Side Wall, Floor and Ceiling Reflections - AVS Forum
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post #1 of 135 Old 06-27-2012, 05:03 PM - Thread Starter
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Most of the information I have read, strictly as an amateur, about reflections has had to do with side wall reflections, as do most of the treatments. Floor reflections and "floor bounce" have been occasionally brought up. I have read very little about ceiling reflections, possibly because they are so cumbersome to treat for non-professionals (or even for pros).

It'd seem that side wall, floor and ceiling reflections would have different characteristics, both physically and how the brain interprets them. Amir stated regarding floor reflections, "The answer had to do with the fact that the floor reflections come to our ear from a different angle and listening tests demonstrate that its effect is limited to higher frequencies." http://www.avsforum.com/t/1413173/does-sound-sounds-better-in-a-room-full-of-furniture-and-stuff-or-without Post #160.

Anyway I'd enjoy reading more about side wall, floor and ceiling reflections and if they require different treatments and how they affect what we hear.
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post #2 of 135 Old 06-27-2012, 07:00 PM
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There as red two thing you can do with ceiling - either use acoustic tiles suspended below hard ceiling, or use diffusers at first reflection points. You can start with diffusers, as this is easier to implement. If you are not satisfied, then go with tiles. You can check for reflections looking at impulse response in software like REW.
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post #3 of 135 Old 06-27-2012, 08:05 PM
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Quote:
Originally Posted by GGA View Post

I'd enjoy reading more about side wall, floor and ceiling reflections and if they require different treatments and how they affect what we hear.
Don't know if you've read Toole's (now infamous) final paper before he retired, but if you haven't, it is worth checking out here. Start at the end, sections 9.2.1 through 9.3, then go back and start reading at section 2.

The paper primarily deals with what listeners prefer when it comes to reflections, which points to historical data that can initially seem counterintuitive, until you factor in adaptation of our human hearing. You also have to put the notion of preferences into perspective. If you're human, then chances are good that your preferences will be similar to other humans. Hence data on listener preferences gives you a good starting point when it comes to understanding and treating reflections. But it doesn't guarantee that you will prefer the exact same things that most listeners did, any more than the song currently sitting at the top of the charts is guaranteed to be your favourite too. Treat it as useful info, not religion.

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post #4 of 135 Old 06-27-2012, 08:43 PM
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Sanjay-is this an excerpt from "Sound Reproduction: Loudspeakers and Rooms" or something entirely different?

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post #5 of 135 Old 06-27-2012, 09:02 PM
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Originally Posted by holt7153 View Post

Sanjay-is this an excerpt from "Sound Reproduction: Loudspeakers and Rooms" or something entirely different?
More like a shortened version that was later explored in far greater detail in 'Sound Reproduction'. By the end of the paper, Toole drops the hint that the paper wasn't intended to be conclusive but instead raise questions and encourage more research. Hence my comment about it being a good starting point.

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post #6 of 135 Old 06-28-2012, 08:23 AM
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In order to prevent another thread implosion, might I suggest the whole topic of whether or not reflections are good or bad be avoided? (As much as possible at any rate). Or perhaps its just me suffering from Toole Burnout smile.gif

Rather, the context should be of what *relative* importance is treating ceiling reflections, vs side or floor reflections, and what the relative differences are between them.
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post #7 of 135 Old 06-28-2012, 09:13 AM
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Originally Posted by kromkamp View Post

Rather, the context should be of what *relative* importance is treating ceiling reflections, vs side or floor reflections, and what the relative differences are between them.
How would you decide relative importance in order to prioritize treatment?

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post #8 of 135 Old 06-28-2012, 09:47 AM
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Well I suppose the answer should be derived from how our ears process sound coming from the sides, vs from above or below. I suppose the answer should also reference the typical off-axis performance of speakers horizontally vs vertically.

Also, for a typical residential room, the ceiling or floor reflection will arrive much sooner after the direct signal than the sidewall reflections, unless you are sitting very close to the wall. This might also inform the answer.

