omnidirectional loudspeakers = best design available

[Wesayso]

That Toole quote above was not in reference to choosing one’s speakers to suit one’s music listening tastes, so not on point.

And Toole references Griesinger extensively, so I doubt there are important differences in their views in Griesinger’s specialty subject of spatial effects.

Cheers

So do tell us what the ideal/final DI for a speaker should look like (aside from being smooth). Because as far as I'm aware no definitive answer to that question has been given yet. The intel from Griesinger and Toole doesn't perfectly line up on all counts, as you no doubt know.
Especially about the role of early reflections, a topic that Dr. Geddes and Dr. Toole also didn't see eye to eye on:

I actually am very curious if this is the main reason of a difference of opinion between Dr. Geddes and Toole on the subject of early reflections. Not having heard what they hear in their preferred environment I can only guess at it though.

For the record, I recently talked with Floyd on this exact point. I believe that he has softened his position (although he claims that people misquoted him and that he was never fixed in his opinion on early reflections.) It appears now that he and I both agree that Very Early Reflections (VER) are a compromise. While they add spaciousness, envelopment and enhance ASW, they will degrade imaging on more dry studio type recordings. Floyd now recommends the ability to either have VER or not with adjustable side curtains. Since my listening is almost 100% studio work, I do not see the need to have "options". Floyd is virtually 100% large venue recordings and hence his earlier beliefs that enhanced spaciousness was a major benefit.

So basically this discussion about VER has no real resolution as it entirely depends on what one is looking for and not everyone will be the same. Suffice it to say that if orchestral pieces recorded in a large venue are your goal then you will want wider directivity and/or more reflective side walls. If studio work with precise imaging is your goal then narrower directivity is beneficial to avoid VER without the need for side wall absorption. If your speakers do not have controlled and narrow directivity and you want good imaging then absorptive side walls are probably essential.

Source: https://www.diyaudio.com/community/...eo-phantom-center.277519/page-26#post-4715727

It definitely is something that differs from speaker design to speaker design, namely the DI has a large influence on this very subject as one can read in this quote from Dr. Geddes. I haven't had the chance (yet) to ask Dr. Toole the same question... The papers and presentations from Dr. Griesinger make it clear what his point of view is.

No doubt you can answer this dilemma even better than Dr. Toole himself?

 

[Blumlein 88]

So do tell us what the ideal/final DI for a speaker should look like (aside from being smooth). Because as far as I'm aware no definitive answer to that question has been given yet. The intel from Griesinger and Toole doesn't perfectly line up on all counts, as you no doubt know.
Especially about the role of early reflections, a topic that Dr. Geddes and Dr. Toole also didn't see eye to eye on:




Source: https://www.diyaudio.com/community/...eo-phantom-center.277519/page-26#post-4715727

It definitely is something that differs from speaker design to speaker design, namely the DI has a large influence on this very subject as one can read in this quote from Dr. Geddes. I haven't had the chance (yet) to ask Dr. Toole the same question... The papers and presentations from Dr. Griesinger make it clear what his point of view is.

No doubt you can answer this dilemma even better than Dr. Toole himself?

Maybe he'll answer for himself what the best DI is.
@Floyd Toole

 

[Floyd Toole]

H-m-m-m. What is the "ideal" loudspeaker radiation pattern? For what application? Stereo from the sweet spot? Multichannel? It makes a difference. If spatial presentation is a consideration - and it must be - then the recording itself is a factor. I have not reviewed this thread so I'm just jumping in to an ongoing conversation.

Obviously, it comes down to personal opinions while listening to and through non-standardized recordings in rooms that are undoubtedly not standardized. I doubt that a single answer is possible. Each to his own.

Underlying it all is that stereo - two channel record/reproduction through loudspeakers - is fundamentally flawed. In "live" experience we hear only one direct sound in each ear from a single sound source. In stereo all sound images between the loudspeakers are phantoms, created from identical (mono) sounds with interchannel amplitude or time differences to provide location differences. Each ear receives two versions of the same sound, separated by a delay and modified by head diffraction. Direct sounds arrive from about +/- 30 deg. which provides HRTF characterization for the wrong incident angle - generating an unavoidable timbral error as well as possible localization confusion for familiar sounds. The two time-separated sounds in each ear generate acoustical interference, resulting in an audible dip around 2 kHz (enough to degrade speech intelligibility for the center image - usually the featured artist), and to destroy any notions of pristine waveforms, impulse response, phase response, etc in the direct sounds.

