Acoustic treatment for my living room - Page 6

"What the data shows is what happens when you go from no absorbers to many. Localhost then point to the time domain chart and say, "see, it is a lot cleaner." Folks like yourself trust your gut and proceed to believe something good has happened. It is a wonderful campaign because folks put aside all science and believe what visually looks convincing.

Let's see if the graph proves that bad speakers can be fixed this way, this time, focusing on the best case scenario with maximum number of absorbers..."

A classic case of not having a clue as to what 1.) was the purpose of the exercise (despite description) and 2.) erroneous conclusions based upon having no clue regarding what the example attempted to show.

Which should serve as a most adequate example of how additional conclusions should be interpreted in light of such glaringly incorrect interpretations.

First, the example has NOTHING to do with the speaker response. It could be a unit with the most amazing response in the universe or the worst, or anywhere in between. The issue is superfluous.

The purpose of the example is simply to show the effect of removing non-minimum phase reflections by incrementally applying absorption to incident boundary points, thus showing the corresponding 1:1 reduction in resultant comb filtering as a result of the reduced superposition of direct and indirect signals displayed in the time domain.

There is NO other purpose to the example than this. It does not propose to suggest an acoustical response goal of any type. It simply illustrates the nexus between the causal superposition of direct and indirect signals and the resultant frequency comb filtering, and to illustrate that is the superposition of direct and indirect signals is reduced or eliminated, that the derivative comb filtering is reduced.

Also, the example has absolutely no connection in any way to LEDE/RFZ. NONE. There is absolutely no reason for that term to even be mentioned, except that someone apparently hallucinates a nexus. Aside from bearing absolutely no semblance to the acoustical response model, anyone with half a clue regarding LEDE would know that any signals outside the ISD are mitigated with diffusion. A similarly absurd nexus could also be made with chocolate chip cookies.

And I will go one step further to categorically state that it is NOT a correct procedure to attempt to remove every reflection! Again, this example was performed simply to provide a visual reinforcement of the concept that by removing indirect reflections, that the resultant comb filtering is reduced. In fact, all reflections are not evil and all comb filtering is not detrimental.

The example merely systematically illustrates the progression from an example illustrating the response for a particular speaker in a particular room, and then proceeds to move from an untreated space complete with comb filtering, to a predominantly dead space, removing reflections and illustrating that as the individual reflections are removed, that the degree of comb filtering is also reduced.

It shows HOW the cause (indirect reflections) and the result (an interference pattern called comb filtering) is related. Nothing more, nothing less.

The example also does not make any attempt to recommend any type of treatment response.

And to clarify for anyone who has mistakenly assumed that anything asserted above regarding absurd claims that room treatment will somehow correct for a speaker's direct response, there is NO claim whatsoever that room treatment corrects for the source's direct signal character. Such a notion is 100% FALSE. The use of absorptive treatment strategically placed simply removes anomalies introduced by room-speaker (direct - indirect) signal interaction (superposition).

It is completely incorrect to assert that room treatment in any way corrects for the character or quality of a speaker's direct signal. Unfortunately, exactly such a thing has incorrectly been asserted here.

Please do not let this misinterpretation cause any confusion.

What happens if after the treatments are done, Audyssey is run?

I have no idea what hallucinating a nexus is. But it doesn't sound too good! So in my defense, I put forward this article: http://jgbouska.tripod.com/audio/d_d...io_1987_p1.pdf

Title: "The LEDE Concept"
Author: Don Davis

"An excellent example of the former approach is shown in Fig. 11 which illustrates how Doug Joes of Electro coustic Systems made an ordinary room meet this particular part of the LEDE room."

Let's look at defense Exhibit A again:



It is Fig. 11. And exact copy of what is in that article on page 54.


Amen brother .

Wonder why you had said this earlier though when you first introduced this graph into the conversation:


So it was an example of something bad then, but not now? I take the "now" answer as that follows the research I quoted in the other thread .


Not at all .

First, what is posted is NOT "Fig. 11. And exact copy of what is in that article on page 54." "And exact copy"???? What is posted is an edited copy and as such is absolutely NOT what Doug created nor that which Don utilized. As neither person was stupid enough to attempt to claim that the mitigation of comb filtering by addressing indirect reflections would in any way modify the direct signal of the speaker itself. For you see, Don was an adamant proponent that the quality of the speaker and the nature of its controlled Q/dispersion was an essential fundamental concern before all else. And I have documents stating this assertion that go back to the mid 1970's, before Toole was even out of school. Amazingly, this same concern was advocated by others such as Hidley who was directly responsible for the development, along with Kinoshita of TAD, for the famous Hidley/Kinoshita monitors that were fundamental to the Hidley and Newell NE rooms (and that, as I suspect few here are familiar with them, are still sourced by Reys Audio). "Funny how", to quote Don, "the ancients keep stealing all of our inventions..."