In my own situation I am getting ready to tackle ceiling reflections, but there are certainly challenges (aesthetic and otherwise) involved. For example my ceiling mounted projector is at the location of specular reflections from the center channel. So this topic is of particular interest to me as well.
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post #9 of 135 Old 06-28-2012, 10:51 AM
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Quote:
Originally Posted by GGA View Post

It'd seem that side wall, floor and ceiling reflections would have different characteristics, both physically and how the brain interprets them.

I doubt this has anything to do with hearing differently based on the angle of arrival. Either way the result is comb filtering - a skewed response of the direct sound with the peak and null frequencies based on the distance. More likely it's related to the way loudspeakers disperse horizontally versus vertically. Most speakers are designed to spread sound outward horizontally over a wide arc, but much less so vertically. Assuming the tweeters are at ear level for people seated on a couch, the floor is at a shallower angle than the ceiling. So carpet or throw rugs are useful to absorb those reflections. The ceiling is usually much higher and thus farther from the tweeters. That said, my living room HT has absorption on the sides walls, carpet on the floor, and also absorbers on the ceiling.

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post #10 of 135 Old 06-28-2012, 12:28 PM - Thread Starter
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Originally Posted by sdurani View Post

Don't know if you've read Toole's (now infamous) final paper before he retired, but if you haven't, it is worth checking out here. Start at the end, sections 9.2.1 through 9.3, then go back and start reading at section 2.
The paper primarily deals with what listeners prefer when it comes to reflections, which points to historical data that can initially seem counterintuitive, until you factor in adaptation of our human hearing. You also have to put the notion of preferences into perspective. If you're human, then chances are good that your preferences will be similar to other humans. Hence data on listener preferences gives you a good starting point when it comes to understanding and treating reflections. But it doesn't guarantee that you will prefer the exact same things that most listeners did, any more than the song currently sitting at the top of the charts is guaranteed to be your favourite too. Treat it as useful info, not religion.

Thanks Sanjay. Very interesting reading and your summary is very well stated.
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post #11 of 135 Old 06-28-2012, 03:23 PM
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My (limited) experience, fwiw. I first put up absorbers (4" thick 703 type stuff) on the side walls at first reflection points.
Then later I put up ceiling absorber (2-6" thick for visual reasons) at first reflection points.
Adding the ceiling absorber helped in my room with my speakers (B&W 703 - which I think might have some
weird dispersion patterns around the 4khz crossover). Room is plaster over metal mesh lathe.
Adding big blocks (16"x20"x24" of 703 type stuff) on the floor between me and speaker
was not as useful as covering those same blocks with a garbage bag and putting them on the floor/wall
corner - along with other corner treatments in an attempt to damp room modes).
Sometimes you just have to play with what works in your room, for your ears, and preferences.
Most people's ears are symmetrical right and left, but asymmetrical top to bottom - probably not an accident.

(in my 5.1 room - an addition with typical studs/drywall construction - I found I didn't need any treatment
to get acceptable sound - but I'm less critical of sound in that room, so who knows . . .)

edit - I haven't tried comparing just ceiling treatment to just wall treatment - but for me
adding ceiling treatment helped a lot

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post #12 of 135 Old 06-28-2012, 06:12 PM
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Originally Posted by kromkamp View Post

Well I suppose the answer should be derived from how our ears process sound coming from the sides, vs from above or below. I suppose the answer should also reference the typical off-axis performance of speakers horizontally vs vertically.

Also, for a typical residential room, the ceiling or floor reflection will arrive much sooner after the direct signal than the sidewall reflections, unless you are sitting very close to the wall. This might also inform the answer.
Understood, but after you find out how our ears process sounds from different direction (which, BTW, has already been researched pretty heavily), what will you use to decide relative importance? That is, on what basis would you choose to prioritize treatments? In other words, what would make the top of your list (treat first) vs the bottom of your list (low priority) when deciding relative importance? That's what I was curious about when I asked you earlier.

