# A Response to Floyd E. Toole's AES Article "The Measurement and Calibration of Sound Reproducing Systems"



## AudiocRaver (Jun 6, 2012)

A Response to Floyd E. Toole's AES Article "The Measurement and Calibration of Sound Reproducing Systems"

Mr. Toole has done much for the audio industry over the years, as is clear from his excellent recent article in the Journal of the Audio Engineering Society, The Measurement and Calibration of Sound Reproducing Systems. Unfortunately, the good Mr. Toole appears to have left an entire class of listeners out of his study altogether - the _Soundstage Listener,_ for whom a natural, lifelike soundstage and precise imaging are a "holy grail" in speaker setup and calibration.

The importance of achieving an _appropriate balance_ between the objectives of having good frequency response (FR) performance and good soundstage and imaging (SS&I) performance is hinted at in section 2.0 (p513), but is terribly under-emphasized. In fact, it is my opinion that this single factor is the thread which, when pulled at to understand its implications, potentially leads to the unravelling of Toole's thesis, that "a calibration methodology that could be applied throughout the audio industry" (abstract) is achievable.

Of course listeners prefer "the delivery of an accurate, neutral, direct sound" (P 538). However this point tends to be used in support of the rule of thumb to _always point the speaker at the listener,_ as is typical of equilateral triangle configurations. While this approach is clearly the best way to get flat FR delivery, it rarely gives good (SS&I) performance for most loudspeakers. In fact, the best SS&I performance with most loudspeakers is achieved with a significant amount of off-axis aiming of the speakers, as much as 15° to 20° or more, usually resulting in noticeable HF rolloff at the listening position (LP).

One might ask why a listener would be willing to live with that kind of FR sacrifice in any listening situation. The answer is simple: With appropriate attention to detail in setting up speakers, SS&I performance can be achieved that is so engaging that it becomes the primary goal of the listening experience, even to the point of the listener being willing to sacrifice FR performance to achieve it.

Not having seen the precise speaker setups that Toole has used in his research, one can only make an educated guess, based upon other information and statements made, that his research and studies have all been conducted with the LP on the speaker axis. 

"Flat on-axis frequency response is clearly the engineering objective for most of these systems." p512
The general discussion on pp515-517.
This is unfortunate. What is implied is that all of the research he has conducted has been under circumstances in which the listeners have been exposed to SS&I performance which, for most speaker types involved, has been less than optimal, perhaps even poor, relatively speaking. It is unfortunate because, in my experience, when listeners are given the choice between flat, even on-axis FR with mediocre-to-poor SS&I performance vs. top-notch, viscerally-engaging SS&I performance with some minor sacrifice in FR, the majority of listeners will choose the setup favoring the SS&I performance every time.

The implications relative to Toole's research are as follows:

The importance of using a loudspeaker that "radiates a flat, smooth, direct sound, and that has gradually changing or constant directivity" (p525) does not change. While the following point has not been researched, it is completely reasonable and likely that these same characteristics would contribute to good SS&I performance. In fact, the "gradually changing or constant directivity" characteristics would support the worthy goal of minimum change in FR when the speakers are aimed away from the LP to get better SS&I.
Beyond that, the direction one would take to calibrate a sound system potentially takes turn _where SS&I are a high listening priority._

The placement and aiming of the speakers is undertaken with SS&I performance being the primary goal, and with no regard for high-frequency rolloff that results from off-axis aiming. This is an entirely by-ear process at this time. It is conceivable that there could be a measurement method which could lead to a good SS&I set up result, but I have yet to see it happen and have tried it numerous times. Even finding a sweet spot with good frequency response matching and good phase matching between left and right speakers in a stereo pair does not seem to be enough to ensure good SS&I performance. Further, that sweet spot that does give good SS&I performance may, when measurements are taken, oddly show less-than-the-best matching between the left and right frequency response and phase measurements, yet still display striking SS&I performance characteristics. This is all due to some relationship between direct and reflected sound paths in a given listening room that gives the hoped-for result, and at this point there is no simple formula that leads to a measurement method that can predict a good SS&I set up. There is no doubt however that several experienced listeners will agree when the goal has been achieved, as I have been among such groups that have set up speakers in that way to achieve SS&I performance day in and day out and always agreed when that sweet spot for SS&I performance had been achieved.
Once SS&I performance has been achieved, then one is left with the question of what to do about the roll-off in the high-frequency response.
One alternative is to ignore it.
Another is to apply automated DRC to compensate for it. As is suggest in Toole's paper, there are limits to what can be achieved without creating undesirable side effects, so less is better here. In general, the application of automated DRC to compensate for the HF variations under these conditions has been found to be beneficial.
The third alternative is to use simple minimum phase filtering, a single band HF shelf filter, for instance, to boost or smooth frequencies equally between the left and right speaker to achieve the flattened frequency response that is desired.
All three of these alternatives have been applied very satisfactorily. That high-frequency roll-off can be quickly tuned out in the listeners mind, and after a few minutes of listening forgotten about altogether. This is not to say that flatter frequency response would not be preferred, but simply to say that some degree of HF roll-off is easily tolerated where the means to correct it is not readily available.

Mr. Toole is to be applauded for his goal and the marvelous research that he has undergone over the years toward achieving it. Few have the patience and focus to accomplish what he has. But to leave out of his study altogether the pickiest type of listener of all seems a major oversight. It is clear that to include them (us) complicates his work immensely. It would be folly to suggest that he has overlooked us on purpose. Yet we are not an invisible contingent - although admittedly our numbers might not be impressive, they grow steadily as the word gets out.

If it turns out that we are somehow included in that study with full consideration for our seemingly very different setup and calibration goal, then I will apologize. If such is the case, however, one would think its mention would be more easily recognized, and that it would receive more than the cursory coverage given in section 2.0 (p513).

I for one will be curiously watchful of Mr. Toole's future writings and research to see how he includes this group in his research and in the "Unified Calibration Method" he is seeking to achieve.


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## Lumen (May 17, 2014)

Thanks for bringing this article to our attention, Wayne, and for your keen observations. Dr. Toole is, indeed, a researcher extraordinaire. I've followed his publications and activities with great interest both before and after purchasing the original Revel Salon speakers. A few of his writings are listed here. As a scientist he naturally leans toward the objective, but recognizes that objective design alone fails to satisfy discriminating listeners (of SS&I) which have one foot on the subjective side. Purely objective design also tends to ignore human preferences (i.e. flat response is not pleasing to the ear). But how and what to measure? Dr. Toole again hints at, but doesn't elaborate on, spatial psychoacoustic SS&I phenomena in his paper Audio Science in the Service of Art:

"To design audio products, engineers need technical measurements. Historically, measurements have been viewed with varying degrees of trust. However, the value of measurements has increased dramatically as we have found better ways to collect data, and as we have learned how to interpret the data in ways that relate more directly to what we hear. With measurements we can set objectives, telling us when we are successful. Some of these design objectives are very clear, and others still need better deﬁnition. All of them need to be moderated by what is audible. Imperfections in performance need not be immeasurably small, but they should be inaudible. Achieving this requires knowledge of psychoacoustics, the relationship between what we
measure and what we hear."

Another passage taken from the same paper seems to support SS&I listeners comprise a significant portion of the listening community: "...all sound radiated by a loudspeaker, in whatever direction, eventually reaches the listener, and all of it will influence what we perceive in terms of sound quality _and spatial and directional effects._" (my emphasis).

I think the doctor's focus is on objective data, and on pleasing his colleagues in the AES. Trying to convince them of unmeasurable psychoacoustic phenomena is not on his agenda.


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## AudiocRaver (Jun 6, 2012)

It doesn't help that there is no clearcut way to measure for successful SS&I implementation, nor a truly clearcut way to set it up - _DO THIS and you will get a great soundstage._

There are those who deny it exists, but get a group of experienced listeners in a room and they will agree when it is right.


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## FargateOne (Mar 3, 2015)

AudiocRaver said:


> A Response to Floyd E. Toole's AES Article "The Measurement and Calibration of Sound Reproducing Systems"
> 
> (...)
> 
> ...


I totally agree with you. Since I deserted the "sacro-saint" rule of the equilateral triangle (religiously applied since 40 years in my case!):rubeyes:, a couple of weeks ago, my listening experience with my HT *and* my stereo system for musik is so much more satisfactory.:bigsmile:



> One might ask why a listener would be willing to live with that kind of FR sacrifice in any listening situation. The answer is simple: With appropriate attention to detail in setting up speakers, SS&I performance can be achieved that is so engaging that it becomes the primary goal of the listening experience, even to the point of the listener being willing to sacrifice FR performance to achieve it.


