Absorption only on front wall?

[subframe]

No offense taken, I agree that getting decent performance is going to be challenging at best! Thanks for the reference.

I actually had not considered in-wall speakers but that's an intriguing idea for sure.

 

[FrankW]

Hi, in the third edition of Sound Reproduction, Toole references Ando, Y. (1977). “Subjective Preference in Relation to Objective Parameters of Music
Sound Fields with a Single Echo,” J. Acoust. Soc. Am., 62, pp. 1436–1441, writing "Adding absorption to the front wall, behind the loudspeakers, reportedly improved image localization and reduced coloration" and "Memo for Listening room recommendations: add sound absorbing material to front wall."

Thanks, just what I was looking for!

 

[krabapple]

I always say, "Diagnosis before treatment". So it's best if you can measure the room first, and again after treatment to make sure you've made an improvement.

Usually the "real problems" are in the bass range and that requires bass traps. Regular "acoustic panels" do absorb much (if any) bass.

You meant do NOT, I can tell. ;>

 

[krabapple]

My, we do seem to rehash these reflections debates a lot, don't we?

 

[youngho]

No offense taken, I agree that getting decent performance is going to be challenging at best! Thanks for the reference.

I actually had not considered in-wall speakers but that's an intriguing idea for sure.

I was thinking about active speakers like Genelec or Kef that have boundary compensation settings; cardioid dispersion ones like Dutch & Dutch 8C, Kii Three, or Mesanovic CDM65; or possibly home theater surrounds like Perslisten R4S that have been designed specifically for on-wall use (with subwoofer), although your mileage may vary significantly on the success of said implementation (look for measurements whenever possible, but Amir's data shows some seem to perform very badly)

 

[Bjorn]

Hey, finally Frank got a straw to hold on to.
Seriously, when someone doesn't even understand that flutter echo is bad for sound or that speaker dispersion has an effect on specular energy and thus sound quality, it may be best to educate oneself. We're talking very basic psycoacoustic knowledge here and someone are screaming for blind tests for proof!

 

[LTig]

The goal is to end up with a system and room that allows for enjoying music casually - with friends over, during dinner, relaxing in the evening, but which also sounds *good enough* that if something good comes on and I want to focus and really listen, I can do so. Ultimate fidelity is not the goal - I have another dedicated listening room where I can pursue that goal should I wish. Budget is flexible - whatever I do will not be a significant portion of the remodel budget, trust me lol. However, aesthetics do matter - it's our living room and it cost a lot of money to get it done the way we want, so I'm not going to want to stick 4" absorbers or corner traps everywhere willy nilly.

I've attached a diagram of the room. Circled in green are the only available places for treatment other than the front wall. Everything else is either glass or kitchen cabinets. Red circles are where the speakers will go, of course.

Maybe I have cloth ears but looking at the diagram I would start with just a pair of excellent speakers without any room treatment, just room EQ below Schroeder, and a thick rug between speakers and sofa. It looks similar to my living room, with one complete side as windows from floor to 2m height, and the furniture of the kitchen and bookshelves on the other side are enough treatment to get really got sound - that is to my cloth ears.

 

[FrankW]

Hi, in the third edition of Sound Reproduction, Toole references Ando, Y. (1977). “Subjective Preference in Relation to Objective Parameters of Music
Sound Fields with a Single Echo,” J. Acoust. Soc. Am., 62, pp. 1436–1441, writing "Adding absorption to the front wall, behind the loudspeakers, reportedly improved image localization and reduced coloration" and "Memo for Listening room recommendations: add sound absorbing material to front wall."

Hi Youngho, thanks again for remembering Sound Repro so well as to direct me. But you are mistaken, I read the Ando paper and it has nothing to do with that quote. That is actually from Kishinaga paper On the Room Acoustic Design of Listening Rooms (1997). I read this paper also, have you read/investigated either of those 2? The news is not good for the treatment sellers. First and foremost, the opening line says it all, the "listening room" is actually a "monitor" room for audio professionals, NOT home listeners/living rooms. It gets worse from there, although in defense, it was 1979. All tested were "audio professionals". The test methods and measurements used would be highly questionable today, use of "room curves" for direct/reflected spectra, layout for speakers (pointed straight forward, no toe in etc), etc. But focusing on the main point, front wall "treatments", there was weak, but some evidence that the audio pros preferred the treatments. *However, this particular condition was only tested when ALL walls were also absorptive:
In order to examine the effect of the specifications of rear walls behind the speakers on the subjective impression,
listening test was conducted by changing the specifications of the rear wall behind the speakers in six steps from
completely reflective material to completely absorptive, with the side walls and the rear wall behind the listener in absorptive conditions.
I regret to inform you the lifeline you threw Bjorn turned out to be a anchor/sinker. That paper has zero relevance to living rooms/home listeners in good mental health.
I was so puzzled by Tooles Memo that you cited, that I reached out to him as I did before (became an AES member during pandemic to pore through as much perceptual research as I can). He responded and is in 100% agreement with me. Sorry. I have asked him for any future editions of his books, to revise that Memo, which is a bit misleading if read without context. Quite frankly (pardon the pun), there is zero reason for any "living" room listener to absorb the front wall, unless of course, as you noted, literally on or very near the wall placement of speakers (which OP didn't say in post I quoted originally). The OP might certainly consider this, but "normal" p[placement of floor/stand speakers at bit out from wall (or like Toole himself), needs no such "treatments".
If anyone has double blind listening tests to suggest otherwise, please cite.