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post #13 of 135 Old 06-28-2012, 10:57 PM
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From psychoacoustics point of view, ceiling reflections are a bit of an enigma. One would normally expect the ear/brain to no be hardly sensitive to them as the same sound is reached both ears unlike side reflections (i.e. what happens due to front wall reflections). Listening tests by both Harman and Rakerd, et al. however show that the threshold of detection is actually the same as side reflections. Why the brain is more sensitive when the vertical angle is increased is not very clear. This is the hypothesis by Rakerd paper: (HP means horizontal plane/side reflections and MSP is median sagittal plane/Ceiling reflections)

"The present psychophysical findings of equivalence in echo suppression for the HP and the MSP can be interpreted two ways. It is possible that the suppression occurs at a neural processing site that is indifferent to source location. Alternatively, the findings may be seen as consistent with recent neurophysiological evidence ~Litovsky and Yin, 1994; Yin and Litovsky, 1994; Litovsky et al., 1997! for an echo suppression mechanism mediated by higher auditory centers where binaural and spectral cues to location are combined."

While echo suppression is the same as side reflections, the audible effect is limited to timbre change only. I.e. no increase occurs as far as speciousness and such (i.e. it is not a beneficial reflection). Dr. Toole's optional recommendation is to use a diffuser to push the reflections to the side walls. Keith Yates is also a fan of diffusion in the ceiling. Tony Gremoni suggest an absorber although he leaves the option for diffuser.

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post #14 of 135 Old 06-29-2012, 03:54 AM
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Originally Posted by amirm View Post

From psychoacoustics point of view, ceiling reflections are a bit of an enigma. One would normally expect the ear/brain to no be hardly sensitive to them as the same sound is reached both ears unlike side reflections (i.e. what happens due to front wall reflections).

"One would expect?" I simply don't get this. I see no reason why a reflection of a certain amplitude and incorporating a certain delay would be perceived in a significantly different way simply because of the direction from which it arrives at the listener, particularly when this direction is within the front hemisphere of hearing.
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Listening tests by both Harman and Rakerd, et al. however show that the threshold of detection is actually the same as side reflections. Why the brain is more sensitive when the vertical angle is increased is not very clear.

The above two sentences appear to contradict each other. The first sentence says that the "the threshold of detection is actually the same", and the second sentence says that "The brain is more sensitive when the vertical angle is increased". If one believes the first statement is true, then the second statement has to be false. Gibberish!

Due to the way that the head and pinnae affects the sound field at the ears, there are differences in the amplitude and timing in the acoustical signal that reaches the left and right inner ear. However, these differences are not huge.

http://interface.cipic.ucdavis.edu/sound/tutorial/hrtf.html:

231

From this we see that the response of the ear is a strong but not overwhelming function of azimuth. Having a sound arrive from a different angle causes audible differences, but it does not attenuate these sounds to the point where they are surely inaudible.

In the median (vertical) plane, we see a similar pattern:

376

There are variations that are sufficient to be readily perceived as differences, but sounds from off-axis are not extinguished.

Thus to a large degree, a reflection whose amplitude and timing is in a certain range has similar effects regardless of the direction it comes from. This agrees with the theory that hearing evolved for the purpose of improving the survival rate of humans - we hear threats to a great degree no matter which direction they come from.
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post #15 of 135 Old 06-29-2012, 07:14 AM
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Originally Posted by arnyk View Post

"One would expect?" I simply don't get this. I see no reason why a reflection of a certain amplitude and incorporating a certain delay would be perceived in a significantly different way simply because of the direction from which it arrives at the listener, particularly when this direction is within the front hemisphere of hearing.
The case of ceiling reflections is indeed puzzling in part because of the explanation is in the data you presented. That is, if a reflection is coming from say the right, the left ear hears it differently because its spectrum will be modified by your head. It will also be delayed about 0.4 milliseconds. The brain then is forced to interpret what the two differing signals from each ear means. It appears to do so by ignoring most of such differences and instead of providing confusion, conveys a feeling of spaciousness and hence realism to the direct sound coming from the speaker. When the reflection comes directly from the above front, then the two ears hear the same thing. Therefore, one would expect it to behave more in line with the reflection from front wall than the side. Well, listening tests show otherwise and hence my use of the word "enigma." Here is a quick graph to demonstrate that:

i-cd4h8QV-X2.jpg

We see the threshold at which we detect any change to the sound due to reflections is very similar for the side and high up (lower dashed graphs) and both distinctly different than coming from where the speaker is (top graph). So somehow the ear+brain combo is putting higher value in hearing that ceiling reflection. Note that comb filtering is occurring in all cases yet the perceived effect is very different.
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The above two sentences appear to contradict each other.
Per above, they were meant to smile.gif.
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Due to the way that the head and pinnae affects the sound field at the ears....
Those are measurements in the graphs you post. They are devoid of how the brain interprets the signal (they are also devoid of torso effect). To be sure, they are good indicator of differences that exists due to the shape of our ears, head, they don't ultimately tell you what the brain does. That is why listening tests are performed. In this instance, the measurements and listening tests do not agree. Why I don't know smile.gif. It simply is the case based on data at hand.
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there are differences in the amplitude and timing in the acoustical signal that reaches the left and right inner ear. However, these differences are not huge.
No statement was made about hugeness. What is hugely clear is that we do not hear such reflections as echos due to the timing and levels that exists in our home listening space. So it is all about subtle interpretations by the brain as to what the reflection does to the direct sound. The sense of spaciousness that comes from side reflections for example is indeed small. So small that if you have a multi-channel system/content, what is recorded in there as far as ambiance, overwhelms the bit that the walls provide. In 2-channel listening however, such secondary cues don't exist so there can be a case made for putting diffusers at the side reflection points to enhance them. For multi-channel is it is not necessary although a case can be made that the center speaker carrying the dialog at a single point where it is sitting, could benefit from some widening of its apparent location with side reflections as to better cover the full video screen.
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Thus to a large degree, a reflection whose amplitude and timing is in a certain range has similar effects regardless of the direction it comes from. This agrees with the theory that hearing evolved for the purpose of improving the survival rate of humans - we hear threats to a great degree no matter which direction they come from.
Remember, this is not about hearing just the reflection. It has to do with a reflection at a different level and timing combining with the direct sound. The investigation is into at what level we hear that at all (below which it might as well not be there). Above that threshold there are usually two other thresholds. At the other extreme there is a level at which we hear it as a distinct echo which is bad. And there are other thresholds in the middle such as that enhanced realism/image widening that for example happens for the side reflections. So while you are probably right that what we hear is a matter of evolution, the subject here is different than hearing sounds *source* from other directions. We are dealing with much more complex situations of sounds combining from different directions.

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post #16 of 135 Old 06-29-2012, 07:33 AM
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Quote:
Originally Posted by kromkamp View Post

In order to prevent another thread implosion, might I suggest the whole topic of whether or not reflections are good or bad be avoided? (As much as possible at any rate). Or perhaps its just me suffering from Toole Burnout smile.gif
Rather, the context should be of what *relative* importance is treating ceiling reflections, vs side or floor reflections, and what the relative differences are between them.
The relative importance for ALL reflections pales in comparison to optimizing the low frequencies. If you want priority, that is where you want to focus. The reason is simple and has to do with the effect of the room has over the sound of the speaker:

Room-Speaker-Effect.png
Look at how smooth and (relatively) clean the high frequency response is despite the speaker being in a room rather than in anechoic chamber. Now compare that to frequencies below the transition frequencies. They not only go up and down by huge amounts but also vary substantially in seat by seat. That is why the graph says the room is in control of the sound you hear.

Unfortunately for some reason in forum discussions all the energy is put on debating and worrying about reflections and such. Maybe because we have more intuition about that which sadly, is the wrong kind of intuition relative the research smile.gif. Your goal above the transition frequency simply needs to be that your room is not overly live or dead. Get it out of those two regions and you are most of the way there. The next priority must be then on low frequency optimizations which thankfully can be measured simply as done above with a frequency response graph and we need not concern ourselves with psychoacoustics. Only after you have optimized the low frequencies do you want to look at what these reflections mean. You can read Dr. Toole's paper as posted earlier on that topic, or better yet his book and best of all, in person at CEDIA conference. Alternatively here is a quick primer to better introduce the problem with good bit of measurements thrown in there to quantify what can be done: http://www.madronadigital.com/Library/BassOptimization.html.

