# does anyone know?



## nineballg (Jan 19, 2008)

i've got all the first reflections covered with panels but i'm running 7.1 system and i was wondering about the reflections for the surround speakers. dont they need panels for their reflections?


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## eugovector (Sep 4, 2006)

nineballg said:


> i've got all the first reflections covered with panels but i'm running 7.1 system and i was wondering about the reflections for the surround speakers. dont they need panels for their reflections?


 It doesn't hurt, all though, the goal is diffused, non-directional sound from those speakers, so you want a little reflection, especially with di-poles. There's probably a much more scientific way to do it, but I use the 7.1 clicks on AVIA at a good level to see how much reflection you're getting. With my absorption for my fronts on the front, back, and side walls, I didn't address the surrounds directly, just let the existing panels do it.

Since only about 10% (fake number pulled out of my end) of the movie sound comes out of the surround channels, I wouldn't lose any sleep over it.

One caveat, it probably would be good, if your surrounds are within 2-3 feet of a side wall, to treat that wall next to them with a small panel. It should help with speaker boundary interference response (SBIR).


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## Ethan Winer (Jul 21, 2006)

nineballg said:


> i was wondering about the reflections for the surround speakers.


My philosophy is to absorb first reflections for _all_ speakers in a system. The problem with early reflections is they create a skewed frequency response known as _comb filtering_ - a series of many peaks and deep nulls. If you don't want a badly skewed response for your mains, I can't see why you'd want that for the surrounds either. :nerd:

--Ethan


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## nineballg (Jan 19, 2008)

thanks guys


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## avaserfi (Jul 5, 2007)

Ethan Winer said:


> My philosophy is to absorb first reflections for _all_ speakers in a system. The problem with early reflections is they create a skewed frequency response known as _comb filtering_ - a series of many peaks and deep nulls. If you don't want a badly skewed response for your mains, I can't see why you'd want that for the surrounds either. :nerd:
> 
> --Ethan


Is this your methodology for all forms of treatment? What about a two channel system in which the off axis response of the speaker is near identical to that of the axial response?

It has been shown through perceptual research that these first reflections actually increase enjoyment. Would you recommend treating anyways, if so why?


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## Ethan Winer (Jul 21, 2006)

avaserfi said:


> Is this your methodology for all forms of treatment?


Yes.



> What about a two channel system in which the off axis response of the speaker is near identical to that of the axial response?


Same advice. If you think about it, when the off-axis response is the same as on-axis, that makes the resultant comb filtering even more damaging because all frequencies are reinforced and canceled maximally. Assuming perfect reflectivity of course.



> It has been shown through perceptual research that these first reflections actually increase enjoyment.


_My_ research shows exactly the opposite. :devil:

It might be that in a very large room - and I'm talking 20 feet wide or wider - that side-wall reflections are less damaging than in a more typical size room. But generally speaking, small-room reflections are always best avoided IMO. Especially if the reflecting surfaces are closer than ten feet to your ears. BTW, this includes the rear wall behind you too.

--Ethan


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## nineballg (Jan 19, 2008)

i'm not sure. too technical for me, i'll let the pro ethan explain it


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## Kal Rubinson (Aug 3, 2006)

avaserfi said:


> It has been shown through perceptual research that these first reflections actually increase enjoyment.


Enjoyment is highly subjective and multivariate. Can you offer a link to such research?


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## avaserfi (Jul 5, 2007)

Ethan Winer said:


> Same advice. If you think about it, when the off-axis response is the same as on-axis, that makes the resultant comb filtering even more damaging because all frequencies are reinforced and canceled maximally. Assuming perfect reflectivity of course.


You are right there would be comb filtering created as a side effect of this methodology, but in Floyd Toole's research it was shown that despite this comb filtering the slightly delayed reflections were still found to be more enjoyable than use of an unreflective surface. All relevant articles are cited below.



Ethan Winer said:


> _My_ research shows exactly the opposite. :devil:


What kind of research is this? How was it done? Do you by any chance have the publication listing so I can read it?



Ethan Winer said:


> It might be that in a very large room - and I'm talking 20 feet wide or wider - that side-wall reflections are less damaging than in a more typical size room. But generally speaking, small-room reflections are always best avoided IMO. Especially if the reflecting surfaces are closer than ten feet to your ears. BTW, this includes the rear wall behind you too.


