179 replies to this topic

[genek]

On to another subject:

Zilch said, "and we'd be best served by figuring out the factual basis for what is likable about ARs."

I posed the very same question myself (after good-naturedly chiding Speaker Dave for not tackling the question himself), and I posted my impression.

I haven't heard from anyone else, but since Zilch has posed the same question, I'd love to hear his and others' responses, in very specific terms, as I tried to do in Post #49 in this thread.

I gave up asking that one a while ago, because everybody who might have the technical chops to address it seems more intent on defending their own pet theories about what is and isn't "ideal" in speaker design rather than approaching the speakers as existing phenomenon to be characterized. And even those who are trying to characterize seem unable to do so without editorial comments about the validity or lack thereof of the goals behind the design, as if that really matters for something that was built more than 40 years ago and now sits physically before us as a fait accompli. And let's not get into certain peoples' inability to discuss any of this without taking personal potshots at other posters.

Until someone makes a presentation of "why it sounds the way it does," rather than "why it doesn't sound the way it should, the way it was intended to or the way most people like a speaker to sound today" and then demonstrates the accuracy of their characterization by building another speaker that duplicates it in measurement and listening experience, we'll continue to be treated to dueling opinions that constantly hover on the edge of closing down threads.

[tysontom]

I'm quite sure this is absolutely correct--the real reason for using the 10 Pi's and not the LST was to confer credibility and acclaim onto their current TOTL speaker, the 10 Pi.

It's a shame that the Grover LvR's didn't get more publicity. IMO, this demo was several orders of magnitude more difficult than emulating a string quartet, and the achievement of the 10 Pi in emulating the power, impact, and frequency range of a live drum set far surpassed the AR-3's achievement in reproducing a string quartet. Yes, a string quartet has all kinds of subtle nuances and very high frequencies, and a cello can reach down fairly low in frequency--but the dynamic demands on the system don't begin to approach what Grover's drum set demanded. It was also a very difficult demo for Grover, the performer, much more so than for the members of the FAQ.

There was also the time period to consider--in 1962, "stereo" was relatively new, solid-state was just coming on the scene, and the AR-3's were pretty unique as speakers. By 1976, stereo was old hat, high-power amps/receivers were commonplace, and the audience/market for 'gear' was mostly younger people, not middle-aged suburbanite homeowners like in 1962. Culturally/socially, the impact in 1976 couldn't match that of the L v R demos of the '60's.

Steve F.

I agree with Steve about the intensity and impact of the Neil Grover demonstration, and the fact that it was more difficult on that basis than the AR-3 LvR concerts (which actually began in late 1959 and ran into the early 1960s). However, in terms of faithfully recreating the live sound, the softer ensemble tone nuances of string instruments was arguably more difficult to match -- and changes would have been immediately noticeable -- than the higher-intensity, more frenetic Neil Grover drum demonstration. This is conjecture on my part. Whatever the case, Acoustic Research squandered a public-relations opportunity with the Neil Grover demonstration. By contrast, Villchur parlayed the Fine Arts Quartet concerts into a great AR public-relations windfall, with advertisements and fanfare that went on for years (even today we are talking about it).

There is no doubt whatsoever that the Neil Grover demonstration was far more difficult with regard to power required. The AR-10s consistently required 800+ watt peaks (vs. 120-watt peaks on the AR-3 LvR) to reproduce the drum sound -- mainly rim shots and cymbals according to Victor Campos; in fact, Campos had difficulty in finding an amplifier that could reliably perform on this basis for the AR-10s. Even the highly regarded Dunlap-Clark Dreadnaught 1000 could not sustain the high power into low impedances for very long, and eventually other amps were used. The subtle ensemble reproduction and plucked strings from violins and guitars were reproduced clearly and faithfully by the AR-3, and even the drum and percussion sound of the 1910 Seaburg Nickelodeon were reproduced without a hitch by the AR-3, but there was never the impact and power that came with the Neil Grover live-drum sound.