My apologies for mentioning Dr. Toole's name to you smile.gif. Folks disagree a lot in this space but one thing few disagree with is the role that he/Harman have played in teaching us the science of low frequency optimization in our homes. Techniques presented in that article have unified support among professionals.

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post #17 of 135 Old 06-29-2012, 08:20 AM
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Quote:
Originally Posted by arnyk View Post

I see no reason why a reflection of a certain amplitude and incorporating a certain delay would be perceived in a significantly different way simply because of the direction from which it arrives at the listener, particularly when this direction is within the front hemisphere of hearing.
I was perusing a paper recently that briefly encapsulated what direction has to do with reflections. Dirac on RC & EQ.pdf 351k .pdf file
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There seems to be consensus in the field that some early reflections actually help make speech more intelligible. However, it is also well documented that reflections within 5-10 ms of the main pulse in typical listening rooms are above the level where the primary source shifts or spreads (even when just listening to a single primary source). Reflections from the front and the rear (within ±40º) are perceived as detrimental to sound quality, whereas side reflections (within reasonable levels) often improve the perceived sound quality.

This can be understood from an information-theoretic perspective. Reflections that come from the front are typically very hard to distinguish from the primary source due to the placement of our ears. The transfer function of an individual front reflection is nearly the same at the left and the right ear, just like the response of the primary source. Indeed, this is the reason why a filter can correct for these reflections robustly. They are constant in a relatively large listening volume! Contrast this with reflections from the side. Such reflections vary much more with position due to the angle of incidence. There is always a big difference at the left and the right ear, and consequently side reflections give a diversity gain. Diversity is an information-theoretic concept that quantifies the number of distinguishable communication channels. The higher the diversity, the higher the Shannon capacity of the information transfer. This is utilized in mobile wireless communication systems where reflections that are independent of the direct path are used to actually increase the bit rate of the system. There is also an interesting corollary that reflects the detrimental effects on human auditory perception by front and rear reflections. Since these channels cannot be distinguished from the primary source (both are nearly constant), these channels simply cause self-interference. In the capacity formulas, this translates directly to lower signal-to-noise ratios, and lower capacity of the information transfer.
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post #18 of 135 Old 06-29-2012, 02:35 PM
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Originally Posted by sdurani View Post

The paper primarily deals with what listeners prefer when it comes to reflections, which points to historical data that can initially seem counterintuitive, until you factor in adaptation of our human hearing. You also have to put the notion of preferences into perspective. If you're human, then chances are good that your preferences will be similar to other humans. Hence data on listener preferences gives you a good starting point when it comes to understanding and treating reflections. But it doesn't guarantee that you will prefer the exact same things that most listeners did, any more than the song currently sitting at the top of the charts is guaranteed to be your favourite too. Treat it as useful info, not religion.
Thank you for taking such a reasoned approach to Floyd Toole's findings. It is a breath of fresh air around here, being free from dogmatic pronouncements.
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post #19 of 135 Old 06-29-2012, 07:38 PM
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Many good points.

I've measured, I experimented with models,... I've found in my current room, I prefer my ceiling area between the primary LP and the mains to be aggressively treated with absorption. I would like to experiment with redirection, as AVS member Kevinzoe recommended to me nearly two years ago. But I've swapped out mains in experimentation, etc, and seemed to prefer the ceiling, between me and the LCR's, to be well damped acoustically. I tried variety of sidewall approaches, yet retained this approach throughout experimentation.

I've settled on new mains and take delivery any day. I will re-visit, re-evaluate the ceiling treatment and proceed accordingly again.

Thanks

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post #20 of 135 Old 06-29-2012, 10:53 PM
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Thank you for taking such a reasoned approach to Floyd Toole's findings. It is a breath of fresh air around here, being free from dogmatic pronouncements.
You're welcome. Believe it or not, that's Toole's approach as well. If you read his book, you'll see that it's all about direction, not destination.