But let's quote the PROPER context of the example:

Figure 9-22 shows a cutaway view of a small room with a loudspeaker in the corner. Figures 9-23 through 9-28 show Sonex being added and the effect of each piece of absorption measured. Note that all reflections were removed (in his time window) without total absorption in the front of the room. Of course a control room is much more complex. p. 224, Sound System Engineering, 2nd edition, 1987 Davis & Davis

So the example shows the effect of each piece of absorption added mitigating actual reflections and the effect on the frequency response, effectively minimizing the contribution due to high gain reflections. Hardly what was mis-characterized above!

The cited example has NO necessary connection to LEDE/RFZ except to illustrate a general technique of identifying the effect that various indirect signals can have on the resultant frequency response as a result of superposition of high gain indirect signals with the direct signal. We will also note that it is specifically related to two channel reproduction. A distinction at least one misses as they consistently misrepresent alternative points of view.

Funny, I have the ORIGINAL source documents from where the example comes. I was even present in the sessions where the concepts were presented. I will also say that Alton Everest did a much better job of collecting and editing the materials into the Master Handbook of Acoustics where the overwhelming majority of the data and materials were sourced directly from SynAudCon functions than does a particular party here who has trouble selectively editing individual documents for meaning. Don also referred to Doug's example later both in the 2nd edition of SSE as well as in the LEDE Concept paper published in Audio - a paper that served as the first introduction for many of the effects of reflections, that ironically was also misinterpreted by many to mean that reflections were evil and that absorption was a sufficient solution to 'eliminate' reflections. Ironically, it seems that the misinterpretation of the article continues to this day, while these same folks will then pretend to tell those of us who DO understand the concept what it means.

I was also involved in many of the workshops and seminars from which these applied concepts originated, and I can tell you that NO ONE came out of those sessions with such a whacked perspective on the articles, concepts or acoustical tools.

And while the technique itself has NO NECESSARY connection to LEDE/RFZ, the technique can absolutely be used in the process of affecting the treatment of LEDE, insofar as this is an example of the technique that is employed in greater detail and in a more targeted manner to achieve the desired acoustical response in the room.

The irony is that ANYONE with half a brain who actually knows what the acoustic response of an LEDE/RFZ ETC response would mistake the response evident in the cited example in Doug Jone' concept example with LEDE/RFZ, as it is RADICALLY different from the fundamental criterion required by LEDE/RFZ. As no one familiar with LEDE/RFZ would ever use absorption to mitigate later arriving energy which is DESIRED in the LEDE/RFZ model!

Only one totally unaware of what LEDE/RFZ is could mistake a response such as that exhibited in the simple example illustrating the relationship between indirect reflections and comb filtering that bears absolutely no resemblance to the acoustic response required by the LEDE/RFZ model that is anything BUT a dead room as the ETC from the example shows.

But I am sadly confidence based upon precedence that the obfuscation and mis-information exhibited in such erroneous claims will not be the last, seeing as how they form a continuing basis for much of the imagined arguments.

You see, for some folks who lack an actual understanding of a concept simply lift sentences out of context as they glibly pretend to be able to tell us what a particular response model is, simply utilizing a technique apparently qualifies anyone to become an artisan despite lacking the knowledge and ability, and thus mistake the simple possession of a tool with the acumen and insight to apply the tool properly. Such is the insight that equates a simple process that may be used as a tool to help achieve a particular acoustical response, with the assumption that simply by possessing the tool, that any result will actually achieve a particular acoustical response.

Just as some, by virtue of having read an article or two, now feel competent to tell others that they must design, treat, and achieve an amorphously defined Toole/Harmon room (for which they cannot provide an accurate acoustical response model) that is totally dependent upon the power response of a speaker, ironically the very same type of relationship that Toole so loudly and absurdly laments for other models.

As is easily evidenced here, it takes more than simply reading and selectively editing a post to demonstrate an actual understanding of a concept. But in the lack of such understanding, such selective editing becomes the norm... over and over and over...rather than actually expanding upon concepts and adding to them. But such is the necessary limitation of a reporter and cheerleader and marketeer as opposed to one who actually understands the acoustical concepts and who can actually affect such behavior, rather than simply reading about it and posting marketing materials ...over and over and over.

This indeed is a classic case of why "it is so dangerous to go by tidbits of data on the Internet."