You bet ! When you are watching a movie and you can pinpoint the trumpet or the piano of the soundtrack and hear clearly the dialogue ...what a trip !:sn:

Of course there is always place for FR improvement too.


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## Jon Lane (Oct 9, 2010)

Kudos for one of the better thoughts on sound I know I've read in a long time, Wayne. I've used a 3:4 triangle for over 30 years...

Interestingly, SS&I is terribly important, but it could be that its presence is itself an indicator of other behaviors not found in conventional wisdom or the usual vernacular, and impossible to locate in the objective data. 

_There are those who deny it exists, but get a group of experienced listeners in a room and they will agree when it is right._

As many of us have said - even if mostly privately - there's good hifi and then there's the undeniable illusion of real music. The difference is neither subtle nor predictable by the usual methods.


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## dgmartin (Oct 29, 2011)

You are certainly touching the limitations of the current psychoacoustic science. I'm certain someone like Floyd Toole has his own ideas about SS&I but as a scientist he needs to gather data to prove it with statistical evidence before he can publish anything. 

In my opinion the challenge in developing a clearcut way to setup and measure for optimal SS&I lies in the listener preferences (some value timbre more than spaciousness and vice-versa). Even when listener preferences were compiled, it will be difficult to achieve without previously developing recording standards since the listener preferences will vary with recording material.

I'm sure you all read that once also but IIRC the widely accepted metrics were imaging and spaciousness/envelopment and he seemed to present them as somewhat tradeoff since the former is improved by absence of reflection while the latter is provided the reflections. As you mentioned there is the FR on top of that. 

About the setup, audiophiles and hi-fi shops have aimed speakers straight ahead or so for as long as I can remember whereas studio speakers followed the old triangle rule. This is in-line with their respective objectives (plus many “hifi” designed are unbearable on-axis).

Have you tried the positioning method of Earl Geddes, that is more toe-in to remove early reflection (good for timbre+imaging)? That way you are also listening off-axis and the reflections contribute to the spaciousness but being delayed they do not harm timbre+imaging as much as when the speakers are aimed straight. His approach implies constant directivity speakers like his to keep good FR off axis as well but I have found it worked well even with conventional cone+dome speakers.

@Lumen thanks for the AC link, I had all the files on PC but wanted to share it with a friend.


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## lcaillo (May 2, 2006)

Having worked with Wayne many times positioning speakers, I can tell you that he has tried such positioning, along with many others. He rules out very little as possibilities, and we have tried some pretty outrageous things. My experience is that he rarely fails to end up with what I personally would, because we seem to prioritize similar sound. I think it would be possible to isolate SS&I scientifically, but it would be a tedious matter and would involve some pretty boring listening tests. 

Perhaps in the next sessions that we have we can do some blind speaker positioning tests to see if we come up with the same conclusions with respect to position and direction.


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## AudiocRaver (Jun 6, 2012)

I would be happy if we could do some blind tests that simply showed that we all agreed when the soundstage and imaging were at/near optimum.


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## ajinfla (May 10, 2009)

Hi Wayne,

Just caught this thread. I have no idea how what you said has anything to do with the Toole paper, which is mainly about EQ/so called "room correction" products. What am I missing here?



AudiocRaver said:


> I would be happy if we could do some blind tests that simply showed that we all agreed when the soundstage and imaging were at/near optimum.


You might as well do a blind test for optimum tasting beer.
"Sounstage and imaging" is going to be a preference test, no more, no less.
Hopefully you grasp that the S&I begins for most part (rare exceptions of true live multi-mic recording), with a wholly artificial construct in a production studio, based on ILD and ITD developed from the days of Blumlein. I really wish most audiophiles could go to a studio to see how things are "constructed" spatially, but unfortunately, 99.999% do not.
So now we have our electrical construct media that we must now reconstruct to our pleasure. That involves those particular speakers/3D polar response, that particular room, the recording...and that particular listeners personal preference. There is no "optimum", other than the listeners preference, for what they believe is optimum.
IOW, things Toole wisely knows comes down to things well beyond just the loudspeakers....and outside his scope.

Btw, the top Revel does not have extremely wide/flat horizontal dispersion by accident.








That particular feature is there for reasons...one being very much related to S&I. I really think Harmans research (based on NRC/Toole/Olive et al) is more misunderstood than understood to the casual eye.

cheers,


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## AudiocRaver (Jun 6, 2012)

ajinfla said:


> Hi Wayne,
> 
> Just caught this thread. I have no idea how what you said has anything to do with the Toole paper, which is mainly about EQ/so called "room correction" products. What am I missing here?


All due respect, I pretty much predicted your response.

I will (re)summarize:

Toole is "seeking a calibration methodology that could be applied throughout the audio industry." (abstract)
Toole's research assumes (this is easily inferred from the text of his paper) that an on-axis listening position (LP) would be universally preferred.
On-axis LP _usually_ gives poor SS&I. This depends upon the design of the speaker and the upon the room.
Setup, measurement, and calibration methods are different for the audience that prioritizes SS&I highly. There is an entire listening audience that has been ignored in his research. His "universal calibration methodology" is almost certain to overlook most of the more particular listeners on the planet.



> You might as well do a blind test for optimum tasting beer.
> 
> "Sounstage and imaging" is going to be a preference test, no more, no less.


I completely disagree. My experience has shown that the difference between good SS&I vs. poor SS&I is quite recognizable by the general listener - once he has been exposed to both and given the opportunity to experience a truly top-quality soundstage with sharp imaging, and most listeners have not had that opportunity.



> Hopefully you grasp that the S&I begins for most part (rare exceptions of true live multi-mic recording), with a wholly artificial construct in a production studio, based on ILD and ITD developed from the days of Blumlein. I really wish most audiophiles could go to a studio to see how things are "constructed" spatially, but unfortunately, 99.999% do not.


I grasp it quite clearly, I have worked in multitrack studios since my teens, I have recorded, mixed, mastered, and am sitting in my personal recording studio as I write.



> So now we have our electrical construct media that we must now reconstruct to our pleasure. That involves those particular speakers/3D polar response, that particular room, the recording...and that particular listeners personal preference. There is no "optimum", other than the listeners preference, for what they believe is optimum.
> IOW, things Toole wisely knows comes down to things well beyond just the loudspeakers....and outside his scope.


Toole has gone to great lengths to "prove" that listeners _prefer_ "the delivery of an accurate, neutral, direct sound" (P 538). I am simply stating that there is another _class_ of preference which most of those listeners have not even been exposed to, and that it makes a difference to the conclusions of the research they have done.



> Btw, the top Revel does not have extremely wide/flat horizontal dispersion by accident.
> 
> 
> 
> ...


And perhaps to the experienced as well.

There is no doubt their work holds great value. But it is not the be-all end-all that many claim it to be. Listener preference is what their work is ALL ABOUT! To claim to define listener preference while ignoring a whole area of listener preference that is closely related is a big miss of the _listener preference_ mark, in my opinion.

And I totally agree that the speaker design characteristics you mention are desirable.

If I might, I will simply state that SS&I, while more difficult to measure via instrumentation than frequency response, is not difficult for a listener to recognize. I have seen it time and again, heard reactions, gotten positive feedback to setup suggestions - when the SS&I experience is achieved, it is almost universally applauded. And the same characteristics are almost universally preferred. That has been my experience. Has it been researched with double-blind study? No. I have not had the opportunity. But Toole and all have. And they have apparently chosen to overlook it.

A.J. - I appreciate your response, and while your views are clearly as valid as mine, we are not in agreement on a number of key points. Rather than have this turn into a sparing match, I suggest we agree to disagree and move on. You are, of course, more than free to open a thread to express your own views.


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## ajinfla (May 10, 2009)

AudiocRaver said:


> Toole is "seeking a calibration methodology that could be applied throughout the audio industry." (abstract)


Right, spectrally, recordings are all over the place. Too much bass, too little, bright, dull, etc. I think we've all experienced that.



AudiocRaver said:


> Toole's research assumes (this is easily inferred from the text of his paper) that an on-axis listening position (LP) would be universally preferred.


Regarding spatial reproduction specifically? Please quote that directly, for no ambiguity, thanks.



AudiocRaver said:


> On-axis LP usually gives poor SS&I.


Supporting evidence? I'm an AES member and can access any paper. I can't recall any like that.



AudiocRaver said:


> This depends upon the design of the speaker and the upon the room.


If you mean what affects SS&I, then of course. We agree. How does Toole diverge here?



AudiocRaver said:


> Setup, measurement, and calibration methods are different for the audience that prioritizes SS&I highly. There is an entire listening audience that has been ignored in his research. His "universal calibration methodology" is almost certain to overlook most of the more particular listeners on the planet.


