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Reverberant vs Direct field strengths


Howard Ferstler

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Could have fooled me. Seeing the picture of the speakers sitting there on the concert hall stage sure implies they produce concert hall sounds.

If not, why put them there in the first place?

Because that was how they were used in the hall for the performance. Varese's composition mixed live instruments and recorded sound; IOW, the the audio equipment was used as a musical instrument.

The 3a's did produce concert hall sound for that occaision because they were used in a concert hall, but they did not reproduce concert hall sound.

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The application described was the use of AR-3a's for a performance in the hall, not a reproduction of the hall. The material being played on the speaker was an actual part of the performance, and the statement you quote is intended to express that the use of AR-3a's reproduced the electronic portion of the program (which were modified recordings of various acoustic sounds) in an undistorted fashion and did not create a "PA system in an acoustical hall" sound. Concert source realism rather than concert hall realism.

http://www.classicalarchives.com/work/154019.html

Yes, this 3a ad is somewhat open to interpretation. I tend to think that AR is saying that 3a's in Symphony Hall are accurate and uncolored enough to have been included in the original performance itself, rather than AR implying that the 3a would re-create the concert hall effect in your living room. I could be wrong.

Still, their lit never comes out and says anything about their wide-dispersion drivers having been developed for the purpose of re-creating the Hall; on the other hand, they do say quite explicitly that the wide-dispersion approach was done for reasons of both listener and speaker placement flexibility.

All of this is quite separate from whether you do or don't believe the 3a achieves its goal of wide dispersion, and it is distinctly different from any of our discussions here about the importance or relevance of the far field in home listening environments. In their literature, AR simply presents that listeners 'appreciably off-axis' can hear the 3a as clearly as listeners directly in front of the speaker. They never mention the 'far field,' and they don't say that it is or is not important.

Our Kitchen discussions are wide-ranging and energetic. But we should probably exercise some caution when ascribing to AR product design/philosophy motives that may not, in fact, be true.

Steve F.

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But AR—as stated very clearly in their own literature—presented their wide-dispersion dome drivers as chiefly having the benefit of better listening area coverage and more flexibility in listener seating. Nothing more. They never said in their lit or advertising that the 3a’s dispersion would absolutely recreate a concert hall-like experience.

It's kinda fundamental, actually: spraying the room from two omnidirectional sources and then ignoring the requirements of generating a phantom image, namely, listening from midway between them, defeats a core purpose of stereophony. The soundstage may be "huge," as many frequently observe, but the localization cues are all but gone; it's diffuse sonic mush we're hearing, and there is no real envelopment, either, only make-believe, as LEV cannot be created from two sources in a small room.

There are ways to generate a broad stereophonic image rendition zone from two sources employing defined directivity without sacrificing the experience itself which provide a "locked" image independent of listener position. They are somewhat disconcerting when first heard, we are so used to stereo behaving badly in this respect. Ultimately, a center channel solves a large proportion of these problems, but L/R directivity issues remain for those listening from outside the true "sweet spot." In many respects, soundstage and imaging are mutually exclusive when conventional methods are used to produce them, but once understood, there are available alternative means to accomplish and enjoy both with their respective contributions to realism concurrently.

Program content plays a significant role in this as well: how much significant differential L vs. R stereo content is present in a symphonic recording when compared to that of a jazz combo? Consider this also -- how far off-axis do we actually sit in the concert hall? What is the "real" source width?

Could have fooled me. Seeing the picture of the speakers sitting there on the concert hall stage sure implies they produce concert hall sounds.

If not, why put them there in the first place?

Here, then, is the obligatory distasteful remark: They DID fool you; that was the intent, and they were quite good at disingenuous sleight of hand. You didn't think through their message, and neither would 99% of those seeing that ad.... :rolleyes:

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It's kinda fundamental, actually: spraying the room from two omnidirectional sources and then ignoring the requirements of generating a phantom image, namely, listening from midway between them, defeats a core purpose of stereophony. The soundstage may be "huge," as many frequently observe, but the localization cues are all but gone; it's diffuse sonic mush we're hearing, and there is no real envelopment, either, only make-believe, as LEV cannot be created from two sources in a small room.

My 2ax's and 3a's both produce a "huge" soundstage, with the sound source seeming to be "locked" from listening locations as far as 2 or 3 feet outside the zone between the speakers on either side, and depending on the source material may or may not produce what I perceive as "locaization."