Polycylinders are scatterers as distinct from diffusors.
The distinction is most simply seen in terms of spatial and temporal behavioral characteristics.

Polycylinders affect only spatial scattering.
While true diffusors affect both spatial And temporal diffusion.

The fact is that few advocate the use of scattering or diffusion for the control of specifically mentioned "low frequencies" for very good practical reasons. The size of the scatterers or diffusors would be PROHIBITIVELY large for most practical applications!

BUT, if they WERE made large enough, diffusion can indeed be very effectively used to mitigate modal behavior.

Thus Ethan's example is an attempt to demonstrate the effects upon SPECULAR energy. The failure to understand this fundamental fact and context renders any claims of understanding as well as pronouncements about their low frequency modal behavior ludicrous as no such claims are even imagined let alone posited. If Ethan has made an error, it is in assuming that the audience has a greater understanding of the concept than is apparently the case.

And I dare say that more than a few understand this, although judging from remarks this fact may not be readily apparent or in evidence.

Thus the objection not only reflects a lack of understanding of the appropriate context for which such devices are used, but also of how they work.

Additionally, while a polycylinder is properly a "scatterer", they can be made into diffusors by using multiple units, whereby the scattered energy then superposes with that of other units to create a more complex well-mixed soundfield.

But one should also be aware that one must use multiple diameters in proper sequence to properly modulate the resultant power response.

Seeing that NO CLAIMS were made regarding their effectiveness at low modal frequencies, objections that "clustering them heavily damages their effectiveness in low frequencies. Yet no one would know that from your demonstration and negative talk about their performance" address a non-existent shortcoming. One might similarly suppose that single or clusters of the units are similarly not very affective at keeping your car clean or in seasoning stir fry.

Unfortunately, the problem exists only in the mind of those who are unaware of the much more fundamental limiting factors, namely that the units must be MUCH larger to have any significant effect on low modal frequencies (and if they are, they can indeed mitigate the modal issues! But I would suggest that units sufficiently large are not practical in all but an exceptional setting...). And one can hardly fault Ethan for assuming that a reader is not TOTALLY lacking of ANY and ALL conceptual understanding of the function or application for such units. The fact is, if Ethan is guilty of anything, it is in assuming that his intended audience is a bit more knowledgeable and aware than what is in evidence based upon the critical remarks above where diffusors are actively considered for use in resolving modal issues!

But hey, if it helps, it might be useful to similarly note that polycylinders are of little use in eliminating the need to mow your lawn on a routine basis as well. I hope that helps someone to avoid an unnecessary expense and disappointment if they were considering their use for such a purpose.

What WOULD be a welcome diversion for this forum would be posts that actually expand on folks acoustic understanding, rather than nit-picky selective edits that fail to enlarge people's understanding and which are directed only in one person's attempt to promulgate what is effectively a marketing campaign devoid of a necessary fundamental understanding of the subject, for which out of context cut and paste serves as a substitute.

But, I assume that we will continue to be assailed with limited out of context cut and paste editing complete with mis-represented assertions and equally mistaken conclusions based upon a fundamental lack of understanding of basic acoustics principles.

Prohibitive? Here are the measurements again:



As you see, the measurements for the single device shows its depth to be ~12 inches deep. The width is about 2 feet. This configuration provided useful absorption down to 200 Hz, making it a broadband device, which is the type we are looking for.

Is it something you want to stick on your living room wall? No. As I keep saying, you probably don't need anything there. If you are building a dedicated space and need a device as a diffusion, then it is a useful option given its performance above and a look that might better match your decor than other shapes (i.e. you can turn them into columns/posts).


That's right (even though Ethan does not at all address this point). In that regard, we need devices that are broadband and go down to transition frequency.

Throughout this thread, I though we were all in agreement that if you are going to use acoustic products for higher frequencies, we better have them work down to transition frequency of a few hundred hertz as to not shape the response of the speaker improperly. I recall Locahost asking repeatedly if anyone disagreed with that recommendation from Dr. Toole. I did not see you or Ethan raise your hand and advocate otherwise. So if we are in agreement there, why defend the use of this solution in a way that makes it non-broadband?

At some point you have to clarify your position Dragon. Earlier in the thread you said people should buy the $140 book on Diffusion and Accoustics from Cox and D'Antonio and not believe marketing brochures. Here, you are defending a marketing brochure with incorrect advice and comparison against data from D'Antonio.