I have no clue how you have concluded this from any Toole paper. Direct quotes would be helpful.
As someone who designs speakers, specifically to vary spatial reproduction aspects, I see absolutely nothing in Tooles work which I've followed for 20+ years, to warrant any such assertion.



AudiocRaver said:


> I completely disagree. My experience has shown that the difference between good SS&I vs. poor SS&I is quite recognizable by the general listener...


That _is_ a preference!
Just like Toole has found most prefer smooth rather than ragged on axis FR, off axis FR, smoother amplitude bass, etc, etc.. *Prefer*. What are you disagreeing with??:huh:



AudiocRaver said:


> I grasp it quite clearly, I have worked in multitrack studios since my teens, I have recorded, mixed, mastered, and am sitting in my personal recording studio as I write.


Great, so you know that there is no standard, for placing the drummer back left 2', 3' or 4' in the SS, yes? So when you playback/listen to a recording you _didn't_ do, is the drummer supposed to be 2', 3', or 4' back? Which is "better"? Or is it just what you prefer?



AudiocRaver said:


> Toole has gone to great lengths to "prove" that listeners prefer "the delivery of an accurate, neutral, direct sound" (P 538). I am simply stating that there is another class of preference which most of those listeners have not even been exposed to, and that it makes a difference to the conclusions of the research they have done.


If you are taking exception to them now preference testing only in mono (vs stereo), especially your favorite MLs, then you could simply have said so. *I agree*! I have raised this issue (and others) with Sean Olive directly. But what that has to do with the Toole EQ paper you seem to be responding to, I have no idea.

I think we may agree far more than you think, but I just don't see the connection to the Toole paper referenced. 
See you at the next party.

cheers


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## AudiocRaver (Jun 6, 2012)

ajinfla said:


> Right, spectrally, recordings are all over the place. Too much bass, too little, bright, dull, etc. I think we've all experienced that.
> 
> Regarding spatial reproduction specifically? Please quote that directly, for no ambiguity, thanks.


"Flat on-axis frequency response is clearly the engineering
objective for most of these systems. Those that deviate
significantly earn lower ratings in double-blind subjective
evaluations. Although there is more to be considered, a
flat direct sound delivered to listeners is the basis for most
reproduced sound."
p512



> Supporting evidence? I'm an AES member and can access any paper. I can't recall any like that.


Direct experience with hundreds of speakers. The exception is the horn-loaded mid/tweeter with high directivity.



> If you mean what affects SS&I, then of course. We agree. How does Toole diverge here?


He does not.



> I have no clue how you have concluded this from any Toole paper. Direct quotes would be helpful.
> As someone who designs speakers, specifically to vary spatial reproduction aspects, I see absolutely nothing in Tooles work which I've followed for 20+ years, to warrant any such assertion.


Already stated as clearly as I know how. Nowhere does he mention off-axis listening angles. Nor does he mention soundstage/imaging more than in passing. The two are connected. If they were considered important in his research, it seems he would say so. If you have seen him say so, please show me where.



> That _is_ a preference!
> Just like Toole has found most prefer smooth rather than ragged on axis FR, off axis FR, smoother amplitude bass, etc, etc.. *Prefer*. What are you disagreeing with??:huh:


Argumentative.



> Great, so you know that there is no standard, for placing the drummer back left 2', 3' or 4' in the SS, yes? So when you playback/listen to a recording you _didn't_ do, is the drummer supposed to be 2', 3', or 4' back? Which is "better"? Or is it just what you prefer?


Very argumentative.



> If you are taking exception to them now preference testing only in mono (vs stereo), especially your favorite MLs, then you could simply have said so. *I agree*! I have raised this issue (and others) with Sean Olive directly. But what that has to do with the Toole EQ paper you seem to be responding to, I have no idea.


""


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## ajinfla (May 10, 2009)

AudiocRaver said:


> "Flat on-axis frequency response is clearly the engineering
> objective for most of these systems. Those that deviate
> significantly earn lower ratings in double-blind subjective
> evaluations. *Although there is more to be considered, a
> ...


He's stating the obvious that has been confirmed by others as well. If the system is spectrally chaotic, starting in the studio, exactly how can there be any standardization spectrally?
Are you arguing for SS&I "standards" that Toole is somehow neglecting?? When you just said it will depend on a host of variables, room, speaker directivity...and preferences?



AudiocRaver said:


> Direct experience with hundreds of speakers. The exception is the horn-loaded mid/tweeter with high directivity.


That is very different from Toole et al work and unrelated to the limitations of steady state measurements and so called "room correction"/EQ, _the topic of the paper_. I think your criticism of _this_ paper is misdirected and should be aimed more at their loudspeaker ranking method, using mono, which would put you on firm ground imho and in agreement with myself and others.



AudiocRaver said:


> Already stated as clearly as I know how. Nowhere does he mention off-axis listening angles. Nor does he mention soundstage/imaging more than in passing. The two are connected. If they were considered important in his research, it seems he would say so. If you have seen him say so, please show me where.





> *2 SOUND FIELDS IN ROOMS*
> 
> Sounds arriving at a listening location include charac-
> teristics that are traceable to the sound source (e.g., spec-
> ...


What exactly do you want Toole et al to test/standardize for, with what speakers, in what room, to determine what you will prefer with all your senses, in your room, with your preferences?

cheers,


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## lcaillo (May 2, 2006)

AJ, I think you miss the point. When Wayne is optimizing SS&I it is not some attempt to find a magical state where the "performance" is most perfectly trasmitted to onesperception. It is simply an attempt to find the placement that gives the overall best impression of creating a sound space in which performers are playing music. Certainly it is not a characteristic of the recording alone, nor is it a characteristic of any single component. In a given room with a given system, however, one tries to achieve the best possible experience of the music, which for many of us is improved when a sense of space is perceived.

To suggest that testing of perception is pointless is a revelation of the very limited perspective from which you operate. Wayne, and the rest of us, have always been willing to challenge our assumptions about what we experience. We are quite compfortable negotiating the space between the objective and the subjective. Toole and others have avoided that space by lumping all perception into a notion of preference. What Wayne has attempted to do is to take one aspect of the listening experience and focus on optimizing it to maximize his enjoyment, because it is the part of his own listening preference that appears to be the biggest variable. I tend to agree to a large extent. It is likely that Toole's conclusions about off axis response align with Wayne's experience and views on the matter. The difference is that he never really addressed the matter, that I know of.

One of the most important things about the way we interact here at HTS is that we truly read for understanding, trying to get what others are trying to say, rather than trying to pick apart the words of others to advance our own perspective. You don't have to agree, in fact the very reason that you and Wayne are on staff is that you bring a differenct and valuable perspective to the table, but you sometimes come very close to ridicule, which is not helpful. Please keep that in mind. Challenge, always. Belittle, never.


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## jtalden (Mar 12, 2009)

RE the subject paper:
With the discussion here I was motivated to revisit the paper to try to clarify my understanding. The conclusions were not stated in a way that I found easy to follow. Toole indicates there are other issues and more work to consider. That is why a more definitive finding was not offered. Nevertheless, I tried to pull out and simplify the main points that were made to see if they help this hobbyist's understanding. Since I assembled this for me, I decided to share it here. Feel free to correct me. I hope didn't overlook something important.

Regarding theaters and dubbing stages:
> Flat direct SPL response of the speaker is necessary.
> Smooth controlled speaker directivity is necessary.
> It is not possible to infer a flat direct sound response based on the steady-state room response.
> The LF below approximately 300Hz needs to be EQed to smooth the SPL irregularities due to room modes.
> No other EQ is necessary. [Possibly there is room for gentle EQ shaping to the preferred house curve.]
> The steady-state SPL response will fall several dB starting from 50Hz to ~2kHz as a function of room reflectivity and speaker directivity. 
> Per Fig 14, trained listeners prefer a steady-state house curve which slopes down ~9dB from about 50Hz to 13kHz and then falls a little faster to 20kHz.
> The X-Curve is flat from 50-2k Hz and then drops about 9dB from 2kHz to ~13kHz 
> The X-Curve therefore differs significantly from the preferred curve.
> There is no need for adjustments to a house curve due to venue size. 
> More work is needed before any specific changes to the X-curve or EQ practices can be recommended.

I was not able to pullout much of interest specifically regarding home theater and music rooms except a hint that it may be possible to establish a unified standard that works for all. Wouldn't that be nice!

This doesn't help much to those of us who are looking for a deeper understanding to improve our personal home listening experience. It does reinforce the directional advice that is often given and cites significant data and detail to help with the understanding of it.