I wouldn't argue with a description of symphony recordings as "diffuse," but having never sat any closer to an orchestra than row 20 or so, that's not terribly inconsistent with my inpression of the real thing. Possibly a room-wide "diffuse sonic mush" is doing a fairly credible job of reproducing the sound of what comes from the front of a concert hall's "reverberant field," but what's coming from the sides and back are pure living room; I've never gotten the impression that I might have stepped through some sort of space warp into Carnegie Hall.

With recordings of small groups, such as in a jazz quartet, even outside the "sweet spot" I can discern separate virtual locations for a piano, singer, bass, etc. Whether these accurately reflect the original locations the performers actually occupied in the studio, I couldn't tell you, but since most of my recordings don't include photos of the performers being recorded any difference is rendered meaningless to my listening experience. Since my living room is not much smaller than many of the settings in which I have heard these kinds of performers play, for this material I actually can close my eyes and experience a relatively convincing recreation of a live venue.

My smaller 6's produce pretty much the same effect as the bigger speakers, except that unlike the 2ax's and 3a's I cannot stray from the zone between the speakers without the sound source seeming to move to the left or right.

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It's kinda fundamental, actually: spraying the room from two omnidirectional sources and then ignoring the requirements of generating a phantom image, namely, listening from midway between them, defeats a core purpose of stereophony. The soundstage may be "huge," as many frequently observe, but the localization cues are all but gone; it's diffuse sonic mush we're hearing, and there is no real envelopment, either, only make-believe, as LEV cannot be created from two sources in a small room.

There are ways to generate a broad stereophonic image rendition zone from two sources employing defined directivity without sacrificing the experience itself which provide a "locked" image independent of listener position. They are somewhat disconcerting when first heard, we are so used to stereo behaving badly in this respect. Ultimately, a center channel solves a large proportion of these problems, but L/R directivity issues remain for those listening from outside the true "sweet spot." In many respects, soundstage and imaging are mutually exclusive when conventional means are used to produce them, but once understood, there are means to accomplish both concurrently.

Program content plays a significant role in this as well: how much significant differential L vs. R stereo content is present in a symphonic recording when compared to that of a jazz combo? Consider this also -- how far off-axis do we actually sit in the concert hall? What is the "real" source width?

Here, then, is the obligatory distasteful remark: They DID fool you; that was the intent, and they were quite good at sleight of hand.... :rolleyes:

The source width of a full symphony orchestra in a concert hall depends on how far away from it you sit. In the front row, It's over 90 degrees, less than 180 degrees. The 40 first and second violins alone comprise about half of that. In the back of the hall, the angle is usually less than 90 degrees. Maybe around 60 degrees. The vertical angle is very low. The most extreme relative front to rear location of the players is rather insignificant. Percentage wise they are close enough to each other not to matter although louder instruments like more powerful brass instruments are usually in the back. Large blocks of instruments like violins form a kind of continuum of source but they are not a point source, the sound of each one is not identical to another. This is important because they produce an effect as a group which cannot be duplicated by a single point source such as one direct firing loudspeaker system would produce. One assumes that the speakers were spread across the stage to simulate the orchestra rather than bunched together. I didn't see the photograph. Producing a convincing illusion of this with two direct firing point source loudspeakers is highly dubious.

A grand piano is an obviously large source of sound. Even in a large concert hall, it is no point source unless you get pretty far from it. In a home, depending on its size it can be a monster. My 5'-6" M (for medium) sized grand is just right for my 14 x 30 x 9 room that's about 4000 cubic feet. Neither Dr. Bose, the reviewers at Consumers Reports, nor the judge could have ever seen a full sized concert grand or the question of Bose 901 making one sound like it was 8 feet wide would never have been an issue. Steinway D, the most preferred of all of them is 8'-9" and the Baldwin SD-10 is 9'-6" and they sound every bit of it, they are quasi omnidirectional radiators filling the entire end of a room with sound. Some are even larger. Two point sources aimed at a listener no matter what their timbral balance or front radiating pattern whether AR3a or Geddes can't be made to produce that sound convincingly to anyone with normal hearing in both ears. How do I know? I've been trying for nearly 20 years with AR9. Substantial modifications of the original intended sound are necessary to get even close.

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One assumes that the speakers were spread across the stage to simulate the orchestra rather than bunched together. I didn't see the photograph.