A point that is made by Dr. Toole but not at all by Ethan:

"Figure 21.11 shows the normalized diffusion coefficient for a single and then for multiple hemicylinders with a 1 ft (0.3 m) diameter. Obviously, in isolation the device works very well, and in this thickness it is effective down to a usefully low frequency. However, when combined with others, it loses the ability to diffuse low frequencies. The geometric regularity is also visible in the cyclical pattern in the curve. The solution is obviously to space them, probably by random distances, and possibly to vary the depth."


My criticism is not at all related to whether anything is solving "modal issues." You seem to have confused my use of the term "low frequencies" with what exists below transition frequency. In my book, 300 Hz is "low frequency" so is in Dr. Toole's per above quote. If I wanted to talk about modal frequencies below that, I would have said so. But I didn't.


Putting aside your continued confusion about my point regarding low frequencies, that is why I said his videos are like chapter 4 of a book. The only way to know what he is showing is wrong is to know what you are trying to accomplish and why. And that is to diffuse some reflections (not all), and do so without damaging the response of a good speaker. To get there, you need to *first* discuss speakers and psychoacostics of sound in a room. Only after that is understood can you then look at these solutions. If you have that knowledge, and combine it with *data* on these devices, then you know if a solution is right or not. Jumping to a point where a bunch of cylinders is shown together and say, "look, it doesn't work so well" is not where it is at.

Again, it is clear you misunderstood the comment and then ran with it. Benefit of doubt is not given to your counterpart so assumptions are made and long posts ensue. But the goal is accomplished. We looked at "marketing material" by Ethan and showed that real data, from the authors of the $140 textbook you recommended, shows it to be misleading and incorrect. So at the end we accomplish something.

And after all is said and done, our time is wasted with an absurd digression about the use of polycylinders as if they are diffusors, listen to someone erroneously dismiss and fail to understand their use in an array, and utterly miss the fact that they effectively became a very limited use device with the advent and first measurement of the first actual Schroeder diffusors - ironically at the LEDE seminar in Dallas in 1983.

Yeah, its we who have actively used diffusors for 25 years who do not understand them...

Beware, as next we may be treated to a debate over the use of wire recordings...

Yawn.

From the $140 textbook by Cox and D'Antonio:

"Performance of simple curved diffusers

For normal incidnece, diffusers base on part of an arc of a cirlce have good dispersion performance."

From http://www.aes.org/e-lib/browse.cfm?elib=12121

Title: Two Decades of Sound Diffusor Design and Development, Part 2: Prediction, Measurement, and Characterization
Authors: D'Antonio, Peter; Cox, Trevor

"Semi-cylinder diffusor. This was made of oak, which was turned,
sawed, sanded, and finally waxed to fill the pores. " [shows a picture of a single semi-cylinder]

As to your time being wasted, I apologize. As I have said before, I am not writing for you.


So you are now doubting the validity of your own reference? Here is the graph again:


It is clear there is no redeeming value in using them in an array that way.


As I said, they provide something Schoreder type diffusers do not: a look that may be conducive to a home theater when you can't hide them. In real world, we want to solve customer problems and in that regard, these devices provide a very useful tool. The overall experience is important to achieve. I appreciate the larger picture may not be of value to you.


The people who have done that, were in the graphics I showed. And text that followed. They are not fighting forum fights but do this for a living and realize what to do, and what not to do. An example of the latter was in Ethan's video.

For anyone desiring solid information on poly scatterers versus actual diffusors, take a look at this paper, authored by Cox, co-author of Acoustic Absorbers and Diffusers.

And also note the comments regarding periodicity, modulation and period width.

Also, the issue of levels of absorption exceeding expected levels such as is mentioned in section 6 of the paper have since been identified, analyzed and accounted for in the form of "edge diffraction".

You see, some are not quite as confused as a result of loosely using the general term "diffusor" and failing to distinguish between the actual behaviors and their more appropriate description based upon actual behavior.

And if you want a technique that works that does not have the appearance of a Schroeder diffusor, you are better off avoiding the earlier confused 'analysis' and instead examining hybrid Binary Amplitude Diffusors (BAD) rather than poly scatterers.

 

Cox.AcousticDiffusers.GoodBad&Ugly.pdf 150.212890625k . file

In a home-sized room the reflected sound is more like 2 to 4 dB softer than the direct sound. If it was only 20 percent (-14 dB) the peaks and nulls would barely exist. That is, the peaks would be less than 2 dB and the nulls about 1.6 dB.

I never said absorption (or diffusion or deflection) at reflection points won't affect what you hear in a room. The graph below shows the response with and without absorption on one side. But your wording was imprecise by implying that sound passes through absorbers on the way to your ears.