While a large room would be beneficial in reduction of comb filtering as previously mentioned the preference still lay with a reverberant surface in place.




Kal Rubinson said:


> Enjoyment is highly subjective and multivariate. Can you offer a link to such research?


You would actually be surprised how many facets of speaker design have been solidified as ideal and non-ideal. While certain tendencies lay with preference credible research has shown that most do not. Some of these are obvious such a smooth on axis frequency response and the ability to dynamically produce lower frequencies. Some others include a lack of all audible resonance, off-axis response similar, if not matching, the axial response, a gradual roll off of the treble to match how the human ear works (this one in part lies with preference as some people prefer a larger roll off than others). 

There are various papers on these subjects. Floyd Toole has many regarding relating measurements to listener preference as well as room interaction. 

Some notable articles of his include (I will not be able to link these as they aren't posted online your local library would be your best bet):

_Listening Tests-Turning Opinion into Fact_ JAES Volume 30 Issue 6 pp. 431-445; June 1982

_Subjective Measurements of Loudspeaker Sound Quality and Listener Performance_ JAES Volume 33 Issue 1/2 pp. 2-32; February 1985

_Loudspeaker Measurements and Their Relationship to Listener Preferences: Part 1 _JAES Volume 34 Issue 4 pp. 227-235; April 1986

_Loudspeaker Measurements and Their Relationship to Listener Preferences: Part 2_ JAES Volume 34 Issue 5 pp. 323-348; May 1986
_
The Modification of Timbre by Resonances: Perception and Measurement_ JAES Volume 36 Issue 3 pp. 122-142; March 1988
_
The Detection of Reflections in Typical Rooms_ JAES Volume 37 Issue 7/8 pp. 539-553; July 1989
_
Loudspeakers and Rooms for Sound Reproduction—A Scientific Review_ JAES Volume 54 Issue 6 pp. 451-476; June 2006

Well it looks like I have listed all of his articles. I guess this is because simply put he is the leading researcher involved with perception in relation to loud speakers. Also, if you look up Ian Paisley's research you will see that through thousands of blinded trials with thousands participants, that wider and smoother frequency responses were highly preferred in a controlled environment.


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## Ethan Winer (Jul 21, 2006)

avaserfi said:


> You are right there would be comb filtering created as a side effect of this methodology


Exactly, and I can't imagine how anyone could consider such a terribly skewed response to be a desirable artifact. Worse, the comb filtering response changes dramatically over tiny distances, like an inch or less. This is why untreated early reflections are so damaging to imaging. You move your head just a little and everything changes. Versus how imaging _should_ be where everything is locked into place, and comes from the same location no matter where you are in the room.



> in Floyd Toole's research it was shown that despite this comb filtering the slightly delayed reflections were still found to be more enjoyable than use of an unreflective surface. All relevant articles are cited below.


I've read Floyd's position and I respectfully disagree. I don't know of one other expert who agrees that early reflections in a typical domestic size room are desirable. And by expert I include every professional designer of recording studios I know of.



> Do you by any chance have the publication listing so I can read it?


Here ya go:

http://www.realtraps.com/rfz.htm

Figures 1 and 2 tell all. This is in addition to many listening tests.

Do me a favor? Please describe your own listening room and its acoustic treatment. If you can post a photo of the front of the room too all the better. Thanks.

--Ethan


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## avaserfi (Jul 5, 2007)

Ethan Winer said:


> Exactly, and I can't imagine how anyone could consider such a terribly skewed response to be a desirable artifact. Worse, the comb filtering response changes dramatically over tiny distances, like an inch or less. This is why untreated early reflections are so damaging to imaging. You move your head just a little and everything changes. Versus how imaging _should_ be where everything is locked into place, and comes from the same location no matter where you are in the room.


Perhaps I have not made myself completely clear. It is well known that proper distances between each loudspeaker as well as the listener is needed for proper speaker placement in any room. Although, it doesn't seem that a room the size you have previously mentioned would be required. I am speaking of a system with proper placement and full treatments under the methodology that first reflections should be encouraged with proper off-axis response.