--Tom Tyson

Fig. 1 Neil Grover/AR-10Pi Internal Construction
Fig. 2 Neil Grover/AR-10Pi Wiring

Attached Thumbnails

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[genek]

Very simply: Why do you think the Classic ARs were and are so popular?

Actually, what I was hoping for was a technical characterization of their sound leading to someone building a new speaker whose is indistinguishable from that of the original, similar to the many attempts that are being made to chemically analyze and duplicate pricey French wines such as Chateau Margaux. Attempting to explain popularity is just going to get us more dueling unprovable theories.

[Steve F]

Actually, what I was hoping for was a technical characterization of their sound leading to someone building a new speaker whose is indistinguishable from that of the original, similar to the many attempts that are being made to chemically analyze and duplicate pricey French wines such as Chateau Margaux.

Attempting to explain popularity is just going to get us more dueling unprovable theories.

No, it's not. I gave very specific, plausible reasons in my post, and I'm sure the rest of the Forum could come up with many more. It'd be interesting reading.

Your desire for "a technical characterization of their sound leading to someone building a new speaker whose (sound) is indistinguishable from that of the original" is also very interesting, but it is a completely different topic than the one I asked.

Perhaps you should split the thread. I want to know from this august group of widely varying ages, viewpoints, and experiences to what do they attribute the Classic ARs' enduring popularity?

Simple question. Distinct topic from yours.

Steve F.

[genek]

No, it's not. I gave very specific, plausible reasons in my post, and I'm sure the rest of the Forum could come up with many more. It'd be interesting reading.

Your desire for "a technical characterization of their sound leading to someone building a new speaker whose (sound) is indistinguishable from that of the original" is also very interesting, but it is a completely different topic than the one I asked.

Perhaps you should split the thread. I want to know from this august group of widely varying ages, viewpoints, and experiences to what do they attribute the Classic ARs' enduring popularity?

Simple question. Distinct topic from yours.

It really isn't, because you can't arrive at a consensus on a "factual basis" for the speakers' popularity while everybody's still arguing about what they really do. But there's no reason to split the thread between the questions, because as I have already said, I've concluded that my question will never be answered anyway. Maybe you'll have better luck with yours, but I think it more likely that in any discussion that is not narrowly focused on the tech, certain posters will inevitably start taking their usual personal potshots at each other and I'll end up closing the thread. Again.

[genek]

I've split Steve's request for peoples' opinions on AR popularity off to a new thread so it won't get lost in "beam or not beam." Let's see how long it lasts there.

[Steve F]

I have one of the original tapes that was made by AR of Fine Arts Quartet, and in this particular tape (this was an early tape recording of the musicians, AR-3s and the audience's reaction during an actual concert), Leonard Sorkin, First Violin, stopped the music about half-way into the concert. He said, "…by the way, could we have a show of hands on how many people could detect the switchovers from our live playing to the reproduced music through the speakers?" There was a rather large showing of hands. He said, "…well, I'm sorry to tell you this, but except for the first two bars, the entire part was playing through the AR-3s."

Image One: AR Live-vs.-Recorded concert

The caption in this AR pic is another example of the amazing class and dignity that this company had during the 50's-early 70's time frame. They actually call out Briggs and Wharfedale and cite their L v R demos as well.

In the 1970-72 brochure, on the 3a page, they quote Consumer Guide saying, "In our opinion, one of the two finest speakers available today." AR puts an asterisk next to the quote, and at the bottom of the page, they say, 'The other is the KLH-12.' !! They give their no. 1 rival a nod of respect--in their own brochure!

What company has ever done this, in any industry? Can you imagine a BMW ad, citing their 3-Series Car and Driver magazine "10 Best" selection for the Xth year in a row, and BMW saying in their ad, "And the Honda Accord was selected best family sedan for the Xth year in a row also."

Not a chance.

