I got a few acoustic panels - Where should I put them?

[amirm]

2. I'm not advocating that side wall reflections should be "taken away" or that side wall reflections are undesirable, haven't I made that clear? I'm saying that without more information you cannot "safely say" that some reduction in side wall reflections is not beneficial. We know the room is relatively small, has parallel surfaces and is certain to have some issues but we do not know the output of the speakers, the wall materials or the interaction between the two. I agree that in most cases there are places other than the side reflection points which should be given treatment priority but we cannot "safely say" anything without having any idea of the variables at play. Case in point ...

No, we can say that. Research has been conducted in many conditions and results have been the same. Even when off-axis sound is not very good, addition of side-reflections has been positive.

The data holds even when we include the excluded group: the professionals who record/mix music. In the peer reviewed Journal of AES paper, The Practical Effects of Lateral Energy in Critical Listening Environments, this very thing was tested in controlled environment to determine preference for diffusion, absorption or doing nothing (reflections). Here was the outcome:

We see the preference is highest for doing nothing (reflections. Here is how that broke down:

So the highest percentage preference is for reflection. Again, this is the group that was tested:

A group that we normally give a pass to that might like absorption of side reflections.

This has been my area of study for almost a decade. When I post such conclusions it it is not idle chatter to just be dismissed with "it depends." The advice to leave side reflection alone is very safe and should be the assumed strategy unless proven otherwise.

3. The majority of people probably do like ice cream but you cannot safely say/instruct someone to eat ice cream without being more sure of the variables: Is the person you're giving the ice cream to a diabetic, are they lactose intolerant, does the ice cream contain any nut products, do they have a dental/nerve problem, etc. Your "safely say" could in fact kill someone! You cannot always take specific circumstances/conditions, scientific experiments and apply the results absolutely to all circumstances/conditions.

So if someone asks if one USB cable sounds better than the other, do you ask if they are deaf in one ear? Or do you just give advice that they would sound the same?

Instead of analogies of this sort which are not helpful at all, if you want to sway what is being recommended, you need to provide research to back it. And be specific. Doing otherwise just spreads doubt for the sake of spreading doubt. OP asked a question, one that a lot of audiophiles want to know. I have provided sum total of what modern acoustic science knows about the topic.

 

[gregorio]

[1] So the highest percentage preference is for reflection. ... The advice to leave side reflection alone is very safe and should be the assumed strategy unless proven otherwise.
[1a] ... if you want to sway what is being recommended, you need to provide research to back it.
[3] I have provided sum total of what modern acoustic science knows about the topic.

1. Huh? The evidence YOU have quoted CLEARLY demonstrates the opposite of what you are claiming! 15 of the subjects preferred acoustic treatment while only 11 preferred to "leave side reflection alone". How does this research support your claim that your advice to leave side wall reflections alone is "very safe" and "should be the assumed strategy"?
1a. Doesn't the same apply to you? Surely you don't mean "to provide research" which you misinterpret/misrepresent in order "to back it [up]"? Additionally, you stated "Research has been conducted in many conditions and results have been the same." - Can you provide the research of those "many conditions" and the research where those "conditions" were the same as the OP's?

2. No you haven't, you have provided your personal interpretation of what you personally know about modern acoustic science! Furthermore, there are areas of music/audio where science advances our knowledge/understanding but does not necessarily provide an accurate or unambiguous understanding. Sometimes, just reading the literature/research results in an inaccurate understanding, due to not sufficiently appreciating the context, of not knowing the conditions under which that literature/research is only partly applicable or even completely inapplicable. Often (and particularly with room acoustics), practical professional experience is required in order to better appreciate that context. For example, several years before room acoustics became your "area of study", I was responsible for teaching several sessions to degree students on Sabine's formula. At the end of the sessions it was necessary to inform the students that in practise Sabine's formula is relatively useless (in practice it's often so imprecise that it's of very limited or no use). Nevertheless, Sabine significantly advanced the science of acoustics, to the point of being widely regarded as the father of modern acoustics.

G

 

[amirm]

1. Huh? The evidence YOU have quoted CLEARLY demonstrates the opposite of what you are claiming! 15 of the subjects preferred acoustic treatment while only 11 preferred to "leave side reflection alone". How does this research support your claim that your advice to leave side wall reflections alone is "very safe" and "should be the assumed strategy"?

