be a 4π anechoic measurement, showing a continuous downward slope from about 500 Hz down to 200 Hz, at which frequency the cabinet is effectively a 2π baffle, and below that frequency the response follows the usual slope.

I have not yet seen the curve Toole published, but those generated anechoically by AR under both 2- and 4-Pi conditions are shown in the Allison paper, and I have presented a "close-miked" (~1/4") nearfield measurement in my AR3A measurements thread, as well, which represents 2-Pi performance, and it is far from flat.

AR's recommended placement for AR3a was 1-Pi, as I recall, and it's easily seen that bass response in freespace, the "Audiophile" alignment in which speakers are more commonly deployed today, might indeed be considered "shy."

[genek]

I believe that's what we're discussing, and I'm not seeing a disconnect here

I think it's more of a descriptive vs technical disconnect. When you measure response and say that there's rolloff at certain frequencies, there's no issue there, nor is there an issue with saying that the response measured runs contrary to contemporary industry standards for loudspeaker design. I think most people here could have told you both these things before you ever started measuring, though maybe not at what frequencies or by how many db.

The "disconnect" comes when people start applying descriptions such as "bad" or "deficient" to the measurements without adding the qualification "by contemporary standards." I think most people here could also have told you that classic ARs do not conform to "contemporary standards" for loudspeaker design. If they sounded like things we could buy new, a lot of us might be listening to new speakers instead of hanging out here.

[Zilch]

I gotta ask, despite this subject being totally beyond me from a science point of view:

These folks that "prove" various AR speakers were deficient in bass and treble - did they ever LISTEN to the speakers? Sounds like the answer would be "No."

Believe that if you like, but in fact, measurers listen more, and more critically, than typical listeners do, with more precision.

OH, and it's NOT in anechoic chambers, either, BTW....

That's three turds lobbed over the wall thus far, but we're kinda used to it, actually. Read up here:

http://www.zaphaudio.com/evaluation.html

It's Allison who contends the HF is rolled off in the reverberant field to replicate the concert hall response spectrum; I measure and listen in the direct field, and don't find that to be the case, at least not with the pair under study here. They could use a little boost in the VHF, perhaps, as other listeners frequently observe, but I suspect, like me, you are hearing the direct field response....

The "disconnect" comes when people start applying descriptions such as "bad" or "deficient" to the measurements without adding the qualification "by contemporary standards." I think most people here could also have told you that classic ARs do not conform to "contemporary standards" for loudspeaker design. If they sounded like things we could buy new, a lot of us might be listening to new speakers instead of hanging out here.

That's where I often get into difficulty with this. People feel I'm telling them what to like and not, and they take it personally.

It's not about that, and as an investigator, I don't give a whit what anybody else likes or doesn't. This is about finding out what's up, and preferences relate primarily to the listener alone; they do not define the speaker. If someone likes AR3as, that's more specifically about them and their particular listening tastes than about AR3as....

[RoyC]

Take it up with the engineers doing the recording; their job is to capture the ambience of the hall. If they're successful, it's far better not having the room messing with that.

Yeah, like nobody uses constant directivity for live sound reinforcement.

You need to get out more, really, and speculate less.

Spend $168 to build EconoWave and find out. You can even use AR3as for the woofers:

http://www.audiokarma.org/forums/showthread.php?t=150939

Just some perspective...