 

[FrankW]

Hey, finally Frank got a straw to hold on to.
Seriously, when someone doesn't even understand that flutter echo is bad for sound or that speaker dispersion has an effect on specular energy and thus sound quality, it may be best to educate oneself. We're talking very basic psycoacoustic knowledge here and someone are screaming for blind tests for proof!

That you sell treatments but can't cite a single listening test is quite telling.

 

[FrankW]

Maybe I have cloth ears but looking at the diagram I would start with just a pair of excellent speakers without any room treatment, just room EQ below Schroeder,

Agreed and it's probably your eyes that are clothy, in that you don't need to see "treatments" to enjoy great sound.

 

[Dal1as]

Hi Youngho, thanks again for remembering Sound Repro so well as to direct me. But you are mistaken, I read the Ando paper and it has nothing to do with that quote. That is actually from Kishinaga paper On the Room Acoustic Design of Listening Rooms (1997). I read this paper also, have you read/investigated either of those 2? The news is not good for the treatment sellers. First and foremost, the opening line says it all, the "listening room" is actually a "monitor" room for audio professionals, NOT home listeners/living rooms. It gets worse from there, although in defense, it was 1979. All tested were "audio professionals". The test methods and measurements used would be highly questionable today, use of "room curves" for direct/reflected spectra, layout for speakers (pointed straight forward, no toe in etc), etc. But focusing on the main point, front wall "treatments", there was weak, but some evidence that the audio pros preferred the treatments. *However, this particular condition was only tested when ALL walls were also absorptive:
In order to examine the effect of the specifications of rear walls behind the speakers on the subjective impression,
listening test was conducted by changing the specifications of the rear wall behind the speakers in six steps from
completely reflective material to completely absorptive, with the side walls and the rear wall behind the listener in absorptive conditions.
I regret to inform you the lifeline you threw Bjorn turned out to be a anchor/sinker. That paper has zero relevance to living rooms/home listeners in good mental health.
I was so puzzled by Tooles Memo that you cited, that I reached out to him as I did before (became an AES member during pandemic to pore through as much perceptual research as I can). He responded and is in 100% agreement with me. Sorry. I have asked him for any future editions of his books, to revise that Memo, which is a bit misleading if read without context. Quite frankly (pardon the pun), there is zero reason for any "living" room listener to absorb the front wall, unless of course, as you noted, literally on or very near the wall placement of speakers (which OP didn't say in post I quoted originally). The OP might certainly consider this, but "normal" p[placement of floor/stand speakers at bit out from wall (or like Toole himself), needs no such "treatments".
If anyone has double blind listening tests to suggest otherwise, please cite.

I don't think you are seeing the whole picture or possibly do not know how room modes work in what is considered a small room.

Anyone who has invested time doing thorough bass management knows that sbir can really mess things up.

Absorption panels behind a speaker are definately needed to tame it. Usually at least 5 inches thick.

I was in a dolby lab where they had a 5 inch thick 3 to 6 foot panel behind every speaker.

There were like 60 or so speakers in there. They didn't do all that for fun.

Acting like room treatment in a small room is snake oil or not needed is ridiculous.

 

[FrankW]

Anyone who has invested time doing thorough bass management knows that sbir can really mess things up.

I have no doubt it messes up your eyes/head. Any double blind listening tests to cite from your invested time? No? Ok.

 

[youngho]