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## ajinfla (May 10, 2009)

lcaillo said:


> AJ, I think you miss the point. When Wayne is optimizing SS&I it is not some attempt to find a magical state where the "performance" is most perfectly trasmitted to onesperception. It is simply an attempt to find the placement that gives the overall best impression of creating a sound space in which performers are playing music. Certainly it is not a characteristic of the recording alone, nor is it a characteristic of any single component. In a given room with a given system, however, one tries to achieve the best possible experience of the music, which for many of us is improved when a sense of space is perceived.


Leonard, I haven't missed that the Toole paper is about room/EQ measurements. How is Waynes spatial desires a "response" to a paper about EQ/measurements?
If he had wrote a response to Harmans specific method of ranking speakers via mono tests, then I could see his point...*and agree*.



lcaillo said:


> When Wayne is optimizing SS&I it is not some attempt to find a magical state where the "performance" is most perfectly trasmitted to onesperception. It is simply an attempt to find the placement that gives the overall best impression of creating a sound space in which performers are playing music. Certainly it is not a characteristic of the recording alone, nor is it a characteristic of any single component. In a given room with a given system, however, one tries to achieve the best possible experience of the music, which for many of us is improved when a sense of space is perceived.


Right. Where have I disagreed?



lcaillo said:


> To suggest that testing of perception is pointless is a revelation of the very limited perspective from which you operate.


That's a strange accusation given that I operate based nearly entirely around perceptual *testing*, of the scientific variety, not ad hoc purely personal experience.



lcaillo said:


> Wayne, and the rest of us, have always been willing to challenge our assumptions about what we experience. We are quite compfortable negotiating the space between the objective and the subjective. Toole and others have avoided that space by lumping all perception into a notion of preference. What Wayne has attempted to do is to take one aspect of the listening experience and focus on optimizing it to maximize his enjoyment, because it is the part of his own listening preference that appears to be the biggest variable. I tend to agree to a large extent. It is likely that Toole's conclusions about off axis response align with Wayne's experience and views on the matter. The difference is that he never really addressed the matter, that I know of.


Toole may or may not, but it is certainly not the focus of _this_ paper. Hence my involvement in the thread, _having read the paper_. I've now stated several times that had Waynes criticism been of other aspects of Tooles work, we would probably be _in agreement_.



lcaillo said:


> One of the most important things about the way we interact here at HTS is that we truly read for understanding, trying to get what others are trying to say, rather than trying to pick apart the words of others to advance our own perspective. You don't have to agree, in fact the very reason that you and Wayne are on staff is that you bring a differenct and valuable perspective to the table, but you sometimes come very close to ridicule, which is not helpful. Please keep that in mind. Challenge, always. Belittle, never.


I know Wayne well enough to pick up the phone and call him to clarify any position and I certainly wouldn't belittle him. But I _will_ defend the scientific method that I try to operate under, as long as I can post here.

cheers,


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## ajinfla (May 10, 2009)

jtalden said:


> Regarding theaters and dubbing stages:
> > Flat direct SPL response of the speaker is necessary.
> > Smooth controlled speaker directivity is necessary.
> > It is not possible to infer a flat direct sound response based on the steady-state room response.
> ...


Not much to disagree with there. Toole is simply pointing out the complete lack of standards in the "circle" if you will, beginning at the recording stage. He also points out the limitations of some of the so called "room correction" products being used by (Home) consumers, who are often trying to "fix" erratic 3d acoustic sources with 2d electronic "correction".
No amount of speaker positioning for spatial reproduction preferences, is going to correct anomalies in the onset or direct response of the system, simply based on the way human hearing works.

cheers


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## AudiocRaver (Jun 6, 2012)

AJ,

I appreciate your initial questions because they forced me to think through my remarks and make sure they were presented as clearly as I could present them. I enjoy a good open discussion, but unfortunately we have somehow reached a point of pointless arguing. All due respect, your latest round of comments has pretty much missed my meaning altogether. I enjoy a good discussion, but I think we're at the point of pointless arguing, & I choose not to engage. Thanks again for your initial remarks and questions.


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## ajinfla (May 10, 2009)

No problem Wayne. When either you or Leonard get a chance, read starting from here to see how much we actually diverge on your point of contention, rather than this Toole EQ/measurements paper.

cheers


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## AudiocRaver (Jun 6, 2012)

jtalden: Thank you for an excellent summary. I thought I read a _little_ bit more into the part about room EQ:


If desired objectives are not achieved because of poorly controlled speaker directivity, _get better speakers._ "Equalization cannot change loudspeaker directivity; the remedy is a better loudspeaker."(p516)
Room EQ is of limited value, is generally useless in correcting for speakers with poorly controlled directivity. "Equalization is very limited in what it can “correct,” yet the notion that changing the signal supplied to a sound system consisting of an unknown loudspeaker in an unknown room can “equalize” or “calibrate” a system is widespread."(p517)
Of course there is no argument with either of these points in theory, they are well proven and completely logical. In practical terms, many a listener with imperfect speakers in his home listening environment and on a limited budget has resorted to room correction to try to get some level of improvement in performance, sometimes successfully, sometimes not. I would suggest that a better way to put these points for such a listener would be:

Do not correct too much. Less is usually better.
Do not expect too much in terms of improvement. There is only so much that can be accomplished and negative side effects are quite possible. Room correction might actually give a flatter measured frequency response that sounds worse.
Consider room treatment, and possibly better speakers, rather than sinking a lot of money into room correction.
If you must perform room correction, do some room treatment first. If done correctly, negative effects the speaker's directivity characteristics will be minimized and room correction results will be more effective.
I have no disagreement with Toole on these points as he has stated them. My only reason for the "softened" stance is that well-meaning givers of advice can be extreme in stating that "room correction is a complete waste, Toole says don't waste your time," (paraphrasing from memory, of course). The world is seldom so black and white, it seems appropriate to add a few gray tones to that particular picture.


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## AudiocRaver (Jun 6, 2012)

It has been strongly hinted that my views are primarily based on personal experience in disregard of the scientific method and properly conducted studies.

I will state simply:

I have high regard for the hard-working researchers in the audio industry and their work to further our understanding of acoustics and psychoacoustics for our benefit.
I appreciate the importance of basing my own work and experiments on well-founded principles.
Few have the luxury of conducting double-blind studies to prove every statement we make. Yet we are fortunate to live in a time and part of the world where phenomenal resources are within reach of anyone who wishes to contribute to the stretching of the limits of our understanding of the state of the art.
It is all about sound. In the end, our ears are an important instrument which must be included in the experiment.
Ears are fallible. Imaginations are powerful. Any individually-derived conclusion must be scrutinized relative to proven facts.
I am not afraid to disagree with an industry expert if I believe he has missed an important point in his research or in the advice given based on that research. There is as much danger (that is a strong word in this context) in over-agreeing with and over-generalizing the results of a study as there is in ignoring them. I am making no personal accusation here, simply stating a trend I have observed over time, and my reason for responding to Toole's paper in the first place.
There is very little (none?) of the detail in Toole's paper that I disagree with. Only that his hoped-for "calibration methodology that could be applied throughout the audio industry" (abstract) appears to disregard a critical slice of the high-end listener pie.


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## jtalden (Mar 12, 2009)

AudiocRaver said:


> jtalden: Thank you for an excellent summary. I thought I read a _little_ bit more into the part about room EQ:
> 
> 
> If desired objectives are not achieved because of poorly controlled speaker directivity, _get better speakers._ "Equalization cannot change loudspeaker directivity; the remedy is a better loudspeaker."(p516)
> Room EQ is of limited value, is generally useless in correcting for speakers with poorly controlled directivity. "Equalization is very limited in what it can “correct,” yet the notion that changing the signal supplied to a sound system consisting of an unknown loudspeaker in an unknown room can “equalize” or “calibrate” a system is widespread."(p517)


Points well made. I think we are in basic agreement.
I am use to hearing those 2 bullets as basic rote from what seems like most all speaker manufacturers. I am not sure why they stress those points so hard with all the evidence that full range EQ can be very helpful in many cases. Harmon developed and sells full range EQ devices (I think) so that makes such firm statements puzzling.

In my personal case I EQ full range manually with marked success. I have backed off to achieve flat direct speaker output similar to the guidelines in the paper several times in the past to try to find the improved sound quality that is promised; no success so far. My preferred overall steady-state house curve though is very close to the curve that the experienced listeners prefer in the paper. That target works well for me. The response above maybe 800Hz is fine when the speakers are EQed flat so using direct sound speaker output as flat there is no issue for me assuming some additional EQ roll-off can be applied if needed to meet the LP steady-state house curve. My inclination is though that the target LP response is more important than a flat speaker output in the midrange.