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post #21 of 135 Old 06-30-2012, 06:16 AM
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You're welcome. Believe it or not, that's Toole's approach as well. If you read his book, you'll see that it's all about direction, not destination.
You'd never know it given the zealotry exhibited by Toole's advocates here.
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post #22 of 135 Old 06-30-2012, 07:17 AM
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You're welcome. Believe it or not, that's Toole's approach as well. If you read his book, you'll see that it's all about direction, not destination.
I don't know how you could say that Sanjay. If you sit through a presentation with him, or speak to him, you see that the case he presents is anything but directional. He will demonstrate his case to you with extreme conviction. He will tell you in extremely direct manner how many of the current assumptions about acoustics are flat wrong. And he doesn't just preach, he practices what he says. Take a look at Sean Olive's AES paper on the reference listening room they built. It is a complete mirror of the recommendations in the AES paper and book. He allocates considerable amount of time to this topic in his presentations and frankly, you can't leave the room until you concede smile.gif. As to the book, there are a ton of that in there too with this topic taking more than one chapter. Here are some choice comments from it:

"9.1 THE AUDIBILITY OF ACOUSTICAL INTERFERENCE—COMB FILTERING
The term comb filtering just in itself sounds ugly. And its physical appearance,
a succession of deep notches, looks ugly. And ugly is bad, so comb filtering must
be bad. But if this is the prosecution’s argument, they lose! The defense can call
witnesses, many who will have impressive academic credentials, and many,
many more who are just ordinary listeners but can attest to the audible innocence
of this phenomenon. Many of them will claim that, in some situations,
comb filtering sounds good—and under oath, too!"


How could anyone take this as directional? It is not directional. He is saying that the current positions such as what Ethan took earlier in this thread that reflections cause comb filtering and hence have to be done away with are wrong.

In another section he says this:

"The upshot is that, in any normal room, audible comb filtering is highly
improbable. The less “live” the room, the more likely it will be that even a single
reflection can be audible as coloration. This is a good point to look at again in
Figure 9.3. Measurements don’t lie, but some of them, like these, are not the
most direct path to the truth that matters: what we hear. The reflections that
cause comb filtering are the same refl ections that result in the almost entirely
pleasant, pleasurable, and preferable impressions of spaciousness discussed in
the previous two chapters."


I didn't want to post all of this before when you first made the statement as someone said not to but please, let's not change the man's stance for the sake of it. And it is not just him. If you sit through presentations from other Harman researchers, you see the same conviction here. Alan Devantier will tell you the same thing. Here is Sean Olive in his AES paper on the design of their reference room:

"The placement of the acoustical panels in the reference
listening room shown in Figs. 4 (a) and (b) is based on
the scientific rationale proposed by Toole [1]. In order
to encourage spaciousness (broadening of the apparent
source width) the sidewalls are left untreated at the
point where the first lateral reflections produced by the
front channels arrive at the listening location."


So maybe you have a different definition of "directional" than I do. I don't consider any of this directional. Perhaps you mean that they leave room for someone doing different. Yes, they do. They will tell you that they are wrong but that there is no reason to call the police on them smile.gif.

I have repeatedly said that it is fine to disagree. But let's disagree after we familiarize ourselves with the research data as it exists. Let's not go by our intuition which can't possibly predict how our hearing and brain work. Let's not stick our head in the sand and ignore the research because we like to think it is less definite than it really is. The evidence is highly compelling and strongly presented -- more strongly than I have seen just about anyone do.

And why the resistance? It is not like he is saying unless you put up diamonds on your wall you are going to get bad sound. He is saying you can put furniture in a room and have it nicely approximate what would happen with acoustic products. He says you don't have to stick fiberglass on the side walls of your living room. It says we don't have to go and learn new tools like ETC. The answer is that there is a ton of goodness here for us as consumers. The resistance then comes from us not wanting our previously stated convictions demonstrated to be wrong. Fine. That is how we act as humans. But if we want to search for the truth, we want to reserve the right to get smarter smile.gif. I did that. Not sure why it is so hard for others to do the same. I know you are most of the way there with these thoughts. I just want to make sure people don't go using your statement above as an excuse to ignore what is being taught here as I see Audiosavant doing already. Anyone who doubts any of this can buy the $44 book and see for themselves.

So no, he doesn't call the police on you if you go and absorb first reflections, run ETC, etc. If that is what you mean by "directional," sure. It is not my definition of the word however.