You know, it is very difficult to have a technical discussion with you. Not only do you not read the research papers I have put forward, you are not paying attention to summeries I am providing either. Here it is the part of the post you missed:

The data holds even when we include the excluded group: the professionals who record/mix music....A group that we normally give a pass to that might like absorption of side reflections.

So to make sure you don't misunderstand again, I said at the outset that vast majority of listeners in controlled tests prefer side reflections. But that there is a group that tends to want absorption and that is people who use their room for work, i.e. recording/mix engineers. The paper I referenced last digs into this bucket of people who are taught to like absorption as a whole. And it discovers that even this group has the largest preference for doing nothing for side-walls. So the *excluded* group is even smaller than once thought.

I quoted and highlighted the test subjects for this very reason:

Yet you still missed it.

So once again, we are testing the exception here, not the rule. The rule, i.e. what ordinary listeners including audiophiles want by far seems to be to leave side reflections alone.

 

[amirm]

1a. Doesn't the same apply to you? Surely you don't mean "to provide research" which you misinterpret/misrepresent in order "to back it [up]"?

No it doesn't apply to me because I put full links to research papers for you or anyone else to read. If there is a misunderstanding, then all you have to do is quote the paper to show how. You have not done so. None of your posts, or bigshot before you, have any references whatsoever to scientific research. None.

Additionally, you stated "Research has been conducted in many conditions and results have been the same." - Can you provide the research of those "many conditions" and the research where those "conditions" were the same as the OP's?

Your question is non-sequitur because you have not read or understood the nature of research. The research aims to understand how we hear. If I told you listening tests tell us we can't hear 30 Khz, will you demand that I show that in every person's listening room? I assume not. Same is true here.

The conditions here that have been tested has been across many listeners and researchers. Yet the conclusions have been the same.

Let's take a concert hall which is radically different space than home. Here, the same phenomenon holds true. See Journal of ASA paper, Lateral reflections are favorable in concert halls due to binaural loudness

Indeed in a concert hall past the front few rows ("Critical Distance or Dc"), just about everything you hear are reflections!

So the notion that reflections are bad in general should be dialed out of our minds. Side reflections in the specific generate more sense of spaciousness and wider source than the point of speaker. This is just goodness. And hence the reason it is shown in research to be true.

Now, you want to point out what in OP's situation is unique that makes our human behavior, I am all ears. Until then, it is an attempt to create doubt with nary any back up.

 

[amirm]

2. No you haven't, you have provided your personal interpretation of what you personally know about modern acoustic science!

Sorry, no. I provide you exact words from research that 100% agrees with my summaries. Despite repeating this accusation you have yet to demonstrate the validity of it.

Furthermore, there are areas of music/audio where science advances our knowledge/understanding but does not necessarily provide an accurate or unambiguous understanding. Sometimes, just reading the literature/research results in an inaccurate understanding, due to not sufficiently appreciating the context, of not knowing the conditions under which that literature/research is only partly applicable or even completely inapplicable. Often (and particularly with room acoustics), practical professional experience is required in order to better appreciate that context. For example, several years before room acoustics became your "area of study", I was responsible for teaching several sessions to degree students on Sabine's formula. At the end of the sessions it was necessary to inform the students that in practise Sabine's formula is relatively useless (in practice it's often so imprecise that it's of very limited or no use). Nevertheless, Sabine significantly advanced the science of acoustics, to the point of being widely regarded as the father of modern acoustics.

Sabine? His work is nearly 100 years old! You are not even in the right century there. Yes he is considered the "father of modern acoustics" but that is compared to nothing but vudu before it. Modern acoustics in my vernacular is one that fully encompasses psychoacoustics.

Let me show you a summary of history of acoustics through decades, as so well put by Dr. Peter D'Antonio (founder of the most well-known acoustic product manufacturer, RPG). I will skp to 1970s to save time:

This is where the advice to "kill reflections" came from and to this day, improperly advised as we see in this thread and countless others in other forums. No controlled testing backed any of these rules yet studio after studio copied this NE style room.