This is the background within which the question is being asked. That there are people who think that stereo is somehow a naturally superior form of reproduction is a testament to human adaptability.

To this background analysis of direct sound must be added the contributions of reflected sounds, and my instincts tell me that there may well be advantages to some added confusion - a sense of spaciousness. Anechoic chamber stereo is not especially flattering. In the years of double-blind listening tests in normally reflective rooms there did seem to be a generalized preference for loudspeakers with well behaved wide dispersion. As many of you may know, listeners were far more critical in their assessments of sound quality when listening to a single loudspeaker. Was this because the spatial confusion and inherent amplitude/phase distortions of stereo were absent? Is this why headphone listening has such an almost magic clarity? One sound to each ear, not two.

Multichannel does not completely solve the problem because there are still phantom images across the front soundstage, but a real center loudspeaker is a start. That delivers "pristine" sound from three locations: center and hard-panned left and right. But the fact that we have adapted to the corrupted sound associated with phantom images remains a confounding factor. I notice that many programs deliver the "center" sound from all three loudspeakers across the front, and some ignore the center speaker. Adaptability is a wonderful feature of human perception.

Good luck in solving the problem. Cheers . . .

 

[Wesayso]

For what application? Stereo from the sweet spot?

@Floyd Toole if I may, can I make the question a bit more specific? I've asked Dr. Geddes and I always wanted to ask you the same thing.
The question raised in this thread was, in a very broad and/or general way, does the type of music the listener prefers have any relation to the preferred DI?
Like Dr. Geddes mentioned when I asked him earlier about 'early reflections' and the difference in opinion between what he prefers and your point of view on it (see quotes a few posts back):

For the record, I recently talked with Floyd on this exact point. I believe that he has softened his position (although he claims that people misquoted him and that he was never fixed in his opinion on early reflections.) It appears now that he and I both agree that Very Early Reflections (VER) are a compromise. While they add spaciousness, envelopment and enhance ASW, they will degrade imaging on more dry studio type recordings. Floyd now recommends the ability to either have VER or not with adjustable side curtains. Since my listening is almost 100% studio work, I do not see the need to have "options". Floyd is virtually 100% large venue recordings and hence his earlier beliefs that enhanced spaciousness was a major benefit.
So basically this discussion about VER has no real resolution as it entirely depends on what one is looking for and not everyone will be the same. Suffice it to say that if orchestral pieces recorded in a large venue are your goal then you will want wider directivity and/or more reflective side walls. If studio work with precise imaging is your goal then narrower directivity is beneficial to avoid VER without the need for side wall absorption. If your speakers do not have controlled and narrow directivity and you want good imaging then absorptive side walls are probably essential.

Incidently, that quote from Dr. Geddes comes from a long thread about the flaw in Stereo you just mentioned, the phantom center perception.

 

[Floyd Toole]

I don't remember Earl Geddes and me ever sitting together listening to the music of our choice - his place or mine. So I don't know his music preferences and I don't think he knows mine. Not that it matters, because that is a totally personal thing. When he says "Floyd is virtually 100% large venue recordings" he is mistaken. I listen to many kinds of music, with a broad preference for the popular repertoire when I devote time to serious foreground listening. Tidal is a rich resource. For decades I have had the good fortune of being able to enjoy the LA Phil in live performance a dozen or more times a year and, all due respect to loudspeakers of any origin or type, I find stereo to be an inadequate substitute. Just sitting in the hall while the orchestra "tunes up" and practices their riffs is a pleasure in envelopment that stereo cannot replicate.

But the opinions of Dr. Toole or Dr. Geddes are just that: personal opinions of two individuals. The results of hundreds of double-blind listening tests are a different thing, and they can definitely add information to a discussion. I wish there was a budget for definitive tests, but the evidence from my own evaluations many years ago indicated that the recording itself was a powerful factor in listener preference. Stereo is not an encode/decode process. There are no standards, just "common practice" and personal tastes of recording engineers and musicians.