--Ethan

Thank you, and this is why I asked (honestly) what the difference is between what Amir posts and what a typical forum troll posts out of boredom. I'm mostly retired, yet I don't have even 1/10th the time to spend posting as Amir apparently does. I truly don't understand what Amir objects to in these (many) threads, or why feels he must "correct" various "misinformation" he believes he sees. It's like, "Dude, exactly what is your point?"

And I'm still waiting to see waterfalls and/or RT60 plots of a typical home-size room that would not be improved by adding acoustic treatment.

--Ethan

Goosh Ethan!

According to the lesson we have just learned...more important than a reduction in the degree of comb filtering being reduced (ironically via an increase in comb filtering density!), such treatment must be flawed as it fails to correct for a 'less than ideal' frequency response of the direct source!



Its frustrating enough to have to spend so much time addressing 'urban acoustical myths' and well meaning but non-intuitive erroneous assumptions, but it is doubly frustrating to deal with some who like Paul on the road to Damascus 'hear' an account and suddenly via epiphany assume the role of self-appointed arbiter of all things acoustic as we have now learned that treatment is ineffective in that it does not address that which it was never properly alleged to correct, namely the quality of the direct signal.

Especially when the quality of the source and a controlled power response has always, by the major acousticians for the past 50+ years, been asserted to be a critical and fundamental component of the total speaker-room environment a fact only to have to be rediscovered by some who erroneously think that such a message is somehow new.

Its deja vu all over again...

But in the real world what wall is going to reflect the 20 to 20 KHz frequency back totally unaltered anyhow?

How about in an older home with thin wood construction that the lower frequencies can pass through relatively easy? Or single glazed windows that allows bass to pass through but reflects higher frequencies? Or any artwork/photos hanging on the wall? The frequency is going to be altered.

And who says everybody likes a flat frequency response as the ideal? Many people actually prefer a house curve over a flat response.

Quite often theoretical principal on a piece of paper doesn't directly relate to the dynamic and in-perfect real world.

You ignore time. Our brains are just a bit more sophisticated than that.

Thanks Ethan. I am relieved that despite skipping half the acoustics 101 class, I still get a passing grade. And on math too!

BTW, the sound does "pass through the absorbers." It is the reflected one that does that and hence the reason some of these products can damage the sound of a good speaker by reshaping its off-axis response. Just because you don't plug it in, it doesn't mean it is not an EQ!

And yes, I hear you. I am sure most people reading my original post, thought that diffusers and absorbers go in front of the speaker and not the wall . So thanks for clarifying that point.


Oh, the dreaded comb-filtering and magic of fixing of them with a first reflection absorber . Say, how come the response is down a whopping 18 db by just 11 Khz? What did it do by 20 Khz? Go negative? I know, I am again noticing gross distortions under the fine point you want to make there .

Well, I extend my apology to you for tiring your eyes with my posts Ethan. I am happy to answer your question since you honestly want to know.

Let's take the topic at hand, and your post specifically. You put up that graph above as to say, "look, you need one of my products. Don't you see it causes these peaks and valleys you want to fix?" I must say, it is quite clever. Unfortunately the science is not what it seems:

1. You show a microphone and what a computer is analyzing. You are asking us to examine it with our eyes, not ears. Same as what people do with expensive cables by the way .

2. If we look at what the ears hear, we have to start with the fact that two signals arrive. One for each ear. Why would you represent that with one microphone?

3. The right ear hears the reflections from the right wall directly. The left ear however, hears it after your head which is in the way filters it. Put your hands loosely on ears and notice how the sound becomes muffled. Same thing happens with your head in that some of the high frequencies are filtered. So spectrally the two ears are hearing very different signals. Again, this is not reflected on your single microphone measurement devoid of the effect of the head (so called Head-Related Transfer Function or HRTF).

4. Your ears are separated by some distance. So the combination of direct and reflection that the right ear hears, is NOT the same combination that the left ear hears. The reflection has farther to travel for the ear not facing the reflection. When you change the timing, the comb filtering changes since the phase of the indirect waveform changes and hence, the cancellation and additions occur differently. Again, your single microphone setup doesn’t show this at all.

5. There is not just one reflection in the room. The sound hits all the surfaces multiple times and keeps coming back. So in reality, we are talking about many signals summing and subtracting. This tends to fill in the valleys.

6. In real life, we hear these reflections all the time. We are indoors predominantly. The brain has an adaptive mechanism that lets it separate constant transformation that the room applies (if we are stationary) versus the dynamic changing nature of the content you play. It takes differing signals that arrive in each ear per above and sums them to a signal that is mostly devoid of the variations above. It performs non-intuitive things like giving more priority to faint reflections. Net, net, the brain has a very significant role here. There is no way you can expect the typical person reading a forum post or your graph to be aware of all of these factors and take them into account as they look at that graph.