I fully understand the idea of comb filtering and the artifacts that occur from doing so, but the relevant credible research shows that *in spite* of this artifacts the slightly delayed reflections are desirable for stereophonic listening. 

Also, I am very well aware of the factors effecting imaging: Loudspeaker room interaction, symmetry of response with respect phase with response to listener position and lastly treble response. All these variables can be controlled with proper treatment and equalization even with first reflections left "live."

This brings up another question with an omnipolar speaker would you treat the first rear to the speaker reflection? This is another situation that would cause even more comb filtering and has been proven through credible research to increase stereophonic listening pleasure.



Ethan Winer said:


> I've read Floyd's position and I respectfully disagree. I don't know of one other expert who agrees that early reflections in a typical domestic size room are desirable. And by expert I include every professional designer of recording studios I know of.


I have talked to multiple professionals [same meaning as yours] who have differing opinions on the subject. For strictly two channel listening in a completely dedicated room with proper treatments I have gathered that many of them follow Toole's research. In fact, one specifically told me the gut reaction to treat first reflections is an outdated practice from treating recording studios. 

It seems logical that application would change treatment needs after all.



Ethan Winer said:


> Here ya go:
> 
> http://www.realtraps.com/rfz.htm
> 
> ...


I am aware of your website, but there is a difference between that and Toole's work. No offense is intended by this statement, but Toole's research methodology was peer reviewed before being published in the JAES while your studies were not. Furthermore, there is no discussion of the listening tests and the methodology of your research on the site you supplied as far as I am aware.

My current room is not dedicated and laid out in an asymmetric way in which treatment of the first reflections is necessary. I am referring to an ideal circumstance far from my own. I do however have a friend with an extremely high quality omnipolar 2-channel system with axial and off-axis response near identical to each other. He personally conducted blinded studies with both musicians as well as other individuals with his results mimicking Toole's. Personally, I have gone into a Hi-Fi shop and played with such treatments in a subjective manner to the same effect as well.


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## Ethan Winer (Jul 21, 2006)

avaserfi said:


> I fully understand the idea of comb filtering and the artifacts that occur from doing so, but the relevant credible research shows


Look guy, if you like the comb filtered sound of untreated early reflections, and the resultant affect on imaging, more power to you. But tossing out the names and credentials of _other people_ means nothing to me. For every pro you cite who says untreated reflections are good I can point to ten others who say that's wrong. So what? It seems to me the best approach is for people to hear for themselves and draw their own conclusions. I've done this enough times to know how damaging those reflections are, and I intend to continue advising people to use absorption there.

--Ethan


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## avaserfi (Jul 5, 2007)

Ethan Winer said:


> Look guy, if you like the comb filtered sound of untreated early reflections, and the resultant affect on imaging, more power to you. But tossing out the names and credentials of _other people_ means nothing to me. For every pro you cite who says untreated reflections are good I can point to ten others who say that's wrong. So what? It seems to me the best approach is for people to hear for themselves and draw their own conclusions. I've done this enough times to know how damaging those reflections are, and I intend to continue advising people to use absorption there.
> 
> --Ethan


I simply was trying to have an open discussion about a specific methodology within the world of acoustics. I have now realized this is not possible at least in terms of this thread.

On another note I am not sure I understand how citing _relevant_ research is inappropriate. In fact it is my understanding properly conducted peer reviewed research should be used and applied otherwise what is the point?

Have a good day. 

-Andrew


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## bpape (Sep 14, 2006)

Early reflections from the main 3 speakers are definitely undesirable. In the rear, it's not AS critical since you want a non-localizable 'soundstage'. In multi-channel, we always treat the front and rear differently. We always kill the front wall completely but never kill the rear wall completely. 

This is not to say that there is not comb-filtering, there is. It's not to say that it doesn't have an impact on frequency response, it does. What it is, is a tradeoff. One can have no comb filtering for the rear by creating an RFZ for all of those too - but at the expense of the diffuse soundstage that is desirable.

It's a lesser of 2 evils and most won't lose the soundfield envelopment and be able to pinpoint their surrounds to save a bit of frequency response abberations. If you stop and think about it, diffusion can cause some of the same issues due to out of time arrivals and some cancellations in the wells but the effect it gives is still more desirable than the flat wall. Same kind of trade off.