Having a fair amount of experience with sound reinforcement, I can safely say that the use of horn loaded speakers for that purpose is not a credible endorsement for their use at home. Horns are used in PA speakers primarily for high efficiency and projection. The directivity aspect helps isolate the sound from microphones to control feedback issues. Having listened to a number of these types of speakers in small rooms, my impression at the time was that they were rather unpleasant with recorded music. (Obviously the taming of these beasts for home use is part of of this discussion...so I am not passing judgment on Geddes's products or the "EWave"). In very small venues we opted for Bose 802's (a professional model...similar to the 901, but no rear firing drivers) to get around the annoying nature of the "horns". It should also be noted that the response of virtually all PA speakers is typically tailored by a variety of equalization and "effects" devices...not to mention that they are often accompanied by dedicated "bass" bins. Certainly the nature of "sound reinforcement" has changed the definition and/or description of the "sound" of concerts. Frankly, I have attended many concerts the sound of which I would not want to bring home, not because the hall or venue had "bad" acoustics, but because the amplification of the sound was terrible. There is a noted music hall near my residence which is historically known for its "acoustics". One would never know this fact once the "sound reinforcement" system is cranked up.

I have also spent a fair amount of time in recording studios, and the fact of the matter is that most of the final sound today is mixed down through headphones. Monitor speakers vary in type and placement, and can suffer many of the same issues discussed in this thread. In the early days it was not uncommon to use a consumer loudspeaker as the "mix down" monitor which would impart its own character on the final product. When layering/multi-tracking, sophisticated effects and headphone use became the norm, the "acoustics" of the recording space and associated monitor speakers became much less relevant.

So questions are raised...How do we define the actual goal for the home reproduction of sound? Is it to sound "like" a concert? What concert? Is it to sound like a musical recording was intended to sound? How do we know what was intended? Is the goal to sound like an IMAX theater? What listening volume levels are really the most important? Is it to precisely replicate the sound of an acoustic instrument when most folks have never heard an unamplified acoustic instrument in an ideal setting? Maybe an investment in headphones is in order for some...but given today's vast resources and availability of sound reproduction devices, including restored "classic" speakers, I believe a large variety of very different and very satisfying results can be achieved in a home without the need to proclaim superiority over the rest. It still largely comes down to individual preferences. Measurements are tools, just as consensus of opinions are.

With the above in mind, Zilch, I have read your links, and did some internet searches to seek some opinions on Geddes' speakers. While nothing has convinced me to destroy a pair of 3as for the cause, anymore than I would dismantle a vintage car in hopes of making it go faster...I DO have a pair of extremely nasty AR-2ax cabinets and spare 2ax woofers available. Since you took the time to measure the 3a and my pot replacement idea, I will take the time to listen to your home-friendly horn speaker. I have all the parts with the exception of the compression tweeter and JBL horn...My first question is, although you vary the woofer crossover by impedance, it appears to be rather generic. Since a woofer's inductance can have a significant effect on midrange response, I assume the woofer to horn crossover must be tweaked accordingly. Also, it appears Geddes' design is dependent on a (patented!!!) hunk of foam that gets placed in the horn to help calm it down. Is that incorporated into the E-Wave design?

...PM me with details if you wish. I don't want to hijack this thread with construction details.

Roy

PS I do find it interesting that Geddes bad mouths Asian drivers, prefers to use inexpensive department store electronics, yet keeps the crossover components separated with solderless connections for sonic reasons...Hmmm...

[Mexicomike]

OK, as I said, way over my head.

I'll just leave it at this - My LSTs outperform any other speaker I have owned, including some in the 10k price range - Nestorovic 5AS. Do the LSTs measure as well or better? I have no idea. But they sound more "like music really sounds." Isn't that the point, to sound like things sound?

[genek]

AR's recommended placement for AR3a was 1-Pi, as I recall, and it's easily seen that bass response in freespace, the "Audiophile" alignment in which speakers are more commonly deployed today, might indeed be considered "shy."

Most of AR's literature of the classic period depicts the 3 series (actually, just about all the classic models), either vertically or laying on their sides, at a height that places the tweeter at ear level to the listener, either in bookshelves or on various types of credenzas. Placement in corners and/or on the floor is recommended for "more bass."

AR's brochure for its stands that support the 3, 5 and 2 series in vertical placement several inches off the floor say that the stands should be used when it is not practical to place the speakers "optimally."

Vertical placement on stands or floor seem to have become the default in the ADD series that followed the classic models in the mid-70's.