But AR was so classy, so 'above the fray,' that they routinely did this kind of thing and it conferred amazing, understated credibility on the company.

The Classic-era AR was a once-in-a-lifetime company, from every angle.

Steve F.

[Zilch]

I haven't heard from anyone else, but since Zilch has posed the same question, I'd love to hear his and others' responses, in very specific terms, as I tried to do in Post #49 in this thread.

And I have provided my answer a dozen times, including here, at least to the extent that I understand it, and that is constant directivity, and ultimately, even Howard agreed to the terminology. That's also what the Linkwitz postings were about.

Soundminded just said the same thing, though he apparently has zero clue that it is easily accomplished today, having earlier opined that the example I previously posted, a pioneering Speaker Dave design from 1980, in fact, could not possibly work....

[Zilch]

I'll say it again, also for the dozenth or more time, that wide and very wide-angle dispersion adversely affects both spatial and sonic quality, which Howard also concedes. "Concert hall realism" doesn't give a whit about either, but there is a very real sense in which Howard is a victim of his preferences -- wide dispersion requires a "perfect" listening space; it puts the room in control of the result. Even then, only multi-channel can make that work optimally, as Howard further concedes.

The more contemporary answer is to minimize the influence of the room rather than rely upon it, and that is easily accomplished, two-channel even, via more moderate dispersion constant-directivity sources, which sacrifice neither localization nor spaciousness when suitably deployed in ANY room.

AR's LvR successes are not evidence of the superiority of anything. What IS compelling is that science, the industry, and the marketplace itself have each and all long since repudiated and abandoned the very principles those successes are herein alleged to have established as transcendent.

If there is merit in these early designs, that may best be found by looking elsewhere than to these outmoded theories....

[speaker dave]

Result: no change in spectral balance at all with either procedure. I also tried it at arm's length (about two feet), and then I could hear a slight difference, and I mean slight. Frankly, I was surprised, because I actually thought the differences would be seriously audible. The differences between so-called identical speakers when compared this way were audible, and yet this test of yours was not even close to that kind of contrast.

So, good try, but I was not impressed. Yeah, I sure did learn something: I was correct the first time.

Howard Ferstler

Well I tried the ruler test again with my long suffering wife doing the honors. My home theater is a largish bedroom. The system was a Snell XA75 with a 1" dome with slight "added directivity" from a wide flare. I could certainly hear the effect of the ruler very readily when I did it myself at arms length. I normally sit about 12 feet away. From that position it was still easily audible as a single pitch moving up and down in frequency as the ruler got closer and farther from the dome. It wasn't "dramatic" and I'm not sure that it would be a strongly noticeable effect if it weren't for the constant motion. Still, it is an aberation that degrades the response of the dome and one that you would want to correct if at all possible. (Well, I would.)

I was surprised that I could hear it from the back corner of the room at about 19ft away. Both the listening position and that corner were to the right of the speaker while the ruler was on the left side. This would be the side that reflected energy would favor. It was also nearly as audible on the back left corner, which could not be a reflection but would have to be a diffraction effect.

If you want to hear other reflection effects an interesting one is to hold a piece of paper over a hard surface such as a stone or marble counter top. Ripple your fingers over the back of the paper to create a constant crinkling noise. While doing that move the paper up and down from the counter surface. You will hear distinct pitch effects that will swing up and down in frequency. The direct sound and the reflection off of the hard surface have a time difference that is constantly changing due to the up and down motion. This creates a variable pitch comb filter.

You can also hear pitch changes from floor bounces if you do deep knee bends at a distance form your speakers. Carpet is surprisingly reflective.

Fun with science.

David

[speaker dave]

The concerts were about as scientific as one can imagine in this business. Rather than subjectively evaluate speakers with commercial recordings (which themselves introduce uncontrolled variables) or measure them and then speculate about what does and does not matter with those measurements, Villchur actually recorfed an ensemble anechoically and then did A/B comparisons between the performers themselves and speakers playing back the recordings. Just what kind of listening tests could you come up with that would be any more exacting? And don't mention Toole's "popularity contests."

