Acoustic treatment for my living room - Page 7

Thanks Chu. I will wait to see if someone else likes to comment first.

Well, if you screw up with a power cable, about the worse thing that happens is that you lose money out of your pocket. Very likely your audio system will continue to work as it did before. If you screw up with acoustic products, you also lose money but also degrade the sound of your system.

And it is not like acoustic solutions are not sold on looks. How many people are not buying with their eyes that these things have to do some good, as opposed to how well they actually do that? They see pictures of these things in pro audio world of recording venues and automatically assume goodness.

Why do we put down our guard here Ethan? Or worse yet, are demanded that we do so? Why shouldn't we be skeptical about claims of audio improvements with acoustic products and ask for proper double blind tests demonstrating efficacy? Is there something here that automatically make their purveyors honest brokers and their products effctive? Let's look at this statement from the nice paper from professor Cox that Dragon post:

"ACOUSTIC DIFFUSERS: THE GOOD, THE BAD AND THE
UGLY"

“The ********** is a high-performance quadratic residue diffuser that employs a series of 15 wells of specific depths to break up and scatter acoustic energy.” A quadratic residue design must be based on a prime number, otherwise it is no better than a diffuser based on the lowest factors, in this case 3 an 5. Even stranger, the picture of the diffuser on the web site shows it to have 16 wells!

I searched for that product and is is still on sale and precisely as he says with that quote! So there is "bad" out there yet we sit here pretending it must be all good since it treats the room. Why? Why do we not demand objective data and listening tests to prove efficacy?

You and Arny are the two most vocal advocates of double blind testing. Yet, it seems that I am the only one who cares about that in this context. Why is that Ethan? I just did a quick search on your site and found no mention of any double blind testing of your solution against competing ones. Is it there and I missed it or is sighted evaluation based on a picture of the product good enough? I am supposed to look at rough measurements with a curve that looks nothing like a flat line and assume all goodness? Or posses the knowledge of Professor Cox to know that QRD style diffuser is built incorrectly?

You and I earlier agreed that acoustic products can color the sound of the speaker we hear. Surely since each one works differently in this regard, then we better do a listening test to see what is preferred. No?

Won't we be able to cut through all of these arguments if we had that kind of unbiased data? Yes, that data does exist in the literature but folks are quick to dismiss that here as marketing brochures (!) and instead like to convince based on how much they insist they are right. Isn't the guy who bought an aftermarket power cord just as insistent? We cut through that by asking for a listening test that shows efficacy. Yet, even the people who believe in such testing the most, don't practice it here.

You asked why I act like a "troll." Am I a troll for asking for data to show that these devices really work and do no harm? What is "incredibly disingenuous" is calling me a troll just because I question if the goods are really there, especially when top experts in the industry say it isn't.

The above statement reminds me of what I'd expect to hear typical science-means-nothing, margins-mean-everything audio dealer.

In fact if you spend a dime on a so-called upgraded power cable, you've lost a dime. Of course, no known high end dealer or manufacturer is selling his so-called upgraded power cable for a dime or even a dollar. Generally hundreds of dollars are involved, and its all a gigantic waste of naive customer money.


To be completely accurate, no matter what you do with snake oil like so-called upgraded power cables your audio system will continue exactly and precisely work as it did before. Snake oil is like that!



If we follow this logic then we must abandon any system upgrade that has the potential to audibly change the sound of an audio system. That is because anything that can make a positive audibly change is more than likely to have the potential to cause a negative change.

I've long suspected that from a dealer standpoint, snake oil is the better product, because he gets the money, and the client can't hurt anything with it. Thanks for confirming that, Amir!


Following this logic equipment has to hurt our eyes when we look at it, or else Amir is going to accuse us of selling out for looks.


No guard has been put down Amir - but thanks for showing us your true feelings in this matter.


Amir, given your past inability do do DBTs of your own on the gear you hype on AVS and/or sell in your little store, and your unbelievable statements about not needing to worry about level matching, the above is completely disingenuous.

< shaking head>

Who is that Arny? My company sells no power cords. Here is the list of our brands: http://www.madronadigital.com/Products/Products.html. And oh, thanks for turning a blind eye toward Ethan selling acoustic products though .


And that is all I lose. I don't have wall acne as I would with an acoustic product which may be degrading my audio performance to boot. It is like the worst of all worlds, having reduced fidelity and an upset wife complaining about the decor .

Really, do you think people want to put things on their walls? No one does. A power cord sits behind the equipment rack and on the floor. Can I put acoustic products there? Seems not. So we are asked to both spend money and mess with our rooms. You better have darn good justification for that and not just an opinion expressed on a forum as to why I should go and convince my family members I have a need to do that.


We make custom cables all the time for our installs from generic wiring we buy. Yes we charge for our time to terminate them but that goes with the territory in custom jobs. So your supposition there is uninformed.