[Zilch]

So questions are raised...How do we define the actual goal for the home reproduction of sound? Is it to sound "like" a concert? What concert? Is it to sound like a musical recording was intended to sound? How do we know what was intended? Is the goal to sound like an IMAX theater? What listening volume levels are really the most important? Is it to precisely replicate the sound of an acoustic instrument when most folks have never heard an unamplified acoustic instrument in an ideal setting? Maybe an investment in headphones is in order for some...but given today's vast resources and availability of sound reproduction devices, including restored "classic" speakers, I believe a large variety of very different and very satisfying results can be achieved in a home without the need to proclaim superiority over the rest. It still largely comes down to individual preferences. Measurements are tools, just as consensus of opinions are.

You've certainly defined the larger issues there. What we're listening for may be more definitive of our preferences than what we listen to.

With the above in mind, Zilch, I have read your links, and did some internet searches to seek some opinions on Geddes' speakers. While nothing has convinced me to destroy a pair of 3as for the cause, anymore than I would dismantle a vintage car in hopes of making it go faster...I DO have a pair of extremely nasty AR-2ax cabinets and spare 2ax woofers available. Since you took the time to measure the 3a and my pot replacement idea, I will take the time to listen to your home-friendly horn speaker. I have all the parts with the exception of the compression tweeter and JBL horn...My first question is, although you vary the woofer crossover by impedance, it appears to be rather generic. Since a woofer's inductance can have a significant effect on midrange response, I assume the woofer to horn crossover must be tweaked accordingly. Also, it appears Geddes' design is dependent on a (patented!!!) hunk of foam that gets placed in the horn to help calm it down. Is that incorporated into the E-Wave design?

Thank you, Roy; I look forward to your evaluation. As other readers may be interested, I'll answer here, with their indulgence:

Optimally, the lowpass filter should be tweaked for each design. We provide a generic "starting point" so everyone can hear what E'Wave is about and decide for themselves how worthy of pursuit that might be for them in particular, and how much refinement might be desired or warranted, i.e., Zobel or no, etc.. I have myself built with AR2as, and with a bit of BSC, they are fully capable of rocking the house.

No one has gone the "full Monte" with the Geddes foam plug. I consider that a potential enhancement, and not an essential element of the basic design. Sculpting it to fit the waveguide seems, well, "challenging."

Indeed, Geddes is a quirky guy, but certainly knowledgeable and informative. Also, kinda fun, once past his, uhmm, persona....

[tysontom]

Here, you mean?

If you check in the link I provided, Toole himself researched the nature of what he describes as the "transitional" soundfield and presents his findings there, namely, that the Beranek model does not translate to small room listening spaces; SPL instead continues to decline at 3 dB/octave, and there is no reverberant steady state in evidence, rather, late reflections simply decay, instead.

I have not yet seen the curve Toole published, but those generated anechoically by AR under both 2- and 4-Pi conditions are shown in the Allison paper, and I have presented a "close-miked" (~1/4") nearfield measurement in my AR3A measurements thread, as well, which represents 2-Pi performance, and it is far from flat.

AR's recommended placement for AR3a was 1-Pi, as I recall, and it's easily seen that bass response in freespace, the "Audiophile" alignment in which speakers are more commonly deployed today, might indeed be considered "shy."