And no, before someone jumps on me about diffusion and specular reflections being the same thing, they're not. They can just yield some of the same kinds of effects. It's all in what you're trying to accomplish. If I can let part of the room work for me instead of deadening even more of the mid and high frequencies, I'll do that. If we were to plot every reflection point for all 7 speakers for all seats in a room, almost every single surface in the room would be 90+ % covered with absorbtion. Then you've shot your balanced target decay time curve.

Just my 2 cents.

Bryan


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## WmAx (Jan 26, 2008)

Ethan Winer said:


> But tossing out the names and credentials of _other people_ means nothing to me. For every pro you cite who says untreated reflections are good I can point to ten others who say that's wrong.


In regards to your general statement regarding universal absorption of the 1st horizontal reflection points......

The difference between avaserfi's citations and your claims, though, is that it appears that yours are *not* from sources that have performed careful, scientifically valid experiments to come to their conclusions.

You have every right to believe what you want. But the _credible_ evidence available does not appear to support you.

-Chris


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## Ethan Winer (Jul 21, 2006)

WmAx said:


> The difference between avaserfi's citations and your claims, though, is that it appears that yours are *not* from sources that have performed careful, scientifically valid experiments to come to their conclusions.


Most of the research I'm aware of that concludes early reflections are desirable focused on _speech intelligibility_, not music. So right off the bat the research is invalid in the context of this thread.

I repeat this again - every professional designer of recording studios I know of agrees that first reflections are damaging and should be absorbed.

--Ethan


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## Ethan Winer (Jul 21, 2006)

More thoughts on this:

There are educated listeners and uneducated listeners. Often I hear from what I consider uneducated listeners that they prefer the sound of their room rather than a treated room. To me this is related to the conventional wisdom that a 2-channel room should be more live sounding than a home theater. I happen to disagree with that - most movies have music, and that music should sound as the mix engineers intended. If absorption in a home theater improves imaging, then it does the same for a 2-channel setup. So I guess you could say a well-treated room can be an acquired taste. In my experience small room ambience is always bad ambience. Versus a room large enough to have true reverb. But then we're outside the realm of home listening environments.

I work with many professional recording and mastering engineers, and I consider them to be educated listeners. These people listen to music for a living, and if they can't hear clearly how the music really sounds, without being influenced by the sound of their own room, they can't do their job. From my perspective, the listener at home should aim to hear the same quality as the engineer heard when mixing. And that means not leaving early reflections untreated.

Of course, there's no accounting for taste, and it's not my job to tell someone what they should or should not prefer and enjoy. All I can do is address the science of audio, and from that perspective it's clear (to me, anyway) that comb filtering due to early refections is best avoided.

--Ethan


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## bpape (Sep 14, 2006)

Ethan.

Not to get into a tiff, but some real questions.

- How many of those guys mix multi-channel?

- How many of the mixing rooms have 90% of their wall surface covered in broadband absorbtion (which is what it would take to catch all the reflections from all of the speakers to all of the seats in a home theater)?

And sorry, but I'll disagree that a 2 channel room and a multi-channel room should be treated the same. In multi-channel, I have independent speakers to reproduce the diffuerent aural cues of the space. In a 2 channel system, you don't and you HAVE to count on the room to help you a little bit.

Have you ever listened to a good 2 channel recording outside? If it's anything that has 'space' to it like an orchestral piece or a choral piece recorded in a hall or church, it'll sound awful. It sounds thin and uninvolving. Now, if you listen to the 'in the box' over produced, electronic stuff that HAS no 'space' to it, then it'll sound about the same.

Guess that's up to 4 cents now :rofl2:

Bryan


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## WmAx (Jan 26, 2008)

Ethan Winer said:


> Most of the research I'm aware of that concludes early reflections are desirable focused on _speech intelligibility_, not music. So right off the bat the research is invalid in the context of this thread.
> 
> I repeat this again - every professional designer of recording studios I know of agrees that first reflections are damaging and should be absorbed.
> 
> --Ethan


The work by Ando, and analysis by Toole, all contained in Loudspeakers and Rooms for Sound Reproduction -- A Scientific Review, goes as far as examining both speech and classical music, and 1st horizontal reflections with the appropriate time delay and amplitude enhanced perceived sound quality to subjects. In Toole's summary, it is determined that reflections need _augmentation_ by additional channels in order to be at a high enough level to be fully satisfactory to subjects. It should also be noted, that in the paper titled Modification of Timbre by Resonances, it is found that an increased reflective fields _reveals more timbre information_ within a recording. This is also one suspected factor.