It's six speakers, two groups of three about five feet apart in the center front of the stage. The speakers were not reproducing the orichestra, they were accompanying it. The intent was not to reproduce the sound of original musical sources, but to experiment with using electronics as an original musical source, to be treated in concert the same as a traditional instrument.

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The published FR curves for the GedLee Speaker are IMO horrible. It seems to me that this is no constant directivity speaker by any stretch of the imagination.

Despite my having linked you to the original Keele paper, you still do not understand constant directivity. For each design, a desired beamwidth is defined at -6 dB, industry-wide. I believe he considers this 10" waveguide to be a 70° design, i.e., +/- 35°. If you look at the curves for his 12" version, I believe you'll find it is better behaved. Frankly, in many respects, the cheapo E'Waveguide outperforms them both, and in the end, after measuring them, he concluded that they were "not as bad" as he expected, a major concession considering his vested interest.

He claims the notch in the on-axis response is an artifact of a "perfect" axisymmetric waveguide, interference from the concentric edge of the mouth. Calc the wavelength, and I believe you find this credible. No matter, he doesn't advocate listening on-axis, clearly an example of the "function following faulty form" approach you suggest, by redefining the axis with toe-in. He admits that an elliptical implementation of his design principles would mitigate the issue, but can't make them in his garage without investing in a professionally made mold. That design is shown in his early papers on waveguides, but no matter once again, as this would not alter his recommendation as to how they might be optimally deployed.

When Howard reads that "Geddes in a Nutshell" presentation, I suspect he will find that Roy and Earl agree on more points than he might ever have imagined.... :rolleyes:

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It's kinda fundamental, actually: spraying the room from two omnidirectional sources and then ignoring the requirements of generating a phantom image, namely, listening from midway between them, defeats a core purpose of stereophony. The soundstage may be "huge," as many frequently observe, but the localization cues are all but gone; it's diffuse sonic mush we're hearing, and there is no real envelopment, either, only make-believe, as LEV cannot be created from two sources in a small room.

There are ways to generate a broad stereophonic image rendition zone from two sources employing defined directivity without sacrificing the experience itself which provide a "locked" image independent of listener position. They are somewhat disconcerting when first heard, we are so used to stereo behaving badly in this respect. Ultimately, a center channel solves a large proportion of these problems, but L/R directivity issues remain for those listening from outside the true "sweet spot." In many respects, soundstage and imaging are mutually exclusive when conventional methods are used to produce them, but once understood, there are available alternative means to accomplish and enjoy both with their respective contributions to realism concurrently.

Program content plays a significant role in this as well: how much significant differential L vs. R stereo content is present in a symphonic recording when compared to that of a jazz combo? Consider this also -- how far off-axis do we actually sit in the concert hall? What is the "real" source width?

Here, then, is the obligatory distasteful remark: They DID fool you; that was the intent, and they were quite good at disingenuous sleight of hand. You didn't think through their message, and neither would 99% of those seeing that ad.... :rolleyes:

This is a very plausible explanation/solution to something that AR never explicitly said they were trying to solve. AR never mentions a rock solid “locked” stereo image or anything of the sort—they simply wanted people to be able to hear their speakers well off axis and not be restricted to sitting right in front of them. Whether we agree that their goal is worthy or not is not the issue. Whether we agree that their chosen means of achieving that goal is worthy or not is not the object of this discussion.

Likewise their use of the 3a image on the BSO stage. That’s called “marketing,” and using images or spokespeople that imply credibility for the product or service in question is an accepted business device. It’s up to the target customer to decide for themselves whether the comparison/implication carries any weight. I wouldn’t use the term “sleight-of-hand” to describe AR’s 1960’s-era advertising, as that implies a dishonest or sinister/deceptive intent, but that’s just my take. If Nike says that their sneakers are the choice of LeBron James (assuming they are), it’s up to me to decide whether that means that Nike shoes are really good or not. But Nike doesn’t suffer in my eyes for having said so. Other people are more sensitive to such third-party advertising, and they may, in fact, assign underhanded motives to such actions.

To each his own.

Steve F.

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Yes, this 3a ad is somewhat open to interpretation. I tend to think that AR is saying that 3a's in Symphony Hall are accurate and uncolored enough to have been included in the original performance itself, rather than AR implying that the 3a would re-create the concert hall effect in your living room.