7. If you are playing multi-channel music and movies, dialed in them is ambient information. Research shows that these cues overwhelm fair amount of room reflections. Indeed, our ability to hear artifacts in general goes down as the number of channels increases.

And it is not just me saying these things. Our virtual resident expert, Dr. Toole says it too:

” * In double-blind listening tests where listeners compare music with and without side-wall reflections, the results consistently indicate a preference for the reflections.

* Listeners given the opportunity to adjust the sound level of the reflection to maximize "preference" choose levels that are above the levels of the natural room reflections.

* BUT -- this relies on the speakers and wall surfaces that yield direct and reflected sounds that are similar in spectrum.”

He then says pros recording things tend to be more sensitive to reflections.

That aside, whatever negative attribute is left from comb filtering and side-reflections, there appears to be strong positives perceptually, none of which is evident from your graphs, web site, or forum posts. I think that is a problem worthy of discussion.

You are a man who always demands objective proof for audio claims. Yet, you put up that graph on your site to convince people this is a problem when proper science and double blind testing indicates otherwise.

Now it is OK for experts to disagree. It is our job then as readers to decide who has proven their case better. So if you don’t mind, it would be great in your next post to read the results of double blind tests you have run and published that point to efficacy of getting rid of side-reflections/comb-filtering. I also appreciate hearing how your knowledge of psychoacoustics supersedes the work of others above.

Please Ethan. Don’t go there . You post on countless forums. I only post on two and right now on AVS, this one thread only. Yes, I love to interact with like-minded people. I like to see my understanding challenged so that I can see if I can prove them (if not, then I don’t know them well enough and go back to study some more). What I don’t like to hear is another forum addict telling me he is more sober than me.

Please see above. And thanks in advance .


Can you please point to relevance of RT60 in our home listening environment? BTW, I did address the rest of that point the last time you asked that .

Its deja vu all over again! And the fundamental MISTAKE continues!

STILL he continues to confuse the role of early reflection control as distinct from control of the quality of the direct signal! A totally unrelated issue!

If you truly wonder why the direct signal rolls off, contact the speaker manufacturer and stop wasting our time demonstrating a profoundly fundamental misunderstanding of acoustics.



Rather than a post that explains and clarifies issues, we have yet another that arrives on the scene, full of all sorts of intent to correct and clarify, yet it lacks the awareness and knowledge of just what it is exactly they imagine themselves to be arbiter.

Instead what we get is half-formed notions based upon an incomplete reading of a book, where the only basis for comment is the imagined channeling of Toole, rather than the comments and understanding of one who actually knows whereof they speak or of whom actually has any experience or knowledge with actually studying and working with such analytical systems.

It truly grows tiresome where instead of addressing and expanding upon legitimate acoustic issues, that with each progression in the thread we instead are stuck pointing out the mangling and misrepresentation of concepts imagined to be new by someone heretofore ignorant of them and which have actually been around for quite some time. And which are trotted out in the form of out-of -context quotes presented only in an attempt to discredit others and to push one's new found religion based upon faith in a book, rather than upon any personal understanding of the subject matter.

In other words, its fine to post quotations from external sources if they serve to augment ones understanding and the point to be made, but not when they function as a substitute for one's fundamental lack of understanding of the topic.

And in that spirit maybe now would be a good time to re-post the same picture of 'the room' that folks are supposed to either literally copy of attempt to extrapolate intuitively to their room independently of any evaluation and consideration of the REAL power response of their speakers and/or of the room boundaries themselves... After all, all you need to really do is to become proficient in focusing upon the mantra "I believe..."

The fact is, if anyone here wants to read Toole, they can get a more pertinent and accurate interpretation by simply reading the book rather than being subjected to an arbitrary poorly functioning version of a Kindle.

You know what might be a better and more constructive idea? Seeing your design and measurements Dragon. You could then give us a tutorial on how it is superior to any other approach. I have asked for this a couple of times but saw no acknowledgement. I appreciate you helping us learn more by doing that. Thanks in advance. .

Sorry, no. The point was simple. A measurement with one microphone is not the same as two ears and a brain hearing it. Period.


There is no "room." There is no cookbook. You are being taught how to fish. Once there, you then know how to design your room while following the best research in science of speakers, room and psychoacoustics. That is how I am able to critique the ideas you are putting forward. While the teachings can be summarized, it doesn't fit your lingo of this room model, or that room model.