Zilch,

Toole’s “findings” are not universally accepted as the last word. Those are his interpretations. I frankly put more credence in the likes of Beranek and Hunt (even Amar Bose, for that matter) any day than Floyd Toole. Believe what you wish, but we listen in a predominantly reverberant field in any “normal” listening room -- certainly not totally reverberant, of course, but much more reverberant by far than listening in the direct field. The notion that you are hearing predominantly direct energy if you are well back in a listening room (with normal absorption and other than a tiny room), is completely ridiculous. The only time that would happen would be with a highly directional, two-dimensional loudspeaker with poor dispersion (this type of speaker would sound bright and “flat” so long as your listening position remained on axis with the tweeter). The moment you moved away from that alignment, the speaker would sound dull and lifeless due to the poor acoustic-power response into the listening environment. And perhaps you prefer the strong, flat on-axis response with limited dispersion in the midrange and treble. I’ve been there, and I can tell you it wears “thin” after a short period of time. I had a pair of B&W 801s Matrixes were beautifully flat and smooth on axis, but were lacking in spaciousness due to less-than-ideal off-axis smoothness in the upper midrange and in the highest treble. These speakers are ideal monitors speakers, but they had to be pointed right at you, and you could not be far back in the listening room. Furthermore, after living with that for several years I realized that “music” isn’t like that at all. But if you want to believe that it is, by all have at it.

If you close-miked your AR-3a woofer, and you got uneven response, you’ve either (1) got a problem with your woofer/cabinet damping/crossover or (2) your microphone needs calibration. The bass response of your AR-3a woofer should be 38-600 Hz (with the 3a crossover connected) ±1.5 dB. This is the actual 2π anechoic response of the woofer, and it should be closely approximated with close-miking.

All AR speakers of this era were 2π designs, not 1π. The only 1π design I know of is the Allison: Three corner speaker or possibly the Klipshorn corner horn. If you placed an AR-3a on the floor against the wall or in the corner, 1π-fashion, you would have excessive-bass output (at least 3 dB elevation not including room effects). To say that the bass in an AR-3a is “shy” is ludicrous. If you prefer accentuated, unnatural bass like many (and I might add many JBL) speakers, then a speaker with low distortion and flat output down to the lower limits of music probably isn’t for you.

--Tom Tyson

[tysontom]

I don't think so. The AR demos placed live musicians and more or less anechoically recorded reproductions of those musicians into the same (concert or other demo) space. This is not the same as recreating the sound of a concert space in a different space, such as a home living room. For all the attempts that audio designers have made over the years, whether with wide dispersion speakers or multi-speaker surround sound, this has yet to be achieved at any "state of the art."

Genek,

I suspect that you have misinterpreted what was happening in the live-vs.-recorded concerts with the AR-3. The Fine Arts Quartet had to be recorded out doors in a mostly anechoic space to avoid “double reverberation” during the playback. In this fashion, the playback from the AR-3s into the audience was exactly the same thing as the music being played by the musicians, and the actual playback was alternated back and forth at intervals between the live performance and the AR-3s. Virtually no one, except for those sitting on the front row hearing some slight tape hiss, could ever tell the actual switchovers. This would include the approximately 10-12,000 people who actually attended these concerts during a three-four year period. By using an anechoic recording, the AR-3s didn’t reproduce the reflections from the instruments and the reflections from the speakers themselves simultaneously during playback. This is one of the biggest obstacles of doing LVR, and the main reason that few people understand how its done.

Incidentally, after these concerts, which were done in the early 60s, AR sales began to rise steadily until a peak in 1966, with AR's market share at 32% of the entire domestic speaker market. Probably a lot of that success was due to the perception by music lovers that AR speakers -- especially the AR-3 -- were extremely accurate reproducers.

--Tom Tyson

[Shacky]

Shacky,

This characterization of Villchur and Kloss isn't truly accurate. Both of these speaker pioneers certainly did use subjective techniques to evaluate the results of their testing, listening sessions and so forth, and Kloss probably used that means as a primary testing methodology once he had done initial measurements at the start of KLH in 1957. Villchur used the AR-3 Live-vs.-Recorded concerts as a subjective validation of his objective-measurement techniques, and these concerts demonstrated conclusively that his AR designs -- which measured extremely well -- were also very accurate reproducers. Perhaps this was not to everyone's "taste," but these AR speakers were accurate reproducers, and that is the very definition of "high fidelity." Moreover, Villchur felt that loudspeakers were really not different from any other audio device with respect to objective-measurement techniques; i.e., you could measure a loudspeaker just as you could measure an amplifier, preamp or pickup cartridge in the turntables of the day. It was more difficult, for sure, but he rigorously measured every parameter of loudspeaker performance that could be measured during that period in history, and he published every detail of that information -- the first for any loudspeaker manufacturer. AR loudspeakers were primarily designed and refined using laboratory measurements, and then the final results were put to the subjective test establishing their accuracy -- probably the main reason for the continued popularity of AR speakers after fifty years.