But, in the end it I is "your" opinion, of your music, in your room, played at your preferred sound level that matters. I have a personal opinion, it has changed over the years, and frankly at age 84 I not sure you should care what it currently is (smile).

 

[Newman]

No doubt you can answer this dilemma even better than Dr. Toole himself?

Your sarcasm was neither appreciated nor necessary, and I see Dr Toole has done me — and more importantly, the thread — a huge favour in his posts above.

Cheers

 

[BenB]

@Blumlein 88 I think Ben is into crosstalk cancellation arrays, but he should know better than I!

Yes. The current prototype is simply 5 cardioid mics spaced equilly around a unit circle. Post processing will turn this into 10 synthetic channels with far narrower response than cardiod. Any sounds originating from outside the narrow response lobe of each synthetic channel will be drastically reduced, as Blumlein alluded to. All the synthetic channels will have the same acoustic center (behave as if all microphones were colocated). Then those 10 channels can be mixed down to any smaller number of channels. An optional 6th omni microphone can capture bass the same way a mono subwoofer reproduces bass.

 

[Blumlein 88]

Yes. The current prototype is simply 5 cardioid mics spaced equilly around a unit circle. Post processing will turn this into 10 synthetic channels with far narrower response than cardiod. Any sounds originating from outside the narrow response lobe of each synthetic channel will be drastically reduced, as Blumlein alluded to. All the synthetic channels will have the same acoustic center (behave as if all microphones were colocated). Then those 10 channels can be mixed down to any smaller number of channels. An optional 6th omni microphone can capture bass the same way a mono subwoofer reproduces bass.

Thank you.

You may wish to read this paper from J_J. There are a few details which can be puzzled out from multiple other sources. However I think AT&T owns rights to those as J_J seems reluctant to discuss some details. Anyway, perceptual soundfield reconstruction. He uses two extra microphones pointing up and down. There is a simple mix to put that into the 5 channel mix. So 7 microphones total.

https://www.pearl-hifi.com/06_Lit_Archive/02_PEARL_Arch/Vol_16/Sec_53/AES%20109/00081.pdf

 

[Blumlein 88]

Also I guess you are familiar with the Eigenmike.

mhacoustics.com

mhacoustics.com

A paper about one way to use it.

https://etd.lib.metu.edu.tr/upload/12625182/index.pdf

 

[Newman]

But the opinions of Dr. Toole or Dr. Geddes are just that: personal opinions of two individuals. The results of hundreds of double-blind listening tests are a different thing, and they can definitely add information to a discussion. I wish there was a budget for definitive tests, but the evidence from my own evaluations many years ago indicated that the recording itself was a powerful factor in listener preference. Stereo is not an encode/decode prsocess. There are no standards, just "common practice" and personal tastes of recording engineers and musicians.

To me, this is saying that, in answer to the question of certain speaker DI being more suited to certain types of music, the answer is not really, because the variations in recording and mixing and mastering techniques, plus use or non-use or mis-use of spatial effects in the recorded medium, are much bigger and will swamp any correlation between speaker DI and type of music and listener preference. At least, subject to more pointed experimental evidence being made available.

And this means that the speaker DI should/could be chosen for its resilience (or insensitivity) across the many flavours of “recording sound”. And IIRC (and hoping not to put words in your mouth Dr Toole, just trying to summarise for the general readership), the most resilient choice that I have gleaned from your writings seems to be forward facing with wide dispersion for 2-channel playback over two speakers, and less critical for multichannel recordings and playback but with the opportunity to use speakers that are slightly less wide in dispersion but still wide enough to cover the listening area, but not so wide as to bring awareness of the playback room excessively into play.

cheers

 

[AdamG]

I don't remember Earl Geddes and me ever sitting together listening to the music of our choice - his place or mine. So I don't know his music preferences and I don't think he knows mine. Not that it matters, because that is a totally personal thing. When he says "Floyd is virtually 100% large venue recordings" he is mistaken. I listen to many kinds of music, with a broad preference for the popular repertoire when I devote time to serious foreground listening. Tidal is a rich resource. For decades I have had the good fortune of being able to enjoy the LA Phil in live performance a dozen or more times a year and, all due respect to loudspeakers of any origin or type, I find stereo to be an inadequate substitute. Just sitting in the hall while the orchestra "tunes up" and practices their riffs is a pleasure in envelopment that stereo cannot replicate.