The next decade becomes super important because it is the first time we start to conduct real, scientific experiments, using controlled testing to better understand our hearing system in an acoustic environment:

Notice mention of Dr. Toole whose work I have been quoting and is considered one of the fathers of this research:

I will skip 1990s as that was a boring decade. Here is 2000s:

Again, Dr. Toole's name pops up, showing that reflections are misunderstood and that they can be quite beneficial.

So yeah, you do need to advance to modern acoustic research where psychoacoustics is an inseparable part of it.

This knowledge does not come quickly. You will need to embrace it fully and dig deep to understand it.

The argument "we don't know" doesn't fly here either unless you demonstrate that you have read the proper research. Without doing so, of course you don't know.

 

[bigshot]

So how is the original poster doing? I'm more interested in him. I lived in a one bedroom apartment for many years and had to find a way to incorporate good sound into it. My best technique was to pay my rent on time so when the neighbors complained, the landlord would ignore them.

Hey Gregorio, you're the one he's gunning for now. I called his bluff and he backed off me.

 

[gregorio]

You know, it is very difficult to have a technical discussion with you. Not only do you not read the research papers I have put forward ...

Not as difficult as it is to have a technical discussion with you because you either do not read or you misinterpret/misrepresent the research papers you yourself put forward and even though I've pointed this out to you, you just blindly continue to misrepresent what you've put forward! Once again ...

[1] Sorry, no. I provide you exact words from research that 100% agrees with my summaries.
[2] The paper I referenced last digs into this bucket of people who are taught to like absorption as a whole. And it discovers that even this group has the largest preference for doing nothing for side-walls

1. Sorry no. You provided the exact words from research that 100% disagrees with your summaries!
2. You're clearly misrepresenting what that paper discovered! What is discovered is in fact the OPPOSITE of what you're stating/summarising: "that even this group has the largest preference for" acoustically treating the side walls, NOT for "doing nothing"! 8 preferred diffusion treatment, 7 preferred absorption treatment and 11 preferred no treatment ("doing nothing"). 8 + 7 = 15 and 15 is greater than 11, is it not?

If I told you listening tests tell us we can't hear 30 Khz, will you demand that I show that in every person's listening room? I assume not. Same is true here.

Oh, so it's OK for you to use analogies but not anyone else? Maybe if I used an analogy similar to your's, you'd be happy: If I told you that we can't hear 14kHz and backed that up with research which demonstrated that 15 test subjects could hear 14kHz and 11 couldn't, would you believe me? I assume not. Same is true here!!

So the notion that reflections are bad in general should be dialed out of our minds.

Then why don't you dial it out of your mind then? I have not stated that reflections are "bad in general", in fact I've consistently stated the exact opposite!! Where we appear to disagree is that I assert there is an optimal range for the amount/level of reflections and therefore above that range is bad. Under such circumstances treating those reflections is therefore good, although by "treating" I am obviously not suggesting completely removing all reflections as that would take us below the optimal range and also be "bad".

[1] No controlled testing backed any of these rules yet studio after studio copied this NE style room
[2] I will skip 1990s as that was a boring decade.

1. Depends what you mean by "controlled", obviously it's not possible to do a quick switching double blind test between different control room designs but yes, there was testing, both objective and subjective, I know the BBC did a fair amount for example.
2. No it wasn't, there were a lot of interesting developments in acoustics, including in room design philosophies. CIM for example, which was a sort of variation on the RFZ idea and ESS, which is effectively a sort of inverse LEDE philosophy.
What ALL the different philosophies require, including Ambechoic and the even more recent MyRoom philosophy, is the acoustic treatment of side reflections! So how does any of that support your assertion of leaving the side walls alone?

The argument "we don't know" doesn't fly here either unless you demonstrate that you have read the proper research.

And have you read the "proper research"? Not according to your posts so far! In fact, what is the "proper research"? You do not know what the OP's listening preferences are, you do not know what acoustic issues his room has and you therefore do not know what research is applicable! For example, it would not be uncommon in an untreated room of those dimensions to suffer from a flutter echo between the side walls, do you have the "proper research", research which demonstrates that a flutter echo is preferable to using some absoption to remove it?

G

 

[amirm]

And have you read the "proper research"? Not according to your posts so far! In fact, what is the "proper research"? You do not know what the OP's listening preferences are, you do not know what acoustic issues his room has and you therefore do not know what research is applicable! For example, it would not be uncommon in an untreated room of those dimensions to suffer from a flutter echo between the side walls, do you have the "proper research", research which demonstrates that a flutter echo is preferable to using some absoption to remove it?