--Tom Tyson

Tom,

I see what you mean. I need to stop saying it that way. But boy these AR's sure sound good to these ears

Jim

[tysontom]

Tom,

I see what you mean. I need to stop saying it that way. But boy these AR's sure sound good to these ears

Jim

Jim,

I think it was Gerald Landau, former Director of Marketing at AR for many years, who was quoted in Audio Times (an old industry weekly magazine), "the good thing about AR speakers is that once they are sold, they stay sold." He simply meant that there was a high degree of satisfaction with AR-speaker owners, probably because the speakers were accurate reproducers and not flashy, bright-sounding "hi-fi" speakers so prevalent in the day (and emerging again in what's left of today's market). This is interesting in that in the "audiophile" market, high-end speakers don't stay "sold" for long; dissatisfaction sets in quickly, and listener fatigue overwhelms the owner, usually forcing an equipment upgrade of some sort. "It's a never-ending struggle against the forces of evil."

--Tom Tyson

[genek]

Double post, ignore this one.

[genek]

I suspect that you have misinterpreted what was happening in the live-vs.-recorded concerts with the AR-3.

No, I was trying (perhaps not successfully) to point out that the live vs recorded was exactly as you described it, and was not an attempt to recreate one reverberant environment in a different one. This was in response to a comment that seemed to me to suggest that it was.

[Zilch]

Another problem Toole has is that he is measuring speakers in the direct field, and when you do that even small shifts in microphone position will cause response anomalies. Because of that, it is ridiculous to print out an on-axis direct-field full-system curve of any kind, because even a modest upward or downward shift in microphone position will present a different measurement. Ditto when trying to measure at horizontal off-axis angles. In Toole's book he regularly prints on-axis and horizontal off-axis curves as if they would be that way at all vertical locations within the listener's normal seating range. However, curves like that are misleading. You would have to do dozens of them to make them meaningful, and then, of course, they would be so complex that it would be hard to interpret them. Allison showed that in his 1970 AES preprint that I referenced.

We discussed that briefly at #28; it's simply not true with a well-designed speaker. Here, for example, is JBL 4412, a conventional three-way with a dome tweeter. See the horizontal and vertical off-axis response curves, which define the interaction between the drivers. Clearly, the behavior from 500 Hz to 20 kHz is "regular;" I suppose you'd characterize these as "narrow dispersion," since they are down 6 dB at 50° in both directions in the horizontal, for a nominal beamwidth of 100°. You've not yet specified your criterion for what might comprise a "wide dispersion" speaker:

http://www.jblpro.com/pub/obsolete/4412.pdf

For comparision, here is 4430, a 100° axisymmetric constant-directivity design, holding steady at - 6 dB across the same spectrum, interrupted only by the vertical nulls at the 1 kHz crossover frequency, which are well defined:

http://www.jblpro.com/pub/obsolete/443035.pdf

By contrast, below are the horizontal and vertical polars of AR3a as I measure them; the horizontals separately for inboard vs. outboard (they are not mirror-imaged,) and the verticals over a much narrower beamwidth, +/- 8.13°, a typical vertical listening height. These findings are remarkably similar to those shown by Allison under similar conditions in his 1970 paper.

It's certainly disingenuous, in my view, for you to condemn Toole's (and the industry at large's) measurement methodology for revealing AR3as for what they are, a veritable festival of phase interference chaos in the direct field....