But the opinions of Dr. Toole or Dr. Geddes are just that: personal opinions of two individuals. The results of hundreds of double-blind listening tests are a different thing, and they can definitely add information to a discussion. I wish there was a budget for definitive tests, but the evidence from my own evaluations many years ago indicated that the recording itself was a powerful factor in listener preference. Stereo is not an encode/decode prsocess. There are no standards, just "common practice" and personal tastes of recording engineers and musicians.

But, in the end it I is "your" opinion, of your music, in your room, played at your preferred sound level that matters. I have a personal opinion, it has changed over the years, and frankly at age 84 I not sure you should care what it currently is (smile).

Thank you Sir for openly sharing your life experiences with regard to music reproduction. You might be surprised to discover we have a fairly well aged audience. Your comment about changing tastes in music as we age resonates with me and I expect many of us here.

Wishing you and your family a very merry Christmas and a healthy and happy new year!

 

[Duke]

So do tell us what the ideal/final DI for a speaker should look like (aside from being smooth). Because as far as I'm aware no definitive answer to that question has been given yet.

I think the situation ends up being "pick your poison"! Fortunately it comes in many different flavors...

I'm under the impression that when Earl Geddes talks about the detrimental effects of reflections, he is primarily talking about the EARLY reflections. I'm under the impression that he finds the later reflections to be of net benefit, as they do not affect the image precision as much (if at all), while still imparting desirable spaciousness.

Not sure what the exact DI would be, but my poison of choice is of the multi-directional flavor, with a narrow forward-facing pattern toed-in to avoid strong early sidewall reflections, plus a separate complementary pattern aimed well away from the "sweet spot" to maximize its reflection path length, the idea being to minimize early reflections (like a narrow-DI speaker) while still having plenty of later-arriving reflections (like a wide-DI speaker).

... To this background analysis of direct sound must be added the contributions of reflected sounds, and my instincts tell me that there may well be advantages to some added confusion - a sense of spaciousness. Anechoic chamber stereo is not especially flattering. In the years of double-blind listening tests in normally reflective rooms there did seem to be a generalized preference for loudspeakers with well behaved wide dispersion.

Do you have an opinion on whether it was primarily the increased EARLY reflections which tipped preference towards wide-dispersion speakers, or the increased LATER reflections, or both?

(Floyd, my wife just walked by and looked over my shoulder and said, "Oh, hi Floyd Toole"! She hears me refer to you so much that I think she thinks she knows you!)

 

[AdamG]

wife just walked by and looked over my shoulder and said, "Oh, hi Floyd Toole"!

It could have been far worse!

 

[BenB]

Also I guess you are familiar with the Eigenmike.

mhacoustics.com

mhacoustics.com

A paper about one way to use it.

https://etd.lib.metu.edu.tr/upload/12625182/index.pdf

View attachment 249837

Thanks for the links. Looking at the papers, I'm glad my array is of the more "open" variety, with reflections and diffractions predominantly being contained in the attenuated part of the cardioid pattern of each mic. I don't think I'd want to deal with the boundary conditions of a closed spheroid.
I found this ping pong game to be a surprisingly effective demonstration when played back on my headphones:

I suspect AT&T is using hypercardiod mics for the narrowed main beam response, but that would appear to make them more susceptible to reflections and diffractions of sound passing through the array. The original concept of my array had the mics coincident... basically they were all pointing into the circle rather than out of it... it didn't work, because of the distortions caused to the sound waves reflecting and refracting around the mics. Pointing the mics out, I don't have interference problems, but they are non-coincident, which is something I can account for in my processing. What you've shared here makes me more encouraged about the possibilities... but this needs to stay number 2 in my queue for now. Thanks for sharing!