I don't see anything ambiguous about the advertisement at all. Whoever was setting up that Boston Symphony performance chose AR-3a's to deliver the recorded portions of the piece. That's exactly the same as saying that Miles Davis or Herbert von Karajan chose ARs for their speaker needs. And yes, the reader decides how much weight any of those carry vs. some other speaker manufacturer saying that their product was the preferred choice of Led Zeppelin or Kurt Cobain.

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I don't see anything ambiguous about the advertisement at all.

It's no less disingenuous than the live versus recorded demos. Just as Carl suggests: implicitly, we're supposed to generalize that we should buy the speakers to enjoy their realism, in this case, the Boston Symphony experience, in our own living rooms.... :rolleyes:

I reviewed these surround speakers, along with the company's accompanying left, center, right, and subwoofer systems (making up their Epic Grand Master 5.1 speaker system) in issue 100 (July/Aug, 2004) of The Sensible Sound. In the review I commented upon their resemblence to the considerably larger Allison Model Four. Of course, the Axiom also has a bottom mounted mid/woofer driver. It measured very smooth in my listening room; indeed it was smoother than the main-channel speakers.

No doubt you took particular note of Toole's extensive discussion of the unique applicability of wide-dispersion loudspeakers for use as surrounds....

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Just as Carl suggests: implicitly, we're supposed to generalize that we should buy the speakers to enjoy their realism, in this case, the Boston Symphony experience, in our own living rooms.... :rolleyes:

And in this case you actually would be, at least for the recorded portion of Varese's "Deserts." It'd be just like having a few of the BSO players show up at your home to perform their part of the piece in your living room. :(

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If you look at the curves for his 12" version, I believe you'll find it is better behaved.

Here are his polars for the ESP 12, same as Summa, as best I can tell, which he measured at the same time (and thus, under the same conditions) as the E'Waveguide, which I previously posted here:

http://www.classicspeakerpages.net/IP.Boar...ost&id=4574

post-102716-1242716133.jpg

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It's no less disingenuous than the live versus recorded demos. Just as Carl suggests: implicitly, we're supposed to generalize that we should buy the speakers to enjoy their realism, in this case, the Boston Symphony experience, in our own living rooms.... :rolleyes:

The ad is not "disingenuous" at all--quite the contrary, it's as up-front and straightforward as can be:

"LeBron wears our sneakers, so they are obviously good and you should consider buying them."

Again, third-party ads are a common marketing strategy in all consumer industries, but their use does rub some people the wrong way. Apparently, you don't care for them. That's fine.

But it's not "disingenuous" according to the actual definition of the word. AR's motives in the ad are not deceptive or hidden in any way.

Steve F.

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Again, third-party ads are a common marketing strategy in all consumer industries, but their use does rub some people the wrong way.

There is also the fact that people and organizations that endorse products are often either paid or receive a huge discount or free product (ever wonder why "more hospitals use Bayer aspirin"...?). The text of the ad is not ambiguous in its meaning, except to those who are reading in their own preconceptions, but I would never say that any endorsement-based ad is not disingenuous without knowing the full circumstances under which the endorser came to be using the product.

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There is also the fact that people and organizations that endorse products are often either paid or receive a huge discount or free product (ever wonder why "more hospitals use Bayer aspirin"...?). The text of the ad is not ambiguous in its meaning, except to those who are reading in their own preconceptions, but I would never say that any endorsement-based ad is not disingenuous without knowing the full circumstances under which the endorser came to be using the product.

As Tom Tyson has reported in these pages on countless occasions, AR NEVER paid for their endorsements. AR was very above board in its advertising in that era. Very classy and understated. It's what a professor of mine once referred to as "2 + 2" advertising, where you let the reader draw the conclusion "4."

Steve F.

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As Tom Tyson has reported in these pages on countless occasions, AR NEVER paid for their endorsements.

That's easy enough to work around. You wine and dine and give someone product for free and if they keep it, ask them for their endorsement. Then you can 100% honestly say they use it and like it, but that's still not the same as them going out shopping, comparing your product to others and choosing yours because they prefer it over the others. As has also been reported, AR was never so nose-in-the-air that they were above doing basic salesmanship.

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That's easy enough to work around. You wine and dine and give someone product for free and if they keep it, ask them for their endorsement. Then you can 100% honestly say they use it and like it, but that's still not the same as them going out shopping, comparing your product to others and choosing yours because they prefer it over the others. As has also been reported, AR was never so nose-in-the-air that they were above doing basic salesmanship.