[Pete B]

I find it hard to believe that this is being debated here, as the fundamental research was done so many years ago.

It was so long ago that I learned about the importance of a smooth on axis response, I'm not going to call it the

"direct field", that I don't remember exactly when it was. It was certainly before I got to college, probably explained

to me by my older brother. Then it was required reading when I studied loudspeaker design under Professor Wadesworth

at WPI. An old paper covering the subject from the November 1958 issue of the Proceedings of the Institute of Electrical

Engineers is:

"A Survey Of Performance Criteria and Design Considerations for High-Quality Monitoring Loudspeakers"

By D. E. L. Shorter

It is also reprinted in the green Anthology issue of the AES.

The paper has many excellent references going even further back.

I believe that the understanding of the importance of smooth on axis response was a key requirement

in the development of such legendary designs as the LS3/5a, many KEFs, B&Ws, Spendors, and others. And it is

one thing that made those British designs sound so good. I expect that Toole, Small and others who have been

critical of AR and Allison speakers are probably advocates of this requirement.

[genek]

It's certainly disingenuous, in my view, for you to condemn Toole's (and the industry at large's) measurement methodology for revealing AR3as for what they are, a veritable festival of phase interference chaos in the direct field....

I'd be perfectly willing to accept response curves that look like a cross between a roller coaster and a buzzsaw blade, so long as someone can actually explain how they produce the sound we're all used to hearing come out of these speakers. It seems to me that this discussion sounds more like a bunch of designers measuring raw drivers and prototypes and arguing about how an unfinished speaker design project is going to sound, rather than analyzing a speaker that has been a fait accompli for more than 30 years (or maybe 40+, since the live vs recorded demos of the original AR-3 seem to have become such a big part of the discussion) to determine why it sounds the way that it does.

[soundminded]

I'd be perfectly willing to accept response curves that look like a cross between a roller coaster and a buzzsaw blade, so long as someone can actually explain how they produce the sound we're all used to hearing come out of these speakers. It seems to me that this discussion sounds more like a bunch of designers measuring raw drivers and prototypes and arguing about how an unfinished speaker design project is going to sound, rather than analyzing a speaker that has been a fait accompli for more than 30 years (or maybe 40+, since the live vs recorded demos of the original AR-3 seem to have become such a big part of the discussion) to determine why it sounds the way that it does.

Just as a point of fact, without regard to which speaker or what their other merits are, there are no multiway loudspeaker systems which do not exhibit very substantial phase interference phenomena in the region of their crossover frequencies. This is an inevitable consequence of the fact that their sound waves are propagated from two diffent points in space and/or time, Correcting one alone will not eliminate or necessarily even reduce the phenomena. What the exact physical effect will be depends on the geometry of the relationship between the drivers and between each driver and the listener, the frequency (wavelength) in question, and the difference in propagation delay between the drivers. (Propagation delay is the time it takes between the application of an electrical signal to the voice coil and a corresponding movement of the cone.) If two drivers are at the same loudness in their region away from their crossover points, when they add in phase, they will add 3db to the output. When they add out of phase, they can cancel each other out completely. A butterworth filter crossover network where both drivers have the same nominal crossover frequency such that each will be down 3db at the crossover frequency will be flat where the fields of the two drivers add in phase. Whether or not the interference pattern where they are out of phase has audible consequences depends on many factors such as how tightly spaced the troughs are across the area of spectrum where they occur at. They may be inaudible. For two drivers to produce sound which is in phase at the listener's location, they must coaxial and their propagation must be in sync in time. Since propagation delays for tweeters are usually shorter than for woofers and would be mounted in front of a woofer, a time delay circuit for the signal fed to the tweeter through a separate amplifier would be required and the listener would have to be on axis. So called phase coherent or time corrected speakers was one of the most widely exploited advertising scams in speaker marketing in the 1970s. No such thing as a phase coherent multiway loudspeaker ever existed on the market.