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post #23 of 135 Old 06-30-2012, 09:01 AM
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I don't know how you could say that Sanjay...

So no, he doesn't call the police on you if you go and absorb first reflections, run ETC, etc.

Sanjay, amirm is in denial that Toole said the following:

""The real solution, for professionals as well as consumers, is loudspeakers that deliver similarly good timbral accuracy in the direct, early reflected and reverberant sound fields. This can be described as a loudspeaker with a flattish, smooth, axial frequency response, with constant directivity (which together result in flattish, smooth, sound power). Then it becomes an option, whether the room is acoustically damped, or not. If reflected sounds are absorbed, the listener is placed in a predominantly direct sound field, making the experience more intimate, and the imaging tighter and more precise. If the reflections are allowed to add their complexity, the overall illusion is altogether more spacious and open, to many listeners, more realistic. In part, this is a matter of taste. In either case, a room-friendly loudspeaker will yield timbral accuracy. So, at middle and high frequencies, the proper solution to getting good sound quality, is to choose good loudspeakers to begin with."
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"Then it becomes an option, whether the room is acoustically damped, or not. If reflected sounds are absorbed, the listener is placed in a predominantly direct sound field, making the experience more intimate, and the imaging tighter and more precise. If the reflections are allowed to add their complexity, the overall illusion is altogether more spacious and open, to many listeners, more realistic. In part, this is a matter of taste."
Exempli gratia:

Toole's former protege Kevin Voecks, manager of product development for Harman's Luxury Audio group, himself "disagree(s)" with Toole in that Kevin prefers absorption at sidewall reflection points.
Home Theater Geeks Podcast 90: Kevin Voecks start at ~22:00 mark.
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Exempli gratia:
Toole's former protege Kevin Voecks, manager of product development for Harman's Luxury Audio group, himself "disagree(s)" with Toole in that Kevin prefers absorption at sidewall reflection points.
Home Theater Geeks Podcast 90: Kevin Voecks start at ~22:00 mark.
That is true. Kevin does disagree. As I noted, once you know the science and then disagree, all is well. But please don't skip that step.

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Sanjay, amirm is in denial that Toole said the following:
"The real solution, for professionals as well as consumers, is loudspeakers that deliver similarly good timbral accuracy in the direct, early reflected and reverberant sound fields. This can be described as a loudspeaker with a flattish, smooth, axial frequency response, with constant directivity (which together result in flattish, smooth, sound power). Then it becomes an option, whether the room is acoustically damped, or not. If reflected sounds are absorbed, the listener is placed in a predominantly direct sound field, making the experience more intimate, and the imaging tighter and more precise. If the reflections are allowed to add their complexity, the overall illusion is altogether more spacious and open, to many listeners, more realistic. In part, this is a matter of taste. In either case, a room-friendly loudspeaker will yield timbral accuracy. So, at middle and high frequencies, the proper solution to getting good sound quality, is to choose good loudspeakers to begin with."
As I noted, the sum total of my knowledge about Dr. Toole's views are not limited to such one-liners in online articles. If someone has likewise talked to Dr. Toole and thinks he is all OK with folks doing what they like, let's hear it. What is ironic is that Dr. Toole is probably the most quoted expert in this forum yet folks refuse to read or listen to much of what he has to say. In all this time, I have only run into one other person who has actually taken one of his classes. This is the interchange on that with another poster claiming to know Dr. Toole's views better:
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If you get the opportunity, I suggest hearing him in person He says more than that. This is from his CEDIA course on "Room Accoustics Demystified: "A well-furnished lving space (carpet, sofa, chairs, drapes, bookcases and cabinets) can be an excellent listening environment." He spends quite a bit of time emphasizing this.His main use of room acoustics if for dedicated rooms/listening spaces which by definition are devoid of typical things he mentions there.That's right although most of his worry is not "over-applying" but using too thin of material which includes just about most treatment people slap on the walls. You can complain about AJ but he has read Floyd's work. You are not going to invalidate what AJ says using the same source.

The above was quoted by Randy with this response:
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I went to one of his CEDIA courses and that is pretty much dead on.