Draw whatever conclusions suit your purposes.

In the end, nothing is 100% and it's ultimately the responsibility of the reader to decide for themselves. If someone wants to believe that AR was either fundamentally dishonest and deceptive at one extreme or pure as the driven snow on the other, that's their choice.

Business is business, and some entities conduct their business more honorably than others. But it is a continuum, no question--even from event to event, much less company to company.

Steve F.

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Draw whatever conclusions suit your purposes.

What "suits my purposes" is to read as little into anything as possible. AR's ad in this case states that BSO chose to use the 3a's in a performance and gives their reasons for the choice, does so quite clearly and unambiguously and does not tell the reader what conclusions to draw from it. There is nothing in it that should either raise or relieve anyone's suspicions about how honestly or dishonestly the company did its business; that needs to come from other sources.

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The ad is not "disingenuous" at all--quite the contrary, it's as up-front and straightforward as can be.

adj.

not straightforward; not candid or frank; insincere

I am wrong. They were certainly sincere.... :rolleyes:

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Here are his polars for the ESP 12, same as Summa, as best I can tell, which he measured at the same time (and thus, under the same conditions) as the E'Waveguide, which I previously posted here:

http://www.classicspeakerpages.net/IP.Boar...ost&id=4574

This one actually looks much better than the other one. It's parallel curves indicate it comes much closer to its performance design goals within that context than the other speaker. But there are several hitches. As you move off axis, the midrange and treble get progressively lower in level compared to the bass output. It still has that peculiar dip of about 6 khz on axis. And of course positioning them and sitting in just the right spot to get the most out of them is critical. Compared to live music of course the sound fields it produces would be nothing similar, moving just slightly from one location to another should change its sound radically. It still seems to produce little low bass. I get the sense that it would sound worse to me than it measures, at least for the kind of music I prefer to listen to. But for your bon Jovi or whatever it is you like, I'm sure it will do just fine. Because in the final analysis, when there is no live reference to compare it to, who's to say what is right or wrong. That's the beauty of the industry today, everything is equal to everything else in our non judgemental world of political correctness, even when it comes to noise.

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This one actually looks much better than the other one. It's parallel curves indicate it comes much closer to its performance design goals within that context than the other speaker. But there are several hitches. As you move off axis, the midrange and treble get progressively lower in level compared to the bass output.

Within a +/- 30° listening widow, the levels are constant.

It still has that peculiar dip of about 6 khz on axis.

I explained that to you above. I'd be good if you actually read my posts, which you have previously stated you don't.

And of course positioning them and sitting in just the right spot to get the most out of them is critical.

Nope, wrong. The first reflections come from way off-axis

Compared to live music of course the sound fields it produces would be nothing similar, moving just slightly from one location to another should change its sound radically.

Wrong again platitudinous one. You really should get up to speed on this rather than blathering on ad infinitum about how you erroneously imagine it might behave. Bromide is apt. :rolleyes: zzzz

It still seems to produce little low bass.

You apparently haven't read the Geddes paper I linked for you, either. Below the transition frequency, multiple subs are required, and their optimum locations rarely coincide with those of the midbass and above in small rooms. The intent is not to compromise the midbass response by having the VLF driver try to produce it.

I get the sense that it would sound worse to me than it measures, at least for the kind of music I prefer to listen to.

RoyC has built a pair over in Mods and Tweaks. You obviously don't want to learn that you might not yet have all the answers, is what, not to mention being too cheap to find out.... :(

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"You apparently haven't read the Geddes paper I linked for you, either. Below the transition frequency, multiple subs are required, and their optimum locations rarely coincide with those of the midbass and above in small rooms. The intent is not to compromise the midbass response by having the VLF driver try to produce it."

How sad for owners of AR1, AR3, AR3a, AR 10 pi, AR LST, and AR 303 that their low bass and mid bass is compromised. Somehow they don't seem eager to trade up to Gedlee. They must be "uneducated."

So where do I hear a pair of these gems in the NY Metro area or are they only sold as kits? Funny, when I asked the same on another blog site about where I could hear Audio Note speakers he raved about, there were no dealers in the NY Metro area, perhaps the most sophisticated, most affluent, and largest single market in the world. When I finally heard them at a trade show, I knew why there were no dealers. There's always a good reason if there isn't.

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