My issue is in the midrange 300 to 800Hz. The most notable issue in that area is that both the FL and FR LP responses have a significant sag around 350-500Hz which is a room effect and not the result of floor or ceiling reflection or any other reflection point I have been able to identify. If I don't boost this range I loose significant information that reduces sound quality. The phone ringing in; 'Why don't you call me any more' by Alicia Keys, is almost completely lost as one obvious example. The boost brings up the SPL, but does it at a 20 ms delay. I hear no ill effect from this late arriving sound, but maybe 'experienced' listeners would on some material. 

As a result of my limited experience; my take would be that; after taking all the measures possible within the imposed constraints regarding the room size/shape, speaker and LP location, and room treatments then it is worth full range EQ experimentation. It may not help, but there are a huge number of testimonials on the web from users of commercial automated EQ systems that suggest that, if done well, it can significantly help in many cases. I would agree that the sound quality may be better (at least theoretically) if the setup was adjusted better to avoid the root cause of issues if possible. Many of us have significant setup and room constraints that limit what we can do in that regard however. Possibly the opponents of full range EQ just lump all these situations into a basket labeled 'bad setup' and discount them? Probably not, but I wish I understood the real situation in that regard.

Regarding this paper I would be tempted to attribute at least some the difference to the narrower and more controlled dispersion of the horn based speakers commonly used. I think Toole did mention however that similar results are achieved using typical domes in home theaters so…

Below is a FL wavelet using my preferred EQ with a filter providing; +5.5dB, 401Hz, 4.5Q. The direct sound is boosted that amount in that range. The result is that the SPL dip at the LP is filled 20ms late. My FR EQ is identical.


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## Audionut11 (Sep 23, 2013)

jtalden said:


> Possibly the opponents of full range EQ just lump all these situations into a basket labeled 'bad setup' and discount them?


My understanding is that Mr. Toole targets an ideal world. This seems ideal since content creators and cinemas should have the funds available to reach this ideal world.

He brushes over home theaters, and I agree with his sentiment here also. Those of us who have been "playing" DSP for years, still don't have a clear understanding of all of the variables. I personally have spent a significant amount of time on research and practice, and I still learn new things all the time (part of the joy for me). And yet, we expect those with little understanding of _any of the variables_ to jump in head first into DSP. Sure, as our collective knowledge increases, and with the help of commercial solutions, the situation probably isn't anywhere near as dire as it once was, but still, if Mr. Toole is nudging people (those I guess who otherwise don't know or don't care) away from DSP, and towards improved playback equipment, and/or room design, surely this is a good thing.

On the subject of "SS&I", there are so many variables, is it really any wonder why no one has attempted significant research? 

For best SS&I, your speakers should have this directivity pattern, with this amount of toe-in, placed this distance from side walls, that have this amount of absorption. If the absorption of the walls is less, you should change toe-in by this amount. If the speakers are placed further from the walls, you should change toe-in by this amount, etc, etc (so many variables). Do we really want to go there? Still, to this day, the industry can't even decide on a correct calibration level ffs.


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## AudiocRaver (Jun 6, 2012)

jtalden said:


> Harmon developed and sells full range EQ devices (I think) so that makes such firm statements puzzling.


I forgot about that. Yes, JBL's ARCOS system is full-range, based on PEQ, not IR filters. Their justification is probably that it is part of the JBL Synthesis pro line, and the speakers in that line are all controlled-directivity (horn) designs, so there is some degree of alignment with Toole's recommendations.



> In my personal case I EQ full range manually with marked success.


My current setup includes Dirac Live, and I have done a fair amount of reflection control and setup optimization beforehand, so DL does not have to correct a huge amount. Switching it in/out, the difference is noticeable but not strong. I think of it as more of a polishing tool - FL & FR frequency response matching is tightened so imaging sharpens nicely.

I have hand-tuned full range for years, always finding the result to be a great improvement. Again, the amount of change was never much, usually cuts only.

Any auto EQ I have heard in fairly well-treated rooms has been an improvement.



> My preferred overall steady-state house curve though is very close to the curve that the experienced listeners prefer in the paper.


As does mine. I end up with about 2 dB of boost from 120 to 30 Hz, about 2 dB of rolloff from 5 kHz to 10 kHz, and I throw in a 1 dB presence peak - or to be more accurate, I _allow_ that peak, which is already there in the speakers - at around 2 kHz.



> I have backed off to achieve flat direct speaker output similar to the guidelines in the paper several times in the past to try to find the improved sound quality that is promised; no success so far...
> 
> My inclination is though that the target LP response is more important than a flat speaker output in the midrange...
> 
> ...


In a bad room with bad (poorly controlled directivity) speakers, it seems logical that the promised _improvement_ of not EQing might be more obvious. Most who are interested in discussing such matters already have pretty good rooms and speakers, so they end up falling into the exception category. I think this is worth noting, that on a relativity scale there are no doubt clear examples that would illustrate the bad effects from room EQ that Toole suggests, but they are probably in situations horrific enough that a more experienced ear would turn and run away rather than try to EQ. The traveling front-of-house sound reinforcement mixer probably has to deal with this more, although FOH arrays tend to be designed for some degree of controlled directivity, as you suggest, so once again the technology leans in the direction of falling into the exception bucket where a smidge of EQ helps more than it hurts. I regularly visit a number of clubs in Lincoln/Omaha to hear live bands, and all have remarkably good sound, most with small vertical arrays. The trend for decent in-house sound in clubs over the last 20 years is definitely good news for touring bands and those who go to hear them (although I have heard a few mind-boggling exceptions, too).



> Below is a FL wavelet using my preferred EQ with a filter providing; +5.5dB, 401Hz, 4.5Q. The direct sound is boosted that amount in that range. The result is that the SPL dip at the LP is filled 20ms late. My FR EQ is identical.
> 
> View attachment 100194


Pardon my dense question, what is causing the 20 mS delay? Are you using linear-phase filtering? That seems like a lot, although I can think of no particular reason for concern. Just curious.



Audionut11 said:


> On the subject of "SS&I", there are so many variables, is it really any wonder why no one has attempted significant research?


Sadly, I can only agree with you. Like art, I know it when I see it - as Leonard said so well, "It is simply an attempt to find the placement that gives the overall best impression of creating a sound space in which performers are playing music." But getting there with a given set of speakers in a given room is very much trial and error, with certain trends to be followed from experience.

I would be tickled pink if there was even a clear-cut set of acoustical measurements that could tell you when you were "there" or close to it. I have attempted this with FR and phase measurements and have so far been disappointed. A setup with good left/right FR and phase matching can have unclear, imprecise imaging, and when sharp imaging is achieved, FR and phase matching can look way off comparatively.:huh:

Adding in delayed reflection info and ratio of direct-to-reflected sound might help, but the latter is not easily measurable. It all gets nightmarish pretty fast.

As AJ has inferred, a good set of definitions might be a good starting place.


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## jtalden (Mar 12, 2009)

AudiocRaver said:


> ...what is causing the 20 mS delay? Are you using linear-phase filtering? That seems like a lot, although I can think of no particular reason for concern.


This measurement is with IIR PEQ filters using my DCX units. It also includes an FIR phase correction filter designed in rePhase to just remove the direct sound phase rotation; no impact to SPL. The FIR filter has no impact on sound quality that I can hear. It is only there as it helps cleanup the Phase/GD/SR charts. The FIR filter is only active on Stereo Music as it is being implemented using a Foobar2000 music server.

Yes, the 20ms delay for SPL fill seem large to me also, but I haven't heard any ill effects; only a significant improvement in tonality. The cause appears to be a reflection null causing the initial hole in the response at 0ms. I haven't been able to identify the source of that reflection. That is followed by 3 other nulls near the same freq that prevent earlier SPL fill-in. My back wall is 9' from the LP so a reflection from there would arrive about 16ms later. Possibly that is the primary source of the fill-in? Possibly it is more a combination of several late arriving reflections. I really am really challenged to attribute cause to this type of acoustic issue so these are just guesses.


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## ajinfla (May 10, 2009)

jtalden said:


> I am use to hearing those 2 bullets as basic rote from what seems like most all speaker manufacturers. I am not sure why they stress those points so hard with all the evidence that full range EQ can be very helpful in many cases. Harmon developed and sells full range EQ devices (I think) so that makes such firm statements puzzling.


Toole is of course not a manufacturer, so his statements are based merely his own research, while Harman is a manufacturer and free to sell what they think consumers may want. I don't recall him saying full range EQ can't make speakers with poor on/off axis, etc. sound better. If he did then I would have to disagree.



jtalden said:


> The response above maybe 800Hz is fine when the speakers are EQed flat so using direct sound speaker output as flat there is no issue for me assuming some additional EQ roll-off can be applied if needed to meet the LP steady-state house curve. My inclination is though that the target LP response is more important than a flat speaker output in the midrange.