-Chris


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## WmAx (Jan 26, 2008)

Ethan Winer said:


> Often I hear from what I consider uneducated listeners that they prefer the sound of their room rather than a treated room. To me this is related to the conventional wisdom that a 2-channel room should be more live sounding than a home theater. I happen to disagree with that


I am not sure if you intend this to be directed towards me. But just in case it is, it should be noted that I have never suggested an untreated room is ideal for anything. I am a strong proponent of proper treatment plans. Plans that must take into account the specific speaker radiation patterns in any particular circumstance along with the known reflective angles and time windows preferable as found by valid perceptual research.



> - most movies have music, and that music should sound as the mix engineers intended.


Actually, I would disagree strongly where 2 channel is concerened. Some control rooms are almost as an anechoic chamber, when you consider the level of treatments combined with near field placed speakers. This certainly does not meet the requirements of ideal sound quality for listeners as dictated by credible researchers such as Toole.

I find the same preferences personally, as found in the Toole analysis. For context, I have both an extremely linear, low resonance near field monitor system in a highly acoustically treated environment replicating the type preferred in a traditional studio environment. This is a monitor system with lower resonance and higher linearity as compared to most high end studio monitor speakers. In addition, I have a dedicated listening room with a speaker system featuring near omnipolar dispersion. The omnipolar system is treated according to the perceptual work as dictated by Toole, in both reducing cross channel interference(using unusual large middle room divider absorption units) and by way of reducing random reflection/reverberation in the room, but keeping the horizontal 1st reflection points in tact, and in an angular and time based limits as specified by Toole. The omnipolar system is not as linear, nor quite as low resonance as the near field system - and yet -- the omnipolar system sounds far more realistic subjectively - while the monitor system is a little more 'detailed' analytically - it is far less realistic. Sort of like listening to headphones is the best way I can describe it, when compared to the omnipolar system. It is further interesting that if I place absorbers at the 1st reflection points in the omnipolar system, that realism is devestated. It just sounds like a really good monitor system - not realistic like being at a real classical orchestra performance. I have repeated this for various people(with audio back grounds) and all end up with the same preference in regards to realism effect - which I don't believe is by just chance - since sound quality enhancements are specifically predicted by Toole under this condition.

-Chris


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## eugovector (Sep 4, 2006)

It's hot like AVS in here :bigsmile: Thanks everyone for keeping cool heads. There's a reason why I spend more time here than I do there.

I do appreciate this discussion. I find myself agreeing with Bryan's assessment that reflections have more to add in 2-channel, than multi-channel. I find myself very happy with my multichannel performance, yet wanting to dabble in diffusion on my rear wall in search of a little more spaciousness to my 2 channel music. Those are my answers, most certainly not THE Answers.

Thanks for the lively debate.

Marshall


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## bpape (Sep 14, 2006)

One can actually do both. One of my favorite tricks is to use absorbtion on the rear wall but absorbtion that has a reflective layer on it. This acts to help minimize bass cancellations off the rear wall of the room while preserving a more lively and non-localizable surround stage. Couple this with diffusion on the rear half of the side walls and the effect can be quite staggering.

Bryan


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## Ethan Winer (Jul 21, 2006)

bpape said:


> Not to get into a tiff, but some real questions.


Of course not! We're just discussin' stuff. :whew:



> How many of those guys mix multi-channel?


First, let's not confuse the importance of absorbing first reflections with the issue of 2-channel versus HT sound. My comment that all professional studio designers favor absorbing first reflections is in response to Andrew's claim that first reflections are best untreated. Ironically, Andrew has a thread going on in another forum where he shows how he built absorber panels including for first reflections. :devil:



> How many of the mixing rooms have 90% of their wall surface covered in broadband absorbtion (which is what it would take to catch all the reflections from all of the speakers to all of the seats in a home theater)?