Flutter echo? In that room? And what is the fix for flutter echo? Absorbers on both walls or just one? Hint: the latter. Once you get rid of reflection from one side, there is no need to worry about it bouncing from the other.

Also, flutter echo occurs at higher frequencies so a thin absorber is good enough for that. That is unlike side reflection points where you want to have a broadband absorber (read thick) that is effective down to transition frequencies.

1. Depends what you mean by "controlled", obviously it's not possible to do a quick switching double blind test between different control room designs but yes, there was testing, both objective and subjective, I know the BBC did a fair amount for example.
2. No it wasn't, there were a lot of interesting developments in acoustics, including in room design philosophies. CIM for example, which was a sort of variation on the RFZ idea and ESS, which is effectively a sort of inverse LEDE philosophy.
What ALL the different philosophies require, including Ambechoic and the even more recent MyRoom philosophy, is the acoustic treatment of side reflections! So how does any of that support your assertion of leaving the side walls alone?

"Not possible" or "difficult" to perform controlled listening tests is no reason to believe in anecdotal work done without it. Consumers can't do instant AB switches of USB cables. We don't give them a pass to then believe in sonic differences between them. Same here. Lack of controlled testing lead to all that folklore of BBC rooms, RFZ, etc. That, and crappy speakers of the time.

Now, if you had read the research in general and the papers I have presented, you see that a very effective technique has been created to determine the audible effects of various reflections at different levels and angles.

An anechoic chamber is used with multiple speakers. The main one in front represents the direct sound. Other speakers then represent other reflections. Here is a picture from Dr. Olive's paper showing this common set up for two different angles of reflections:

As the text explains, using this setup we can test for many conditions from impact of reflection level to their angle and location. Since the room is anechoic, no sound comes from other directions so we can test just that one specific angle. The outcome is results like this:

Here, the dots on the graphs show the threshold of detection for each reflection in the form of level it needs to be and its delay (distance to listener). In other words, we don't care about such reflections if they fall below the graph. Our hearing just ignores such reflections -- something we intuitively think otherwise. That reflections are all heard as "echos" and therefore must be "bad." Well if you don't even hear them in some circumstances, clearly that assumption is false.

Notice how the angle of the reflection matters here and hence the reason advice is different for side-wall reflections versus others.

Also note the picture of the dotted speakers. That is what reflections do. Pull the main speaker toward that dotted imaginary speaker, providing a widening of the sound image ("ASW") and more feeling of envelopment. This is a desirable effect, and one that is utilized far more in multi-channel sound where we literally have the above setup in our own homes.

Of course, there is a point where reflections have sufficient delay and amplitude as to then be a problem (that is a room that is "too live"). So somewhere between the threshold of hearing them and the bothersome level is where you want to live. Don Davis in one of his old article, quoting Barron et. al. shows this well:

He summarizes thusly in the text:

Alas, he still believed in LEDE concept which simply doesn't stand to scrutiny given modern research.

FYI there are other techniques to perform this research including using gated response in ordinary rooms which I won't get into.

The key thing here is to understand that we are trying to understand how our hearing works in acoustic spaces. This is why it is called psychoacoustics research. Until you dig in and study the field, you will continue to live in a stale world where lay intuition was used instead of real data and understanding of our hearing system.

 

[bigshot]

Call the Geek Squad!

 

[gregorio]

[1] Flutter echo? In that room?
[2] And what is the fix for flutter echo?

1. A room with relatively large parallel side walls reflecting mid/high-mid frequencies, something like painted gypsum board for example. Not uncommon.
2. That would be some sort of acoustic treatment wouldn't it? It wouldn't be; "do nothing"/"leave the side walls alone"!

Now, if you had read the research in general and the papers I have presented, you see that a very effective technique has been created to determine the audible effects of various reflections at different levels and angles.