So your speakers are axially flat nearfield above 800hz, but not below? Are they passive or active/DSP? Do you have measurements?



jtalden said:


> My issue is in the midrange 300 to 800Hz. The most notable issue in that area is that both the FL and FR LP responses have a significant sag around 350-500Hz which is a room effect and not the result of floor or ceiling reflection or any other reflection point I have been able to identify.


I have yet to see a room where monopole speakers (99.9% of market) don't show effects well above Schroeder, as can be clearly seen in Tooles measurements as well.
Have you tried others speakers, or better yet, speakers with different polar response that yours, in the same position?



jtalden said:


> Possibly the opponents of full range EQ just lump all these situations into a basket labeled 'bad setup' and discount them? Probably not, but I wish I understood the real situation in that regard.


Not sure who these "opponents" are, but Tooles data certainly indicates that full ranged EQ _shouldn't_ be needed in the majority of rooms with well designed speakers, but that some EQ, perhaps staring as high as 500-800hz, where room modal effects are strongest, will inevitably be beneficial.
That is not the same as saying that some full range EQ can't make things sound better, given that a lot of speakers on the market won't fit Tooles "well designed" category.

cheers,


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## jtalden (Mar 12, 2009)

ajinfla said:


> Toole is of course not a manufacturer, so his statements are based merely his own research, while Harman is a manufacturer and free to sell what they think consumers may want. I don't recall him saying full range EQ can't make speakers with poor on/off axis, etc. sound better. If he did then I would have to disagree.


Yes, I understand and agree with this comment and the impact of it. In Harmon's case it makes the understanding of what is done to boost sales and what is real engineering conviction difficult to decide. In Toole's case I am sure it all makes sense within the scope he covers. My only issues why it doesn't follow for me? Usually things we expect to be true bear out in listening sessions whether or not they are real. In this case the clear preference is counter to the expectation.



> So your speakers are axially flat nearfield above 800hz, but not below? Are they passive or active/DSP? Do you have measurements?


My comparison is between near field axially flat speaker output from 300-20kHz Vs adding the indicated filter that fills a dip around 400Hz that otherwise occurs when measuring at the LP. These are DIY SEAS H1456/H1212 per the 'Equipment List' under my name. DCX2496 provides XO, delay and EQ as needed. The 16L Box is 2nd order/sealed, Qb=~0.5 the poly fiber fill is, if anything, possibly a little over filled from typical. So, there is not much that can go wrong with the MR response from 100-2k range. The speaker is EQ corrected for baffle step, the overall rising response of that driver and for a small resonance peak around 800Hz similar to the response shown in the SEAS driver spec sheet. I have all sorts of measurements and can show some that support this assertion and some that don't. Indoor measurements are somewhat very dependent on window setting and positioning trying to prove it is flat 100-500 is problematic. so we better not go there. I don't have outdoor measurement, but the preponderance of my work suggest the near-field response of the speaker is basically flat with the base EQ until I add this 400Hz filter and one or 2 more below 300Hz to address other modes below the Schroeder.



> I have yet to see a room where monopole speakers (99.9% of market) don't show effects well above Schroeder, as can be clearly seen in Tooles measurements as well.


Room effects? Yes, mine have serious room effects that appear in the midrange up to 600Hz. The question is, it better to EQ those even though it is above the cited upper end of the Schroeder transition frequency or not. My experience is that it is clearly demonstrable that it is better to EQ out my dip even that happens with 20ms delayed. 



> Have you tried others speakers, or better yet, speakers with different polar response that yours, in the same position?


No, I haven't changed speakers. I have nice reasonably uniform horizontal dispersion as shown below. I have close phase tracking through the XO so the central lobe is stable. The vertical dispersion is as expected for a 7" MW and 1" dome; fairly narrow and asymmetric (not shown). It's unavoidable with this configuration.



> Not sure who these "opponents" are, but Tooles data certainly indicates that full ranged EQ _shouldn't_ be needed in the majority of rooms with well designed speakers, but that some EQ, perhaps staring as high as 500-800hz, where room modal effects are strongest, will inevitably be beneficial.
> That is not the same as saying that some full range EQ can't make things sound better, given that a lot of speakers on the market won't fit Tooles "well designed" category.


If it is recognized that in some cases EQ departing from flat axial speaker output may provide some benefit as high as 300-600Hz then that accommodates my situation. It may be that simple. 

Possibly Toole's guideline is intended to provide a very good reliable result that is acceptable for all practical applications and I am just fussing over the last bit of improvement possible beyond that? At least that is one possibility.

It's not like the sound is poor without the filter it is just noticeably better on some material with it. I am very pleased with most all aspects of my current setup. It measures well and has very good SS&I. My interest is as a hobbyist who wants to learn and experiment to develop better understanding and thus drag out the last bit of sound quality that this setup can muster - just for fun. Since I have no source of comparison to other well calibrated systems or to experienced listeners, there is no telling how my setup really sizes-up by comparison. If you or Wayne want to stop by and critique the sound quality, please do. Unfortunately that is probably not going to appear high on your to-do list however. 

Thanks to all for all the comments. Every perspective helps me better understand this. 

30" Unnormalized Horizontal Dispersion 0-90°:


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## AudiocRaver (Jun 6, 2012)

Not sure if this is exactly the statement being referred to:

"Equalization cannot change loudspeaker directivity; the remedy is a better loudspeaker."(p516)

Granted it does not say directly that EQ can/will not sound better, but it seems to be implied pretty strongly.


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## AudiocRaver (Jun 6, 2012)

Jtalden: I penciled you in on my "next time I'm in Michigan" list.


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## jtalden (Mar 12, 2009)

Great! Any time.


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## ajinfla (May 10, 2009)

jtalden said:


> Yes, I understand and agree with this comment and the impact of it. In Harmon's case it makes the understanding of what is done to boost sales and what is real engineering conviction difficult to decide. In Toole's case I am sure it all makes sense within the scope he covers. My only issues why it doesn't follow for me? Usually things we expect to be true bear out in listening sessions whether or not they are real. In this case the clear preference is counter to the expectation.


Regarding Harmans products, I believe on their most sophisticated stereo integrated, there was an option for EQ only<500hz iirc, or the option to EQ full range.
I'm still a bit confused by your case. Aren't you saying no EQ is used/required above 800hz?



jtalden said:


> My comparison is between near field axially flat speaker output from 300-20kHz Vs adding the indicated filter that fills a dip around 400Hz that otherwise occurs when measuring at the LP. These are DIY SEAS H1456/H1212 per the 'Equipment List' under my name. DCX2496 provides XO, delay and EQ as needed. The 16L Box is 2nd order/sealed, Qb=~0.5 the poly fiber fill is, if anything, possibly a little over filled from typical. So, there is not much that can go wrong with the MR response from 100-2k range. The speaker is EQ corrected for baffle step, the overall rising response of that driver and for a small resonance peak around 800Hz similar to the response shown in the SEAS driver spec sheet. I have all sorts of measurements and can show some that support this assertion and some that don't. Indoor measurements are somewhat very dependent on window setting and positioning trying to prove it is flat 100-500 is problematic. so we better not go there. I don't have outdoor measurement, but the preponderance of my work suggest the near-field response of the speaker is basically flat with the base EQ until I add this 400Hz filter and one or 2 more below 300Hz to address other modes below the Schroeder.


Yes, I saw your speakers were DIY and figured you would have some form of diffraction loss filtering (how much was added is unclear). Yes, best measured free space, but regardless, it seems you've accounted for that. So obviously more of a speaker/room modal issue.
One of the main reasons I got in the business. A 6.5" midbass is going to be largely omnidirectional to around 800hz, I assume your baffle isn't much wider than 8 or so inch, so you will get a lot of front wall reflection behind the speaker, combined of course, with all other directions as it radiated 3D, so its never quite that simple. Solution there by my way of thinking, is cardioid radiation, something quite doable with DSP. Then EQ if needed. "Fix" the source first.



jtalden said:


> Room effects? Yes, mine have serious room effects that appear in the midrange up to 600Hz. The question is, it better to EQ those even though it is above the cited upper end of the Schroeder transition frequency or not. My experience is that it is clearly demonstrable that it is better to EQ out my dip even that happens with 20ms delayed.


It's always source/room effects. Not separable. Put a cardioid or dipole where a monopole was, same room, very different result at the LP. Can't be viewed independent of one another.
Yes, the upper range recommended by the paper may need revisiting and I have always contended with Olive and Geddes et al, that EQ alone is not enough. That the radiation characteristics of the source can go beyond what EQ can address. Then make so called passive/active "treatments" a final step, if needed. Clearly you are hearing audible benefit from EQing higher than recommended.




jtalden said:


> No, I haven't changed speakers. I have nice reasonably uniform horizontal dispersion as shown below. I have close phase tracking through the XO so the central lobe is stable. The vertical dispersion is as expected for a 7" MW and 1" dome; fairly narrow and asymmetric (not shown). It's unavoidable with this configuration.