Why would you need to cover 90 percent of a normal size room to catch all early reflections? Using ten feet away on-axis as a guideline, that means only a few more 2x4 foot panels for the surrounds. My living room is treated for all early reflections, and you may recall the time at AVS where I summarized my percentage surface coverage versus the common method of covering the entire front wall plus all other walls up to ear height. I came in at about 2/3 as much surface coverage.



> In a 2 channel system, you don't [have independent speakers to reproduce the diffuerent aural cues of the space] and you HAVE to count on the room to help you a little bit.


I could not disagree more strongly. Just as with HT 5.1 surround, all of the ambience required for 2-channel is already embedded in the recording. Didja ever listen to a great stereo recording on headphones and marvel at how huge and spacious it sounds? This is exactly what you get in a room too when all the reflection points are treated. IMO small room ambience is always bad ambience, and should not be allowed to contaminate a recording. Indeed, for this very reason, allowing a small room to impart its own ambience from nearby surfaces makes the music sound _smaller,_ not larger.



> Have you ever listened to a good 2 channel recording outside?


That's not what I'm talking about either. Again using my living room as an example, the majority of surfaces are reflecting! Only the corners, back wall, and reflection points are treated (plus carpet).



> Guess that's up to 4 cents now :rofl2:


Heh, I just dropped at least a dime if not a quarter. :demon:

--Ethan


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## eugovector (Sep 4, 2006)

Ethan Winer said:


> I could not disagree more strongly. Just as with HT 5.1 surround, all of the ambiance required for 2-channel is already embedded in the recording.
> 
> --Ethan


I think that's, unfortunately, far from the case. In fact, it seems these days that popular music is recorded very dry. There are a few great albums coming out these days with real ambiance, Feist's _The Reminder_, for instance. Most are recorded very dry and need a little help from the room to give them life (blame the techs, or producers, or artists). Of course, those, mostly ignored, ambiance settings aka Fake Reverb built into your 5.1 system could offer them same, though it certainly won't sound as good.


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## avaserfi (Jul 5, 2007)

avaserfi said:


> Is this your methodology for all forms of treatment? What about a two channel system in which the _*off axis response of the speaker is near identical to that of the axial response*_?
> 
> It has been shown through perceptual research that these first reflections actually increase enjoyment. Would you recommend treating anyways, if so why?





Ethan Winer said:


> First, let's not confuse the importance of absorbing first reflections with the issue of 2-channel versus HT sound. My comment that all professional studio designers favor absorbing first reflections is in response to Andrew's claim that first reflections are best untreated. Ironically, Andrew has a thread going on in another forum where he shows how he built absorber panels including for first reflections. :devil:


I have mentioned many times that certain characteristics of the speakers must be of sufficient quality to use this philosophy. The commercial speakers I purchased do not fit this qualification and thus require such treatment. There is a reason I am designing a pair of custom speakers for myself.

I am not arguing all first reflections should be untreated, but in the specific situations previously mentioned it has been shown through credible research that preference lay with untreated first reflections. 

Do you have any credible research to back up your claims? If so I would gladly read it and comment on this research as well.


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## Ethan Winer (Jul 21, 2006)

WmAx said:


> it is found that an increased reflective fields _reveals more timbre information_ within a recording.


I find this highly suspect. It sounds like the subjects confused the skewed response from comb filtering with increased harmonic content. At least I assume that's what is meant by "more timbre information" which is a meaningless term. I liken this to boosting the upper mids with an EQ which has a similar effect. Only in this case the "timbre" boosts are the comb filter peaks from reflections. This is a perfect example of the uneducated listeners I mentioned yesterday. They confuse boosted upper mids with higher clarity and better presence. A professional recording or mastering engineer would never make that mistake, and would spot the characteristic sound of comb filtering immediately and ask "What idiot placed the microphones for this piano track?!" :hissyfit:



> Some control rooms are almost as an anechoic chamber, when you consider the level of treatments combined with near field placed speakers.


Tell me if this looks anechoic:










The control room above was designed by Wes Lachot, a leading proponent of treating all early reflections. Note that in this case those reflections are avoided by angling the walls sufficiently to direct the reflections to the rear of the room, around the mix position. But the ideal is the same, and when a room is not wide enough to allow this Wes chooses absorption.