Hi Youngho, thanks again for remembering Sound Repro so well as to direct me. But you are mistaken, I read the Ando paper and it has nothing to do with that quote. That is actually from Kishinaga paper On the Room Acoustic Design of Listening Rooms (1997). I read this paper also, have you read/investigated either of those 2? The news is not good for the treatment sellers. First and foremost, the opening line says it all, the "listening room" is actually a "monitor" room for audio professionals, NOT home listeners/living rooms. It gets worse from there, although in defense, it was 1979. All tested were "audio professionals". The test methods and measurements used would be highly questionable today, use of "room curves" for direct/reflected spectra, layout for speakers (pointed straight forward, no toe in etc), etc. But focusing on the main point, front wall "treatments", there was weak, but some evidence that the audio pros preferred the treatments. *However, this particular condition was only tested when ALL walls were also absorptive:
In order to examine the effect of the specifications of rear walls behind the speakers on the subjective impression,
listening test was conducted by changing the specifications of the rear wall behind the speakers in six steps from
completely reflective material to completely absorptive, with the side walls and the rear wall behind the listener in absorptive conditions.
I regret to inform you the lifeline you threw Bjorn turned out to be a anchor/sinker. That paper has zero relevance to living rooms/home listeners in good mental health.
I was so puzzled by Tooles Memo that you cited, that I reached out to him as I did before (became an AES member during pandemic to pore through as much perceptual research as I can). He responded and is in 100% agreement with me. Sorry. I have asked him for any future editions of his books, to revise that Memo, which is a bit misleading if read without context. Quite frankly (pardon the pun), there is zero reason for any "living" room listener to absorb the front wall, unless of course, as you noted, literally on or very near the wall placement of speakers (which OP didn't say in post I quoted originally). The OP might certainly consider this, but "normal" p[placement of floor/stand speakers at bit out from wall (or like Toole himself), needs no such "treatments".
If anyone has double blind listening tests to suggest otherwise, please cite.

Sorry, Toole referenced the Ando and then the Kishinaga paper in the same paragraph, and I hastily assumed the former was the relevant. one. I'm not an AES member, and I didn't go to the original papers, but I do generally try to provide relevant quotes that can be easily referenced (I don't have the third edition handy, but I believe that he made the same recommendation there). Still, perhaps it's interesting that some of Toole's own recommendations have not always seemed to reflect rigorous double-blind testing. Toole has written about the possible need for absorption in listening rooms (for example, https://gearspace.com/board/showpost.php?p=15187387&postcount=61), although much of this may be achieved through home furnishings, also there is page 335 of the second edition of Sound Reproduction ("The absorbers on the front and rear walls avoid reflections within the angular ranges that contribute little to the perception of envelopment"), though the front wall portion might be relevant for the rear surrounds for home theater. I do agree with another poster about SBIR in general, though it's not clearly relevant in the OP's situation, as further distance from the front wall results in lower frequency for the first null, but that wouldn't be well-addressed by 2" PET, while close proximity tends to tilt up the frequency response below ~1 kHz or so (page 191 of second edition of Sound Reproduction), but 2" PET would have decreasing absorption at lower frequencies

 

[FrankW]

I do agree with another poster about SBIR in general

In terms of visible/measurability, or audibility?

 

[youngho]

In terms of visible/measurability, or audibility?

Hi, it sounds like you're asking me about my opinion, instead of double blind testing to back up my statement regarding SBIR in general, which is not necessarily specific to the boundary behind the speakers. It is my understanding that the audibility of dips may depend on the frequency (I'm going to speculate without supporting evidence that a few hundred to several thousand Hz may represent a relatively more critical range of the frequency spectrum), depth/magnitude (shallower less likely to be audible), width/Q (narrower less likely to be audible), and the acoustics of the listening environment (more reflective meaning less audible in terms of the dips). The potential audibility of dips has been discussed, although I don't know about double blind testing, in a variety of situations or circumstances ranging from the seat dip effect in concert halls, floor bounce, and interaural crosstalk intrinsic to stereo, aka the Shirley curve (this last one is not an example of SBIR but rather the audibility of a visible/measurable dip, with both measurability and audibility dependent on the acoustics of the listening environment). Also, I'm not qualified to offer meaningful commentary on the audible effects of proximity of loudspeakers to the wall behind them (has been discussed on ASR and elsewhere before), but I have seen certain so-called experts like Sigfried Linkwitz and Kevin Voecks advocate for relative free-field placement, like >3' from the nearest boundary, for loudspeakers not designed for soffit or in-wall placement. The SBIR effects relative to the front wall can be ameloriated by crossing over to boundary-proximal low bass sources.

In any case, I hope I provided useful information to the original poster @subframe. I don't think I really have anything else to contribute to this discussion at this point.

 

[LTig]

Agreed and it's probably your eyes that are clothy, in that you don't need to see "treatments" to enjoy great sound.

Certainly - when I listen intensely I close my eyes and focus on sound.

 

[FrankW]

Hi, it sounds like you're asking me about my opinion, instead of double blind testing to back up my statement regarding SBIR in general

No, I was asking since your memory of Sound Repro is much better than mine! I had forgot that Toole wall Memo/Kishinaga thing until you reminded me, which I thanked you for. Was wondering the same for SBIR. I've seen it innumerable times on audio forums, but as usual, never any audibility correlation. Don't recall in Sound Repro either.
I understand the effect of scary looking graphs and fancy sciencey sounding words on certain types, but from a personal standpoint, I'm only interested in audibility as it applies to my ears and my F36s etc.
Thanks again, I think you've answered my SBIR audibility evidence question. I of course searched AES/Google etc first, but you never know...