Yes, that is very good response. Perhaps some diffraction effects (not sure of your baffle edge shaping), but very good overall. I imagine a lowish XO. By "different", I meant to see if the 300-600hz dip was consistent.



jtalden said:


> If it is recognized that in some cases EQ departing from flat axial speaker output may provide some benefit as high as 300-600Hz then that accommodates my situation. It may be that simple.
> 
> Possibly Toole's guideline is intended to provide a very good reliable result that is acceptable for all practical applications and I am just fussing over the last bit of improvement possible beyond that? At least that is one possibility.
> 
> It's not like the sound is poor without the filter it is just noticeably better on some material with it. I am very pleased with most all aspects of my current setup. It measures well and has very good SS&I. My interest is as a hobbyist who wants to learn and experiment to develop better understanding and thus drag out the last bit of sound quality that this setup can muster - just for fun. Since I have no source of comparison to other well calibrated systems or to experienced listeners, there is no telling how my setup really sizes-up by comparison. If you or Wayne want to stop by and critique the sound quality, please do. Unfortunately that is probably not going to appear high on your to-do list however.


Nothing to disagree with there and if I'm ever up that way, thanks for the invite. Closest I usually get is Axpona CHI.

cheers,


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## jtalden (Mar 12, 2009)

ajinfla said:


> …
> I'm still a bit confused by your case. Aren't you saying no EQ is used/required above 800hz?


Sorry for the confusion. It is probably due to my way of thinking of the overall EQ situation. I was trying to differentiate between the 'base EQ' and the 'room EQ' portions of my total EQ settings. I'm calling 'base EQ' the filters that are needed to create a flat near-field speaker response. This would be a part of a speaker design that is intended to be sold commercially. It may include compensation for driver response, baffle step and possibly even diffraction effects. The 'room EQ' portion are the filters needed to achieve the desired house curve at the LP. The point was that above 800Hz the filters needed to create a flat speaker response work reasonably well to also achieve the preferred house curve at the LP. Only possibly a some minor roll-off adjustment would be needed for my LP distance. I am agreeing with the paper that having a smooth direct response of the speaker would work fine above 800Hz in my case. 

It was my preference for a filter at 400 Hzthat I was confused about. I, perhaps mistakenly, understood that it would be better not to use that 'room filter' as it is above the modal range.

Some charts may help the understanding. Below is; 'base EQ' for the FL and FR speakers, LP measurement that include the total EQ filters (The 4 shown above and 3 lower ones including the 400Hz filter), 16" measurement with the 'base EQ' (The 4 filters shown). While my total EQ was actually determined at the LP. The measurement at 16" shows that the direct response above 800Hz is relatively flat hence the observation that there is good EQ agreement above 800Hz for these 2 methods in this case. 

Other info relative to your comments:
As you noted, I have tried to keep the XO on the low side to help keep a smoother horizontal dispersion handoff between drivers. The XO approximates an acoustical LR-24 at about 2.2kHz. The front wall is 20 feet behind the speakers so no early reflections there. There are the diffraction effects of the box design and possibly that is at least partially why the higher frequency filters are needed in the base EQ to get a flat direct response. I also attached a measurement file of the 3 front speakers as the LP in case other charts of the overall setup are of interest.

























View attachment LP DLNA-2-3.mdat


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## ajinfla (May 10, 2009)

Thanks and sorry for late reply, got busy with some orders. Looks good.
I think we are in agreement that no or minimal EQ should be needed >800hz and I'm not quite sure if we disagree with Toole, as his own data show issues to 500+ Hz in most rooms, so maybe the "room" to "speaker" transition region is well above 200-300hz, possibly as high as 800hz.
20' from front wall? Lucky you.

cheers,

AJ


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## Raimonds (Jan 8, 2016)

The discussion with Dr. Toole should be interesting for readers of this thread:
http://www.hometheatershack.com/for...n-speaker-correction-discussion-dr-toole.html

BR,
Raimonds


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## jtalden (Mar 12, 2009)

Hi Raimonds,
Thanks for posting that.
I have read Dr. Toole's popular book, his recent paper and seen your comments. As you point out, there is little in specific and practical guidelines for studio/home EQ setup. I find it impossible to understand Dr. Toole's research and the citations well enough draw any confident conclusions of my own on how to proceed with EQ. I am looking forward to more detail coming now that both Dr. Toole and David Smith mentioned that something is in the works. Possibly that will be more helpful. My background in product development and application engineering includes some time on an SAE standards committee. There is lots of 'corporate interest' lobbying in that type of process that impedes development of clear standards. No company wants to see their products/practices fall into a disadvantageous market position. It seems to me the music creation industry is all over the place in terms of studio EQ practices. Hopefully the charts I've seen showing gross variability are dated and things have improved. Possibly this new work will push it along. I am not too confident however as the market forces are strong and entrenched.

I am not familiar with your products and practices and I found it difficult to follow your thoughts on how EQ is best done.

> Sound intensity in a window of some size at the LP?
> Localized Power response in a window of some size at the LP via either 'moving mic method' (MMM) or individual mic positions?
> Should there be a defined house curve for a defined setup or are there too many parameters to make that practical?
> I understood that you advise linear phase response at the LP through the full range. Correct? Some hobbyists indicate linear phase in bass range is not as important and others do not hear any improvement. Also I am understanding that linear phase at the LP would be in reference to the direct sound and not in trying to chase the phase rotations due to room influences (reflections and modes). 
> Do you agree that a single measurement at the LP position is adequate for bass range EQ?
> Do you agree that in most situations the EQ result above maybe 800Hz will be reasonably similar whether the measurements are done via quasi-anechoic at say 1m Vs the LP if an MMM method is used given that there may be appropriate HF roll-off/absorption due to distance?

If my situation is typical, EQ of the bass and HF range practices seem relatively clear compared to the 300-800Hz midrange. Asymmetric room setup and limited acoustic treatments as I have make the EQ of room effects in that range difficult to address. I would agree that it is impossible for EQ to correct the issues, but find that it can help mitigate the severity of them. A professional studio is better able to address the source of the issues through room design and acoustic treatments. I have self-imposed constraints in that area and instead just want a clearer understanding of a process or guidelines to mitigate the damage.

I am not expecting a detailed response to any of this long post, but If you would care to cite a reference to your thoughts on any of these areas, or provide thoughts on any of this here, I would appreciate that. I am mostly just trying to understand how best to deal with the midrange EQ in a nonideal room situation. I like my current midrange EQ setup far better than avoiding EQ in that range. Many experienced hobbyest have advised that any EQ there to address room effects is not advised. I am more inclined to suggest to other hobbyists that they can improve the sound quality via EQ in this range if reasonable methods are used.


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## Talley (Dec 8, 2010)

My uncle has told me that FR is hugely not important... as long as your within a +/- 3 or 5db then your good. 

He does praise proper toe of the speakers.... position within the room... and exactly symmetrical layout and having the speakers elevation, plumb and level exact to to an accuracy of .05°. He said this is vital for pinpoint sound-stage. 

I've listened and his SSI is amazing even though there are a few faults in the FR (particularly the highs falloff too fast imho).


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## jtalden (Mar 12, 2009)

Thanks Talley,
I take that to mean that the anechoic axial response of the speaker should be flat and room effects should not be addressed. Recently, a smooth off-axis response is also often stated as an important factor. This apparently holds up so long as the room is symmetrical and the setup is ideal for speaker, listening positions and appropriate acoustical treatments. I have seen that often stated before and it is rational to me that very good results could be expected. Most, Including Dr. Toole seem to agree that the bass range still benefits from EQ and I assume your uncle does also. But... Does that mean high end studios do not ever EQ above the Schroeder frequency to achieve improved results? Is 1/3 octave RTA, DRC, Audyssey, YPAO, Dirac, Acourate, et.al., all marketing schemes with no real value? I really don't know what EQ practices are common there, but suspect some EQ is applied. If not, then does this change in the case of non ideal setups as mine? Possibly EQ is more valuable in that case. I would think that it might be even more effective there.

I was mostly fishing for more practical guidance relating to what best practices are. From my experience it seem very beneficial to EQ the midrange and to shape the HF. I am a hobbyist having only experience with my room setup, so I am interested as to how my methods compare to more professional ones.