Howard Ferstler

But not exactly a comparitive test, being a test group of one. Plus didn't they have to equalize the system for a best results? Did they offer the audience a comparison between multiple systems and have them choose the the most accurate?

As to the "popularity tests", you degrade you own argument when you denigrate what are the most rigourously controlled tests I know of. Rather than "popularity" the listeners are marking the systems for factors of clarity, fullness, spaciousness (a big one, I'm told), etc. Factors are added up to come to an overall "Fidelity rating". The methodology and statistical analysis of results have been well published and survived much scrutiny.

I'm still picturing that opera singer next to the Edison. Must of been a hell of a gramophone.

[Zilch]

Another easy one is with a free-standing horn/waveguide: have someone move it back and forth atop the bass bin to hear the crossover region phase transitions.

[It sounds like a flanger.... ]

[soundminded]

Yes, it is fun. I am fairly sure that much of that pitch changing with knee bends also involves the lobing we have with the speaker drivers interacting. It is not so audible with some speakers, but with my MTTM Allison and home-built units the vertical radiation is focussed, and so the effect is there.

Howard Ferstler

Changes in pitch resuling from the motion of a sound reflecting object towards or away from the source of sound or towards or away from the listener (or of the relative position of the source and listener with respect to each other) is usually attributable to the doppler effect, not diffraction.

[soundminded]

Interesting. I remember one evening as I was sitting in a rocker in my living room. The refrigerator (not exactly a loudspeaker) was running and as I rocked back and forth the pitch of the motor noise (low in level, because as with most of the things I own it is a very good refrigerator) shifted audibly.

Howard Ferstler

The major effect of interest the beveled edge molding of an AR3/AR3a cabinet would have is reflection, not diffraction. The link below illustrates the phenomenon of diffraction.

http://www.google.co.../...&tbs=isch:1

As can be seen from the diagram, diffraction of sound which is analagous to diffraction of light occurs when sound hits a sharp edge or passes through a narrow slit. Alternating bands of dark and light regions in the case of light and loud and soft areas in the case of sound occur in the area that would ordinarily be in shadow. In the case of the loudspeaker this would be to the extreme side, or directly above and below the cabinet. This is due to the bending of the sound around the sharp edge.

The amount of sound contributed by the reflections off this molding compared to the direct sound arriving from the tweeter is probably insignificant. Comparing two such speakers, one with the wood left bare and one with it covered by sound absorbing material would indicate the difference. If anyone tries it I would be interested to hear the results. The difference can be measured and the number of decibels added can be determined.

The doppler shift occurs because as you move towards a sound source, the number of wave crests you encounter in a given time increases. When you move away from it, it decreases. A typical example of this is the first increasing and then decreasing pitch of a train whistle as a train passes you by. Same for a car horn that has a constant pitch when it is stationary.

[Zilch]

There are two approaches involved. First, those who favor the direct-field, narrow-dispersion approach want to hear just the recording, or as much of it as possible, without the playback room interfering. They want to hear through the speakes to the microphones. Fine. They want outboard headphones sitting out there. OK, go for it.

That's not what we advocate.

You've never gotten it, and you're too deeply "embedded" for it ever to be likely that you will....

[Zilch]

Yes, the Villchur concerts took place in rooms that were larger than typical playback areas in typical homes. However, no matter how large the room any so-called diffraction effects and anomalies generated by assymetrical placement of drivers on the baffles should have been apparent. Indeed, in a larger space, where room-generated reflections would be subdued and the listeners more bathed in the direct field than in normal home-listening rooms, diffraction and driver/baffle effects should have been MORE audible, not less.

Would this not also be true in a heavily damped listening space?

[speaker dave]

Another easy one is with a free-standing horn/waveguide: have someone move it back and forth atop the bass bin to hear the crossover region phase transitions.