Now let's move on to designer Fran Manzella, another strong proponent of treating all early reflections:










Click HERE and HERE to see other representative rooms Fran has designed. Note the extensive use of diffusors to avoid making the room seem anechoic, while ensuring that all reflections are taken care of. BTW, if you question any of this you can ask Fran yourself in his forum HERE.

Then there's John Storyk:










This doesn't look anechoic to me. Does it to you? Though in this case John has thick curtains at the side wall reflection points rather than traditional panels.

Here's Marshall Long Acoustics, again using large side angles to do what otherwise requires absorption in small rooms:










Again, I'd hardly call any of these modern commercial control rooms anechoic.



> This certainly does not meet the requirements of ideal sound quality for listeners as dictated by credible researchers such as Toole.


This is why I object to characterizing the guys one agrees with as credible, while dismissing those we disagree with. It just avoids discussing the issues and relies instead on "[Famous Guy] says so therefore it must be true." And this applies to me and my "famous guy" photos above too. But hopefully my words explains the issues well enough to make the point, and not rely only on the logical fallacy _Argument from authority_ in showing these photos.

--Ethan


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## Ethan Winer (Jul 21, 2006)

eugovector said:


> it seems these days that popular music is recorded very dry.


Yes, and that's a stylistic choice made by the producers. Just like too much reverb as often done 30 years ago. But purposely not treating reflections to add more life is no different than buying a reverb effect and patching in to your system. If you wouldn't do that, why would you do the equivalent acoustically? And with a reverb device, at least you'd have a bunch of _high quality_ reverb presets to choose from. :R

--Ethan


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## WmAx (Jan 26, 2008)

Ethan Winer said:


> I could not disagree more strongly. Just as with HT 5.1 surround, all of the ambience required for 2-channel is already embedded in the recording.


You may disagree. But this view point does not match the credible modern perceptual research into the subject.




> Didja ever listen to a great stereo recording on headphones and marvel at how huge and spacious it sounds?


Since when does a stereophonic recording ever sound as if it has a realistic size soundstage on a headphone, unless a special binaural recording is used or DSP software to emulate a binaural soundfield?

Odd implication that frankly, I can't remember ever seeing in the past, even on a snake oil headphone site like head-fi.org. Of course, this does not mean such a claim has been made and I simply missed it....

-Chris


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## WmAx (Jan 26, 2008)

Ethan Winer said:


> I find this highly suspect. It sounds like the subjects confused the skewed response from comb filtering with increased harmonic content. At least I assume that's what is meant by "more timbre information" which is a meaningless term.


If you were familiar with the research on audibility/perception of resonances, perhaps you would not make such baseless accusations such as 'confused subjects' or 'uneducated listeners'. Then again, perhaps you are familiar with the research in question, but simply do not care to give it any weight, in exchange for your own anecdotal evidence.



> This is why I object to characterizing the guys one agrees with as credible, while dismissing those we disagree with. It just avoids discussing the issues and relies instead on "[Famous Guy] says so therefore it must be true." And this applies to me and my "famous guy" photos above too.


My qualifier when picking data has no weight given to 'fame'. I cite the data concluded from careful scientific experimentation. For the most part, within this thread, you cite speculations and anecdotal evidence. This is not equal to, nor can I give it remotely close weight, to the carefully collected data by credible scientists in this field.


-Chris


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## avaserfi (Jul 5, 2007)

Ethan, you keep focusing on the comb filtering created by having a reverberant first reflection point, but perceptual research has shown that our brain and ears in combination are not microphones. In fact the mechanisms involved in this process have actually been shown to be so advanced that we will in a sense fill in the gaps. After all when "listening in the elaborate comb filters called concert halls" [1] it still sounds great. I believe Blauert says it best: "Clearly, then, the auditory system possesses the ability, in binaural hearing, to disregard certain linear distortions of the ear input signal in forming the timbre of the auditory event" [2].

[1] Loudspeakers and Rooms for Sound Reproduction - A Scientific Review. Toole, Floyd E. J. Audio Eng. Soc., Vol. 54, No. 6, 2006 June.

[2] Spatial Hearing - The Psychophysics of Human Sound Localization, Blauert, J. rev. ed. MIT Press, Cambridge, MA, 1997.