 

[MattHooper]

I don't remember Earl Geddes and me ever sitting together listening to the music of our choice - his place or mine. So I don't know his music preferences and I don't think he knows mine. Not that it matters, because that is a totally personal thing. When he says "Floyd is virtually 100% large venue recordings" he is mistaken. I listen to many kinds of music, with a broad preference for the popular repertoire when I devote time to serious foreground listening. Tidal is a rich resource. For decades I have had the good fortune of being able to enjoy the LA Phil in live performance a dozen or more times a year and, all due respect to loudspeakers of any origin or type, I find stereo to be an inadequate substitute. Just sitting in the hall while the orchestra "tunes up" and practices their riffs is a pleasure in envelopment that stereo cannot replicate.

But the opinions of Dr. Toole or Dr. Geddes are just that: personal opinions of two individuals. The results of hundreds of double-blind listening tests are a different thing, and they can definitely add information to a discussion. I wish there was a budget for definitive tests, but the evidence from my own evaluations many years ago indicated that the recording itself was a powerful factor in listener preference. Stereo is not an encode/decode prsocess. There are no standards, just "common practice" and personal tastes of recording engineers and musicians.

But, in the end it I is "your" opinion, of your music, in your room, played at your preferred sound level that matters. I have a personal opinion, it has changed over the years, and frankly at age 84 I not sure you should care what it currently is (smile).

Hi Dr. Toole!

I have a question which will relate to the subject of speaker blind testing.

When it comes to sound reproduction: "What makes for Good Sound?"

(In terms of what we tend to perceive as "good quality sound")

I'm wondering if we can actually answer this to some degree from data or research, or even if you've drawn your own personal inferences on the subject.

To provide some context for the question:

Some will say any SUBJECTIVE judgement of "good sound" will be so variable as to be useless. (Hence: may as well stick to ideals like "technical accuracy" which are more amenable to objective verification such as measurements). However, we know that preference is often studied in science. And indeed the point of the blind testing research you often cite is that there ARE discernible, reliable trends in what people will rate as "good sound" (expressed as preferences).

Given we have the preference-rating data from blinded studies on speakers, there may be an inclination to say "We can know what makes for Good Sound: Speakers that measure in a particular way (e.g. a Harman Kardon-type curve) are reliably rated for Good Sound. So, there's your answer, it's in the speaker measurements!"

Except of course that can't be the answer. At best it's only 1/2 the equation. The other 1/2 will be in the 'quality'of the recordings themselves. (And it was found recordings themselves influenced the speaker ratings).

If you have a speaker measuring like a Revel Salon 2, but play a recording that has all sorts of frequency peaks and valleys, similar to those that get a speaker design rated as 'poor quality,' then even through the "well measuring speaker" you will get "poor quality sound." So speaker measurements don't tell us what "Good Sound Quality" is per se. The recordings themselves used in speaker tests have to be selected on some criteria of "good sound quality" to begin with. But...then...what is that?


As I understand it, at least some of the recordings used for the blind tests were selected for having some level of "good" sound quality to begin with - e.g. ones that contained more naturally recorded vocals etc.

So if we are asking about some general criteria for "Good Sound Quality," it seems to me that at least ONE aspect is likely to be "sonic realism." If you had one speaker that could reproduce voices and instruments indistinguishable from the real thing, and another that reproduced those sounds with obvious colorations/distortions, it would seem likely that the first speaker would be rated higher for sound quality in blind tests. This would be especially true of the human voice, given our familiarity with the real sound of voices. Even with perfection being impossible, the speaker producing voices "more naturally," without obvious resonances or colorations, will be rated better.

Is this train of thought is correct? That, even though a sound system can not be expected to reproduce sound indistinguishable from live, nonetheless we still tend to have, and use, our experience of "real sound" like voices as one touchstone to rate sound quality?

And also, if there is some other general traits in reproduced sound for what people will rate as "Good Sound," aside from "more natural/more realistic" what might those general traits be, based on your research or personal hunches?

Cheers!

 

[Newman]

but play a recording that has all sorts of frequency peaks and valleys

Isn’t that………..music?

 

[MattHooper]

Isn’t that………..music?

Indeed. But we subjectively rate the sound quality of recordings too, of course.

 

[Newman]

Well I don‘t think we can do that without subjectively judging the music itself.

I mean, if musicians put down 60 minutes of unrelenting thrash metal at top volume and are only satisfied with the production when compressed within an inch of its life, earsplitting treble, suppressed mids and unintelligible (thankfully) vocals, then that’s their art (including the production) and it’s right.