[It sounds like a flanger.... ]

It doesn't change the power response into the room so you can't possibly hear it. Deluding yourself again!

David

[speaker dave]

Yes, it is fun. I am fairly sure that much of that pitch changing with knee bends also involves the lobing we have with the speaker drivers interacting. It is not so audible with some speakers, but with my MTTM Allison and home-built units the vertical radiation is focussed, and so the effect is there.

Howard Ferstler

Yes, It could involve lobing if that is present, but there is a floor bounce component also. You can take a vertical array and put it on a stand sideways (removing the "vertical" lobing) and still hear the same effect.

But it ain't Doppler.

David

[speaker dave]

The major effect of interest the beveled edge molding of an AR3/AR3a cabinet would have is reflection, not diffraction. The link below illustrates the phenomenon of diffraction.

[

We tend to be a little sloppy with our terminology. Per you link, diffraction is the bending of waves around a blocking object to filll the "shadow" behind. Due to the change in impedance it always causes a reflection. Interestingly, these reflections are out of phase with the wave, unlike reflections from barriers which are in phase.

I was looking at Olson's study on enclosure diffraction/reflection and he showed a worst case peak to trough of 10dB (I'm guessing that would be audible) for drivers mounted dead center in a square or circle. Typically 2 to 3 dB effect for other cabinets.

David

[soundminded]

We tend to be a little sloppy with our terminology. Per you link, diffraction is the bending of waves around a blocking object to filll the "shadow" behind. Due to the change in impedance it always causes a reflection. Interestingly, these reflections are out of phase with the wave, unlike reflections from barriers which are in phase.

I was looking at Olson's study on enclosure diffraction/reflection and he showed a worst case peak to trough of 10dB (I'm guessing that would be audible) for drivers mounted dead center in a square or circle. Typically 2 to 3 dB effect for other cabinets.

David

Nearly 90 degrees off the speaker's axis in an AR3/AR3a, there is a reflector around the perimeter which in aggregate is approximately 1 square foot in area (4 foot perimeter and no more than about 3" wide) and is evenly distributed. It reflects at what appears to be about a 30 degree angle. Are you saying this reflector adds 10 db to the speaker's output at any frequency compared to the drivers without this reflector? I find that hard to believe. Certainly the tweeter's output 90 degrees off axis is relatively small compared to its forward output. To the degree that these reflections exist, they will create multiple comb filtering, so many because each point along the reflector is another source that the interval of frequency nodes and number of nodes at any given point in space are so numerous that will tend to cancel each other out. At least that is the theory. That is why I asked for any reference to measured data. It strikes me that like many audiophile notions, this type of generalization is not only theoretically flawed, it is not proven out by experience. This is typical for the arguments for wires, vacuum tubes, vinyl phonograph records, and many other audiophile notions that run contrary to factual knowledge. In fact audiophile notions generally fly directly in the face of real scientific knowledge and the experience of engineers even if the audiophiles have gone into the manufacturing business and have products to sell.

Reflections off the floor are critical to the sound of many musical instruments. For example, many wind instruments like clarinets and oboes direct their sound almost exclusively at the floor. The way in which the performing stage is constructed can directly affect the bass response of an auditorium as it is a critical reflector of large area near the sources of sound. Cancellations due to the Allison effect can easily be equalized out.

Diffraction around the back and sides of cabinets is of far greater concern at low frequencies than at high frequencies. This is only one reason why a forward firing speaker will sound muffled from behind. Only the lower frequencies radiate omnidirectionally to the sides, top, bottom and back of the cabinet and create reflections within the room that drastically alter the tonal balance of the speaker. This is why there is little correlation between the on axis anechoic FR and the real room FR when all of the sound reaching the listener including the reflections are collected. Moving the speakers away from the walls and adding sound absorbing material only marginally mitigates the problem.

"We tend to be a little sloppy with our terminology."

I've noticed. It hardly stops there though.