That's right. I hope people get the book. It is $44 and it is the best $44 you will ever spend. An even better bet is to spend the few hundred dollars and take Dr. Toole's two-day course at CEDIA in September. I assure you that you will learn more than you ever could here.


Sorry, no. I was explaining the mechanism and the mechanism is described by HRTF: http://en.wikipedia.org/wiki/Hrtf

"HRTF describes how a given sound wave input (parameterized as frequency and source location) is filtered by the diffraction and reflection properties of the head, pinna, and torso, before the sound reaches the transduction machinery of the eardrum and inner ear (see auditory system). Biologically, the source-location-specific prefiltering effects of these external structures aid in the neural determination of source location, particularly the determination of the source's elevation.[4]"


IACC is a measurement, not a description of the phenomena or the cause. From the paper, "INTERAURAL CROSS CORRELATION AND SPATIAL CORRELATION IN A SOUND FIELD REPRESENTED BY SPHERICAL HARMONICS"

"Spaciousness is an important psychoacoustic feature in room acoustics, with the interaural cross correlation (IACC) an accepted parameter for its measure, the latter employing the head head-related transfer functions (HRTF).....IACC is measured using a human or a dummy head and is computed from the time correlation between the two ears. IACC is affected by the head related impulse response (HRIR) or head related transfer function (HRTF) which are the time and frequency response functions between a source and the ears of a listener."

And Dr. Toole:

"The directional characteristics of our ears are described by “head-related transfer functions” (HRTFs; Blauert, 1996). These are complex (amplitude and phase versus frequency, or impulse response) descriptions of how sounds arriving from different angles are modified on the way to the eardrum. Because of the detailed structure Hearing: Human Listeners in Rooms
38 CHAPTER 3 Sound in Rooms—Matters of Perspective of our external ears and the placement of the ears on each side of an acoustically reflective head, HRTFs are unique characterizations of each of the incident angles of incoming sounds, helping us to localize where sounds come from."

We have explained the concept of acoustical response models selected in accordance to the site, purpose and desired preference as well as the various use of tools to determine actual behavior and the means to affect modification and to verify the effectiveness of such modifications in order to achieve whatever response your little heart desires.

The fundamental difference between us being that one of us has actively spent time specifically studying and researching physics and acoustics (with more than a few of the giants in the field) and have actively used these methods and measurement for over 25 years in both applied acoustics work as well as high tech optics and imaging research and development - rather than simply having finally gotten around to reading a book and experiencing an epiphany.

And if you desire still more, you might reference the posts attributed to "SAC", as you apparently are the only one here who still has not established the nexus despite your persistence in attributing the continuing erroneous connection between the superposition of direct and indirect signals as somehow having a causal connection to the nature of the direct signal itself.

HRTF is not an explanation of the differences between what is experienced between the two ears. It is an explanation of the physical behavior of the various signals that interact with the body that are subsequently then directed to the pinna and inner ear. There need not be any necessary difference between what is experienced per HRTF from ear to ear.

And inter-aural cross correlation (IACC) refers specifically to the degree of agreement or correlation between what one ear perceives and what the other ears perceives - which may or may NOT occur as a result of HRTF. The relationship is not a measurement per se but a relationship whose degree of agreement can be quantified. The coefficient that may be determined via measurement and given a value is simply the quantification of the relationship.

The irony is that you describe lateral reflections in your limited understanding of the process whereby your sole understanding is from quotes and references to Wikipedia. If you find that exciting, just think of the feeling if you actually tried measuring and evaluating such correspondence firsthand! Oh my!

So tell us, what do you know of Puddy Rodgers ground breaking research in the area of HRTF? Or of the extensive IACC studies done by D'Antonio and Ferrel Becker utilizing the ITE mics, both ~25+ years ago rendering your newly experienced epiphany 'old news'. And why doesn't Toole utilize the IACC measurement capability readily available in many measurement platforms in any of his posted measurements? Why? As the differences are minor in a symmetrical well-behaved listening space. And we also understand the relationship well and how it relates to physical measurements in a space.

Funny, but with your numerous flatland frequency response measurements, you never seem to feel it necessary or appropriate to post binaural measurements! If such measurements are necessarily so critical, how come YOU and your champion seldom if ever use them?????

In fact you have not thus far posted one such binaural measurement nor graph that reflects binaural measurements. NOT ONE!

Or are you the only one singularly exempt?

But since you now deride others for not posting binaural measurements, we will similarly dismiss any of your cut and paste postings that similarly lack binaural measurements, per your own stated lofty standards - of which ironically you have little first hand knowledge but about which you have only thus far read references and subsequently have become an authority via your recent epiphany qualifying you to now deride others.