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## Talley (Dec 8, 2010)

jtalden said:


> Thanks Talley,
> I take that to mean that the anechoic axial response of the speaker should be flat and room effects should not be addressed. Recently, a smooth off-axis response is also often stated as an important factor. This apparently holds up so long as the room is symmetrical and the setup is ideal for speaker, listening positions and appropriate acoustical treatments. I have seen that often stated before and it is rational to me that very good results could be expected. Most, Including Dr. Toole seem to agree that the bass range still benefits from EQ and I assume your uncle does also. But... Does that mean high end studios do not ever EQ above the Schroeder frequency to achieve improved results? Is 1/3 octave RTA, DRC, Audyssey, YPAO, Dirac, Acourate, et.al., all marketing schemes with no real value? I really don't know what EQ practices are common there, but suspect some EQ is applied. If not, then does this change in the case of non ideal setups as mine? Possibly EQ is more valuable in that case. I would think that it might be even more effective there.
> 
> I was mostly fishing for more practical guidance relating to what best practices are. From my experience it seem very beneficial to EQ the midrange and to shape the HF. I am a hobbyist having only experience with my room setup, so I am interested as to how my methods compare to more professional ones.


I see value in EQing... but my uncle is a die hard. His system is pure analog. source, pre, amp... speaker done. I think he would value from it but nothing I can do to change his 45yrs of hi-fi.


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## bearr48 (Jan 26, 2014)

Thanks, guys, for this really interesting discussion (& you especially Wayne, for getting it going)! My knowledge is not sophisticated enough to understand all that has been said, but I do get (and appreciate) some of it. Thanks again.

Jack Brent


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## Raimonds (Jan 8, 2016)

jtalden said:


> Hi Raimonds,
> Thanks for posting that.
> I have read Dr. Toole's popular book, his recent paper and seen your comments. As you point out, there is little in specific and practical guidelines for studio/home EQ setup. I find it impossible to understand Dr. Toole's research and the citations well enough draw any confident conclusions of my own on how to proceed with EQ. I am looking forward to more detail coming now that both Dr. Toole and David Smith mentioned that something is in the works. Possibly that will be more helpful. My background in product development and application engineering includes some time on an SAE standards committee. There is lots of 'corporate interest' lobbying in that type of process that impedes development of clear standards. No company wants to see their products/practices fall into a disadvantageous market position. It seems to me the music creation industry is all over the place in terms of studio EQ practices. Hopefully the charts I've seen showing gross variability are dated and things have improved. Possibly this new work will push it along. I am not too confident however as the market forces are strong and entrenched.
> 
> ...


Thank you for your valued opinion and questions!
I will try to answer.

*) As I am pointing to focus on loudspeaker performance I do not use such term as Listening Point. Even very early users of my works were referencing lack of any sweet spot and any connection to some listening point when the correction was introduced. Of course, there are some special cases when loudspeakers have very narrow directivity. Special measures are taking place in such cases.
*) The loudspeaker’s Sound Power response (for far field applications) is base.
*) The MMM is a trial to reinvent some part of this work, published in 2005 
http://www.google.com/patents/US8121302

*) I did not see any benefit of use of Linear Phase filters in any application. I am using Minimum Phase correction filters from very start in 2002. Because of 1) no latency 2) the minimum phase problems of loudspeaker are corrected ideally- as from amplitude as from phase prospective. The beauty of that you can see in LF correction when large GD caused by main resonance of loudspeaker, is removed.

*) I do not understand any attempts to do some correction from one point measurement (or few points) that are connected to some LP. Because of fact that any trial to fill up some dip on FR (caused by room modes or interference – non minimum phase behavior) is requesting narrow resonant peak on equalizer’s FR. That two „processes” are not with opposite sign – they do not compensate each other as it is with basic assumption of the use of correction that - predistortions, which are introduced by equalizer, will be compensated (neutralized) by distortions of system that we are truing to equalize.

If we are looking for exception quality in LF we should turn to near field setup with appropriate EQ. The TDA EQ is for that.

Our, human, listening perception is build such way that it extracts the „color” of sound source even in case of far field. We will percept any predistortions as distortions of sound source if such predistortions are not closely connected to real distortions of source – loudspeaker. This is true especially up from midrange.




> ... as long as your within a +/- 3 or 5db then your good.


This is true for listening for enjoyment and when „problems” are wide band.

The job of recording/mix engineer is requesting decision making within accuracy of 1...2 dB and the monitor system with respective accuracy is requested.

If you are willing to catch (listen for) nuances of different „handwriting style” of each engineer/producer/label, you should have a loudspeaker system with appropriate accuracy.



> ...the anechoic axial response of the speaker should be flat...


It is impossible to find true axes even for loudspeakers with smooth and wide directivity...


But, if little bit touch the room, the most degradating factor of room are its windows.
Nothing can be more problematic than a real large window next to yours speakers.

BR,
Raimonds


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## GrizzlyAK (Dec 5, 2015)

Very interesting discussion. No disrespect intended... I am new to HTS, coming here primarily for REW information, with a background and interest in film sound post-production. 

I found the OPs comments about Toole's paper quite subjective given that I've just spent the last 3-4 months studying in depth Dr. Toole's book "Sound Reproduction: Loudspeakers and Rooms", as well as his various talks, presentations, and papers on the subject (including the subject paper), and I don't consider any of the OPs statements regarding Toole's work to be a fair assessment. 

If one has read (and understood) his book, then it would be clear that the OPs assessment of Toole's focus (or lack thereof) is incorrect. I find Toole's research completely relevant to the discussion taking place here, and more than relevant. Granted, I am not familiar with the term "Soundstage & Imaging" or SS&I, nor is Google apparently, finding nothing of relevancy in a search. From what I can gather in these discussions, though, it appears to be a more subjective psychoacoustic approach to setting up your sound, which is perfectly appropriate in many situations, but is more than adequately addressed in both Toole's book AND the subject paper. I found much in Toole's book directly related to Home Theaters and their setup.

However, much of Toole's research does address cinemas simply because cinema is the only industry in sound who has a 'closed' calibration standard (SMPTE 202, the X-curve). However, as he rightly points out, and Ioan Allen confirms, in developing the X-curve 'standard', no real science was done - it was a subjective match that produced the X-curve used by theaters the world over and in every major dub stage where predictable sound from production to presentation is desired. The findings presented in this paper even point out that the standard is often 'subjectively' altered to overcome some of the standard's shortcomings in sound reproduction in theaters.

Contrary to the OPs statements, Toole, in his early days at Harman, pioneered the measurement of off-axis sound from loudspeakers, and notified the industry of their importance in the overall sound-field, in both early and late reflections and in the reverberant sound-field (which really doesn't exist in small rooms). His research goes so much deeper than just placing some unknown speakers in an unknown room, and EQ'ing until it sounds good (the subjective approach, which is not sufficient for critical listening and standardization - more is needed). It's importance is clear when a true understanding of how a fully specified speaker (with complete anechoic data) will react in a particular room, and in being able to predict what a room curve will look like based upon that data before measurements are ever made. This all has very much to do with off-axis sounds.

Finally, it must be understood that the subject paper addresses a _specific _problem: challenging the standard assumption that a steady-state amplitude response measurement is the best calibration choice, and the one used in cinemas and mixing rooms everywhere. This is only a glimpse of what is known and what has been studied. If you are interested in reading more about how off-axis sound affects what you hear, whether for movies or 'SS&I' (and whether or not good off-axis performance is really that important in certain situations), I would certainly recommend more than a cursory read of Toole's book. I'm a physicist and it took me two full reads, quite a bit of reflection, and several conversations with the author, to fully grasp the content. It's definitely NOT light reading, but I found it quite illuminating.

Cheers,
Shane


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## witwald (Jun 22, 2010)

AudiocRaver said:


> Ears are fallible. Imaginations are powerful. Any individually-derived conclusion must be scrutinized relative to proven facts.


It seems that the concept of Sound Stage & Imaging (SS&I) would be a prime candidate to fall within the confines of the assessment process that was described above. Has anyone attempted to do that? If so, what were their results?

It would seem that the audible results of SS&I are heavily influenced by the orientation of the loudspeakers relative to the listening position, and the vagaries of each individual listening room. Until you have a standardized room, it's going to be difficult to assess this parameter, even for high-end listeners. It may be prudent to keep in mind the underlying effects of imagination on the listening experience, or rather, the ability of our brain to create a "stereo image".



> [That the] hoped-for "calibration methodology that could be applied throughout the audio industry" (abstract) appears to disregard a critical slice of the high-end listener pie.


It would seem more likely that the opposite is true. The high-end listener is potentially less likely to seek out a standardization of their listening space to obtain consistently reproducible sound quality from one listening room to another. Doing so might serve to reduce the effect of imagination on the SS&I listening experience.


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