That's sailing close to the wind of misrepresentation again! I would say more accurately "a very effective technique has been created to determine the audible effects of certain, specific reflections at different levels and angles" - Namely, the principle, initial reflections. This technique effectively suffers from one of the same failings as Sabine's formula, in a real room we don't just have principle, initial reflections, we have secondary, tertiary and more reflections (reflections of reflections), which interact both with the direct sound and with ALL the other reflections, summing and cancelling, raising and lowering the level and duration of the reflections. In practise, in real rooms, this interaction quickly becomes a chaotic system. This technique then is a way of isolating/modelling a small part of what actually occurs in real rooms and then testing that "small part". In practice, testing real rooms subjectively is extremely difficult, as you would know if you had not only read the research but had significant practical experience enabling you to more appropriately interpret that research!

[1] Here, the dots on the graphs show the threshold of detection for each reflection in the form of level it needs to be and its delay (distance to listener). In other words, we don't care about such reflections if they fall below the graph.
[2] Our hearing just ignores such reflections -- something we intuitively think otherwise. That reflections are all heard as "echos" and therefore must be "bad."
[2a] Well if you don't even hear them in some circumstances, clearly that assumption is false.

1. Agreed, in general.
2. Again, agreed. That's hardly the most modern or esoteric acoustics/psycho-acoustics research though, it's nearly 70 years old and the Haas/Precedence Effect is/should be taught to pretty much all audio engineering students.
2a. What have I stated that demonstrates I'm making that assumption?

Of course, there is a point where reflections have sufficient delay and amplitude as to then be a problem (that is a room that is "too live"). So somewhere between the threshold of hearing them and the bothersome level is where you want to live.

Isn't that what I've been saying, that there is an optimal range? In relatively small rooms, such as the OP's, we're always going to get "too live" (in terms of either reflections/reverb which is too loud/long or in terms of the amount and number of reflection interactions causing freq response problems) and so we're always going to need acoustic treatment. But, how much treatment, of what type and where to position it all depends on factors we do not know. We do not know the OP's listening preferences (of what he feels is too much/long reverb) or the specific acoustic problems in his room.

[1] The key thing here is to understand that we are trying to understand how our hearing works in acoustic spaces.
[2] Until you dig in and study the field, you will continue to live in a stale world where lay intuition was used instead of real data and understanding of our hearing system.

1. And that's exactly "the key thing" I brought up in my first post and which you disagreed with! "We are trying to understand" is quite different to "we completely understand" and complete understanding is what would be required in order to provide the absolute advice presented in many of the early responses to the OP to which I was responding.

2. How can I "continue to live in a stale world where lay intuition was used" when that's not the world I live in to start with? I do not pretend to have read all the research ever completed in the fields of acoustics and psychoacoustics, nor am I pretending to be able to perfectly accurately interpret and contextualise it all and therefore I don't claim to be the greatest expert on acoustics and psychoacoustics or even just an expert but likewise, I am certainly not just relying on "lay intuition" either. I have dug in and studied the field over the course of more than 25 years, much of that knowledge I have to apply everyday in my work and I've spent several hundreds of thousands of dollars of my own money over that period buying/applying acoustic treatment to my own studios, in consultation with highly respected acousticians.

G

 

[bigshot]

Sooner or later someone is going to read the subject title and tell him where to put his acoustic panels!

 

[amirm]

1. And that's exactly "the key thing" I brought up in my first post and which you disagreed with! "We are trying to understand" is quite different to "we completely understand" and complete understanding is what would be required in order to provide the absolute advice presented in many of the early responses to the OP to which I was responding.

Nope. Acousticians around the world design rooms everyday and twice on sunday based on this research. They are not waiting for more research to tell someone if they should or should not absorb lateral reflection points.

And what is the alternative? Believing junk science posted on forums without a citing of a single bit of research/controlled testing that it says it is true? Or following old folklore created in the 1970s around recording studio designs with horrible speakers confusing the facts? Is that what you are advocating or defending? Because that is what started this back and forth in this thread.

While research does continue in this field naturally, in some 40 years the beneficial aspects of some reflections has not been overturned. The research is durable because it aims to understand our hearing. Since we don't evolve that fast, it holds true.

By your logic, doctors shouldn't prescribe any medicine because we don't "completely" know every side effect they can have!

It is not an accident that I can quote paper after paper -- many of them peer reviewed -- to the efficacy of the research. The article I wrote which I referenced earlier (https://audiosciencereview.com/forum/index.php?threads/perceptual-effects-of-room-reflections.13/) was published years ago in Widescreen Review Magazine and it has been exceptionally received in the industry. When I go to shows invariably a speaker manufacturer remembers me from that article and praises the research within. Not one person has written in to say, "wait a sec, that is wrong!" It is only in the closed cacoon of forums that this happens.