As far as reflections increasing the audibility of resonance WmAx is correct. This claim is clearly supported by The Modification of Timbre by Resonances: Perception and Measurement. Toole, Floyde E. J. Audio Eng. Soc. Vol. 36 Issue 3 pp. 122-142; March 1988. This increased audibility of resonance clearly makes more timbre information available after all do instruments do to create sound? This is analogous to Bryan's example of listening to music outside. Without room reinforcement of sound waves much of the timberal information will be lost.

Again, I will ask do you have _any_ *credible** data to back up your claims? This would greatly aid in the discussion.

*Credible research refers to a peer reviewed paper conducted using strict controls and published in a legitimate source.


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## Ethan Winer (Jul 21, 2006)

Guys, I'm not going to argue this further. I've made all the points I possibly can, and I have explained in great detail why untamed early reflections make music sound lousy in a typical size room. If you guys prefer that sound, more power to you.

--Ethan


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## darrellh44 (Aug 18, 2007)

WmAx said:


> In addition, I have a dedicated listening room with a speaker system featuring near omnipolar dispersion. The omnipolar system is treated according to the perceptual work as dictated by Toole, in both reducing cross channel interference(using unusual large middle room divider absorption units) and by way of reducing random reflection/reverberation in the room, but keeping the horizontal 1st reflection points in tact, and in an angular and time based limits as specified by Toole. The omnipolar system is not as linear, nor quite as low resonance as the near field system - and yet -- the omnipolar system sounds far more realistic subjectively - while the monitor system is a little more 'detailed' analytically - it is far less realistic.
> 
> -Chris


Hi Chris,

Based on this excerpt from your earlier post and what I've read on other forums and the Linkwitz Lab webpage, it seems the key factor in determining whether early reflections are desirable is the main speaker's dispersion pattern over frequency.  Specifically if the mains' dispersion pattern becomes increasingly more focused with increasing frequencies (as is typical with all monopole speakers), then early reflection absorption is needed. If on the otherhand the dispersion pattern is uniform over frequency (Linkwitz says a dipole's figure-eight pattern is best), then early reflections are desirable. 

Does this fit your understanding of early reflection absorption applicability? Do you think this might be why there is such a disparity in anecdotal experiences? Do you believe that an optimum two-channel setup with uniform dispersion and proper room treatments (no early reflection absorption) will always be more realistic than multi-channel approaches, now and in the future? 

Thanks,
Darrell


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## avaserfi (Jul 5, 2007)

darrellh44 said:


> Based on this excerpt from your earlier post and what I've read on other forums and the Linkwitz Lab webpage, it seems the key factor in determining whether early reflections are desirable is the main speaker's dispersion pattern over frequency. Specifically if the mains' dispersion pattern becomes increasingly more focused with increasing frequencies (as is typical with all monopole speakers), then early reflection absorption is needed. If on the otherhand the dispersion pattern is uniform over frequency (Linkwitz says a dipole's figure-eight pattern is best), then early reflections are desirable.


The original question I posed to Ethan was in regard to monopolar speakers with off-axis and on-axis responses that are nearly identical (meaning the entire frequency response). In this case it has been shown that untreated/reflective first reflections are perceived as more enjoyable than a treated first reflection.

In the case of a dipole/omnipolar speaker rear first reflections that vectors to the listener have also been shown to be desirable along side the typical first reflection as well. Other reflections in this situation such as cross wall reflection will be detrimental and should be tamed appropriately.

The essential reading on this topic can be found in 
Loudspeakers and Rooms for Sound Reproduction—A Scientific Review JAES Volume 54 Issue 6 pp. 451-476; June 2006



darrellh44 said:


> Does this fit your understanding of early reflection absorption applicability? Do you think this might be why there is such a disparity in anecdotal experiences? Do you believe that an optimum two-channel setup with uniform dispersion and proper room treatments (no early reflection absorption) will always be more realistic than multi-channel approaches, now and in the future?


The disparity coming from anecdotal experiences is likely due to the fact that few loudspeakers have on/off-axis responses that are similar enough in magnitude to appropriately implement this ideal treatment plan.

In regards to the belief that this is the proper methodology of treatment this belief is based on credible perceptual research that was done with strict controls for bias. In the future more research might be done that leads to different styles of treatments, but as of now this seems to be the best methodology if the proper loudspeaker is used according to the available credible research.


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