Doesn't look like that I am making stuff up about what he says now, does it?

Back to the quoted paragraph, you accept the sentence I bolded?

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Back to the quoted paragraph, you accept the sentence I bolded?

Yes, according to Toole, some people prefer "the overall illusion is altogether more spacious and open, to many listeners, more realistic"; others prefer "predominantly direct sound field, making the experience more intimate, and the imaging tighter and more precise." Toole allows for both, saying that it is largely a matter of taste.

The issue should not be which we should prefer, but rather how to achieve that which we do prefer. If I prefer the later, I should not then be forced to fill my listening room with overstuffed sofas, arm chairs, end tables, bookcases, curtains and brick-a-brac in a helter-skelter effort to approximate a well damped room, but instead be permitted to apply broadband absorption to walls and ceilings to achieve my desired goal using the methodologies outlined here by your arch-nemeses dragonfly and localhost127.

When Harman designed their latest listening room, they had a choice on how they would treat it. They chose not to fill it with overstuffed sofas, arm chairs, end tables, bookcases, curtains and brick-a-brac as you advocate, but rather used broadband absorption and diffusion panels on all walls. Ironic, isn't it.
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Yes, according to Toole, some people prefer "the overall illusion is altogether more spacious and open, to many listeners, more realistic"
Come again? It is both "some people" and "many listeners" at once? Many = Some in your book? And why do you say according to Toole? I am asking if you agree with that statement or not. We know what he has written and don't need you to rewrite it for us smile.gif.
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The issue should not be which we should prefer, but rather how to achieve that which we do prefer.
And in what manner have you determined what you prefer? Reading forum posts? Going by your gut that a reflection must be bad? A meter that told you that? Or did you sit in an anechoic chamber and simulate what happens when a reflection is there vs not?

Earlier I post the threshold of detecting a reflection coming from different angles. You would have intuited that without the listening tests? If so, you are smarter than the rest of us combined smile.gif.
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If I prefer the later, I should not then be forced to fill my listening room with overstuffed sofas, arm chairs, end tables, bookcases, curtains and brick-a-brac in a helter-skelter effort to approximate a well damped room, but instead be permitted to apply broadband absorption to walls and ceilings to achieve my desired goal using the methodologies outlined here by your arch-nemeses dragonfly and localhost.
My arch-nemeses? I love those two guys! Without them we wouldn't have these discussions. Someone has to play that role. Sure, we could all do with less insults and more constructive discussion but please don't confuse this as some kind of personal fight for me. My passion is in discussing the technology and I have no ill feeling about the individuals at all. What you want to say is that they take the opposing view and that they do. As I noted, they are in the same group of people who quote snippets of Dr. Toole's teachings but as soon as they are exposed to more, they immediately back off, call him a non-expert, and his opinion not worthy of attention. Dragon calls listening tests that he performs and that of other researchers as "surveys and polls." Is that what you think of audio listening tests? How about their results? He calls them marketing brochures. Are they?

Importantly, they never, ever put forward listening test results or measurements of anything they have done. No pictures. Nothing. If you prefer to listen to them instead of Dr. Toole which showers you with data and back up, who am I to complain smile.gif.

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Sure, we could all do with less insults
You brought it onto yourself with your intentional deflection, redirection, complaints and making things up as you go (a k a dance).
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post #30 of 135 Old 06-30-2012, 04:16 PM
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Understood, but after you find out how our ears process sounds from different direction (which, BTW, has already been researched pretty heavily), what will you use to decide relative importance? That is, on what basis would you choose to prioritize treatments? In other words, what would make the top of your list (treat first) vs the bottom of your list (low priority) when deciding relative importance? That's what I was curious about when I asked you earlier.

If you are asking me specifically, the answer is I won't - my walls are already treated, and I am now deciding what amount (if any) and what type of treatment to use on the ceiling.

I don't think the relevant question is what priority to assign treatments on different surfaces (like if your budget is limited or something) - rather the question is what type/quantity of treatment is appropriate for each surface. I apologize if my statement of "relative importance" suggested otherwise (as I could see how it could, perhaps a poor choice of words on my part)
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