2. How can I "continue to live in a stale world where lay intuition was used" when that's not the world I live in to start with? I do not pretend to have read all the research ever completed in the fields of acoustics and psychoacoustics, nor am I pretending to be able to perfectly accurately interpret and contextualise it all and therefore I don't claim to be the greatest expert on acoustics and psychoacoustics or even just an expert but likewise, I am certainly not just relying on "lay intuition" either. I have dug in and studied the field over the course of more than 25 years, much of that knowledge I have to apply everyday in my work and I've spent several hundreds of thousands of dollars of my own money over that period buying/applying acoustic treatment to my own studios, in consultation with highly respected acousticians.

Prior to 10 years ago, I was just like you. Then I sat through my first in-person presentation by Dr. Toole and it completely changed my views of acoustics Mind you, I was just as incredulous as you. I mean really... how could reflections from one angle sound different to us than another as Dr. Toole was explaining? So I set out to not only read Dr. Toole's writing, but dig through countless other research and papers. Here is a snapshot of my Acoustic folder:

(the creation date is after I organized them into one folder, not when I started to collect and read them).

As you see, it has incredible amount of content in it. More papers than I can possibly recount but I assure that it took reading them all, I realized that the "true north" as summarized so successfully by Dr. Toole was absolutely right.

You don't need to follow my long journey. Just read Dr. Toole's book. For $25 you will be the most educated person in audio in general, and sound reproduction in the specific. As an advocate of controlled/blind testing, he better be your hero as much as he is a mentor and good friend to me. Know that if you dig into 200+ references in his book, they will reinforce the same research. He knows what he is talking about for heaven's sake!

 

[gregorio]

Nope. Acousticians around the world design rooms everyday and twice on sunday based on this research. ... By your logic, doctors shouldn't prescribe any medicine because we don't "completely" know every side effect they can have!

Absolutely not! No vaguely competent acoustician should suggest acoustic treatment without analysing the room first and figuring out what problems need treating and no vaguely competent doctor would prescribe medicine without diagnosing the patient first. You though ... Seems your journey still has a way to go!!

G

 

[Strangelove424]

I've never seen someone try to prove their intelligence with folder sizes. That's rather pitiful, after it stops being funny for the first minute or two. The ego on display is alarming to behold, and almost makes me feel embarrassed for him.

 

[amirm]

Absolutely not! No vaguely competent acoustician should suggest acoustic treatment without analysing the room first and figuring out what problems need treating and no vaguely competent doctor would prescribe medicine without diagnosing the patient first. You though ... Seems your journey still has a way to go!!

Again, no. The "diagnostic" that your doctor is using is the same as the data that is present in front of an acoustician. You give him a room so he now has that data. You then ask him whether you should or should not block first reflection point. If they are old school like you, they will say "absolutely!" If they live in modern world I have been explaining, answer is, "if you are not a mix/recording engineer, you should leave those alone."

Go ahead and ask your competent engineers and post their reply here.

For now, my friend Ethan was put forward as one of these competent acousticians earlier in the thread. Here is what he has to say: http://realtraps.com/art_basics.htm

No mention of "analyzing" the room. You have to remember, I have debate this topic with top advocates of studio design. So please don't position them as something they are not. They absolutely have a design recipe in this specific area of acoustics we are discussing.

To provide some variety, here is Tony Grimoni on this topic. In case you don't know him, he is a very well-known high-end home theater designer. http://centurystereo.com/3882/room-acoustics-matter/

Again, advice given is absolute. No different than if you have the flu and you go to the doctor. Note that I do not agree with his view here even though he respects and agrees with much of what Dr. Toole advocates elsewhere

I have discussed these topics with numerous acousticians on both sides of the fence here. And what you describe is not correct at all. They are all strongly opinionated on these topics.

Yes, you want to measure things for full room design. Bass response for example is always wrong in rooms and there, measurements are critical to determine course of action (although some like Ethan say put bass traps there regardless). But in the narrow context of role of reflections above transition, what you state is not correct. It just isn't.