And who knows, it might go into the annals as a serious piece of art in the history of music. Seriously.

So getting a rating of the sound quality of the above recording is actually a rating of the music. It will get a low rating. Not that many people are into it.

A preference rating along those lines already exists: the music sales charts.

If your question is what are the components of that rating as summed in the music sales charts, then you are asking how do we listeners decide what music we like.

So, if that’s not what you are asking, I think your question needs further clarification and distinction so that it doesn’t overlap with the above issue.

cheers

 

[MattHooper]

Well I don‘t think we can do that without subjectively judging the music itself.

I mean, if musicians put down 60 minutes of unrelenting thrash metal at top volume and are only satisfied with the production when compressed within an inch of its life, earsplitting treble, suppressed mids and unintelligible (thankfully) vocals, then that’s their art (including the production) and it’s right.

And who knows, it might go into the annals as a serious piece of art in the history of music. Seriously.

So getting a rating of the sound quality of the above recording is actually a rating of the music. It will get a low rating. Not that many people are into it.

A preference rating along those lines already exists: the music sales charts.

If your question is what are the components of that rating as summed in the music sales charts, then you are asking how do we listeners decide what music we like.

So, if that’s not what you are asking, I think your question needs further clarification and distinction so that it doesn’t overlap with the issue I am raising above.

cheers

No my question isn't answered at all by appeal to music sales. I'm talking about sound quality, not music quality. People can appreciate music on all sorts of devices, from old transistor radios, crappy turntables, laptops or name the "worst measuring" speaker brand you want. Whatever people like musically doesn't help tell us anything about sound quality.

One way to think about my question is to ask yourself: If you wanted to demonstrate your hi-fi system to a non-audiophile, that is show what it can do as opposed to much poorer quality systems most people might be used to, what demo tracks would you select and why?

Personally, I've used various demo tracks over the years. I can put on some recordings - e.g. vividly recorded vocals with light acoustic accompaniment (e.g. some Astrud Gilberto tracks, virtually everyone likes the music) and every time...every single time...the listener is blown away. All rate the sound quality they are hearing as very high. Why? Always the same reaction "It Sounds So Real!!!" Most people never even have an inkling of what a high end system can do in sonic terms, or even think music can "sound realistic" so they tend to be shocked to encounter such sound. (Of course I'm not talking perfectly indistinguishable from live - as Dr. Toole says, stereo is compromised. But certainly "much CLOSER to the real thing" than most people have heard).

So, if you were to show a non-audiophile what your system is capable of...why you have put so much time, attention (and possibly money relative to a non-audiophile) in to it...what type of recordings would you use? Presumably you wouldn't use a horrendous, thin, scratchy recording right? So just think about the general attributes that you think will tend to bring forth a response "that sounds really good." What would those be?

ETA: Apparently Harman has a list of recommended tracks:

Harman Art of Listening Playlist

Playlist · blSwagger07 · 24 items · 149 saves

open.spotify.com

So it would be relevant to ask: is there a general trend in there in terms of why they were chosen, such that they would reveal what people will judge as "good sound?" (I've given my own answers on this before, but I'm interested in Dr. Toole's view, and certainly in yours too Newman).

It's a bit of a philosophical chicken-or-the-egg question. What Makes For Good Sound Quality? You can't say "speakers that measure well" because they won't sound "good" to people if the recordings themselves sound "bad." But then, it can't just be the recording itself: if you play a "good recording" through a "bad speaker" then you'll get "bad sound." So then what is the measure of a "good recording?" For sound reproduction quality, neither appeal to the recording itself, nor the speaker itself, can tell us what Good Sound is. Which implies we have some sort of notion of "good sound when we hear it" criteria. (And at least one viable criteria - maybe not the only - would be "sounds like the real thing." I'm sure there are other touchstones too).

 

[Wesayso]

Your sarcasm was neither appreciated nor necessary, and I see Dr Toole has done me — and more importantly, the thread — a huge favour in his posts above.

Cheers

Indeed he did and I'm thankful for that. It might mean that your task is less needed though. Meaning you don't need to be his spokesperson.
But old habits and all that, I see you're back at making your own interpretation already. That's the part I could do without.