And still your sole contribution as you continue to confuse the role of superpositionally imposed comb filtering as having some imagined relation to the unmodified quality of the direct signal is to cite the well understood issue of IACC which is rendered effectively moot in a symmetrical environment! Ironically for the same reason your idol used mono signals for his preference testing! But you still don't get it seeing as your 'understanding' is limited to quotes from a book.

But let's see, if the modification of a signal is effectively identical from 'both sides' of the two perceived signals that are effectively averaged, what is the net effect of the additional signal? Put very simplistically, it is 'cancelled' out as they used to say in elementary school math.

Thus in a controlled environment where one goes to great lengths to insure the unmodified spectral balance of such indirect signals and insures lateral symmetry, such differences become asymptotically of less and less significance as the differences decrease in nature and magnitude.

The fact is, like bandwidth limited ETCs, IACC is a great diagnostic tool that is able to provide additional diagnostic insight into some situations, but neither are fundamentally necessary for routine examination of acoustic behavior.

And for the most part we understand the nature of the optimal relationships and simply such in the form of generalizations such as the preference for laterally arriving reflections.

Well, let me rephrase that, those of us who ARE aware of such relationships are able to do that without the apoplectic histrionics of chastising others for not providing only binaural measurements where such are not necessary!

But by all means, run back and grab yet another quote and let it substitute for an understanding of the real significance of what is cited, as after all, why should one actually understand that which one is simply copying and pasting as a substitute for actual understanding.

Oh, and an acoustical response model is a 'map' or 'template' for the acoustical response of a room. Every space has one and every pro offered theory has one, whether they are aware of it or not. And Toole's space featuring spectrally balanced early and late reflections repeatedly alludes to one, although the silence is deafening regarding the presentation of an objective standard by which one can effectively and objectively adjust a room so as to meet the objective standards that correspond to a particular subjective psycho-acoustic response.

And go reference the RPG PDFs depicting the various acoustic room models as D'Antonio compares and contrasts the prominent acoustical response models as you persist in claiming Toole and his room do not have one. So now the appropriate response of the room is amorphous and unable to be defined. LOL!

Great! Now folks, go out and modify your space accordingly to a standard that has no characteristic acoustical response! Or wait, apparently only one who has drank the Kool-Aid can affect such a room FOR you (for a 'reasonable' fee), as the non-existent acoustical response model is possessed only by a true believer entrusted with 'the secret'.

Cue the marketing brochures....

Has the original question of this thread been answered to the satisfaction of the OP?

Clearly not as there are violent disagreements on any part of the answer we approach. If you think there is consensus about anything, it would be great to hear it .

Hi Chu. Who would you like to answer your question? And do you mean Audyssey or devices of that class?

So my direct q to skylinestar.

Do you have clear direction on how to proceed?
Or, are you confused by the answers/advice given?

That's the ubiquitous response of a Radio Shack SPL meter. That graph is from many years ago. I since bought a pro sound sound card with phantom power and a precision DPA microphone.

--Ethan

LOL, how dare you ask that!

You are so incredibly disingenuous. Expansive cables vendors never show how the audio changes when their product is used. The only "looking" is at the pretty colors and fancy gold plated connectors.


This is correct, and I've made that point many times. That's why the severe comb filtering, which really is present, doesn't sound as bad as it looks. The deep nulls at one ear are usually not as deep in the other, so your ears average the response. But - and this is a biggie - the gross difference in left-right response harms imaging. Badly.


I don't care what Floyd Toole says about this. He's right on a lot of stuff (most stuff), but in this case he's wrong. If he were to query more sophisticated listeners he'd find that reflections in a smallish room are always heard as damaging to the sound. Maybe in a room 30 feet wide those reflections could add "good" ambience. But not in a typical home sized room where the reflection are early.


RT60 should be uniform over as wide a range of frequencies as possible. Even if small rooms don't have truey reverb, RT60 is still the metric we use, and it's still a good way to measure.

--Ethan

Good question. I did a little searching and it appears that the OP last posted to this thread on 4/3/2012 (about a week ago!) and thanked all for their help.

After that the thread became yet another AVS dogmatic arm wrestling match.

Can someone please explain to me, what are diffusion panels and when/how should they be used in both a 2 channel setup as well as a home theater setup? Where do absorbion panels mostly need to be placed, (ie, first reflection points on the walls or ceiling) and where do diffusion panels need to be placed?

Of course I realize that every room is different, I am just looking for the basic and general places that would benefit most from room treatments.

You and/or the other guys can answer. I'm talking about a receiver or prepro that has Audyssey.