What is the word for worse that snake oil? Because that is what we need to use for an acoustic product that makes my wall ugly, reduces my audio performance, required me to spend weeks here to learn what to buy and cost me money.


So we buy things on "potential?" Not on objective data?


Anything? Can you compare a good amp and one less than that and tell me how the good amp has the potential for negative change? And if it did, why I would buy it?


Well, thanks for confirming that all of this talk about double blind test this, and ABX that is just that, talk. When it comes right down to it, I am the lone voice of validity of objective evaluation. Folks call AES papers marketing brochures and Arny is outraged with me, not the person saying that.


Whatever Arny.


I rely on equipment designed by people who believe in double blind testing. And scientific research into what measurements and design lead to better outcome there. That is why we carry their solutions. They do the work so that I don't have to do it. When you get in the business, and remember the value of double blind testing, you can conduct all of your own tests when you pick products .

Do I have objective data all the time? Of course not. Folks like you want to give people a free pass so that they don't have to do it. Well, that is not OK by me. I am going to keep asking for such data especially when the person arguing is going against such credible research saying otherwise.

You want to shake your head, shake it someone calling double blind testing a "survey."

The above must be in error because I see no suppliers of wiring products on your web site's list - by which I mean the generic wiring and connectors that are needed to make custom wiring.

So, your web site is either incomplete, or you don't actually sell what you claim. Myself, my best guess is that your web site is incomplete.

We don't list screws we use on the racks either. Maybe you are right and we use duct tape instead to keep them there. Come to think of it, we don't list duct tape either on our web site. I must fix that or I will get accused of lying about that too!


No one is in need of your guess Arny. What we need is for you to be an advocate of objective evaluation of audio technology. Somehow you think this misdirection is where it is at instead.

Everybody who does a significant amount of installation work (like me) knows that there's a big difference in terms of billing for things like premises wiring as opposed to things like duct tape.

Amir, I guess this is your way of saying that you don't do much work like this or are either pretty much out of the details of what you call "your business", or that you have something to hide.

Amir, your posts here are a study in fight from reality. Doing a DBT related to room treatments is very difficult because of the physical scale of the changes that are involved. OTOH, you have for months been avoiding doing DBTs realted to say, jitter which are among the easiest tests there are to do.

While there is a controversy of the audibility of the kinds of jitter you have been ranting and raving about for months, the audibility of frequency response variations and echo suppression such as are obtained with room treatments is not controversial.

So there you go, Amir. I advocate testing things that are easy which you flee from, and you rant and rave about the lack of DBTs that are so difficult as to be practically impossible to execute.

If anybody has the resources to do DBTs of room treatments, it would have to be Harman.

Do not denigrate duct tape. To do so is unamerican. It must be given the deference it so rightfully deserves

you guys talk about "room treatments" here like it is a product in itself - like cables, dac, amp, etc- instead of the term being treated (no pun) as a "modification" to the acoustical space (room) to address a specific, measured issue based on the criteria chosen by the owner or room designer. it imparts an impression that there is a fundamental lack of understanding of acoustics and what such 'treatments' are attempting to resolve. this is most evident in the continued discussion of "reflections" - without so much as any understanding of the different types of reflections and which may or may not be destructive. it's funny that a user of this thread has attempted to say in the past that i myself have a "cookbook to kill all reflections" - and then has been unable to quote me to back up his claims. and as i use and continue to use descriptive words like "high-gain", "sparse", "early-arriving" to specifically and explicitly define the types of "reflections" im discussing (eg, the context), he simply called those "buzz words". no wonder acoustics is not a hot topic of discussion on this "audio theory" forum. we still have difficulties and confusion with such a simple topic as that of superposition...

a "room treatment" could be a high prime primitive root diffuser that has a varying depth up to 3ft, a thick porous absorber, or it could be as simple as a flat piece of wood angled to redirect specular energy away from the listening position. simple modifications to the room to alter the response (time-domain | frequency-domain) as identified by measuring the ACTUAL acoustical response of the room at the listening position(s).

Fight from reality is a nice froydian slip . The fixtures do exist. I have seen them and they are not difficult to build at all. Yes, it requires motors/hydraulics to move things behind a curtain but readily doable. As long as someone has done and easily so, there is no excuse but laziness and escape from the truth that it holds.

Sure, if you are an individual not in the business then it is fine to say you don't have the means to conduct such tests. But if you are a person in the industry like Ethan then this is something you need to do if you are going to say there are improvements relative to the products you offer for sale. Even if it were hard, it is not our jobs as customers to make it easy for you. Either you follow the research or you show objective data saying otherwise.

By the way, there are a number of ways to simulate these things that don't involve anything physical. One of the common ways is to use an anechoic chamber and then use one or more speakers that represent the reflections. Under electronic control you can change what the secondary speakers play and with it, what the reflections will be in a real room. To test a first reflection for example, you put a speaker at that imaginary wall position and then feed the same signal that is going to the main speaker but delayed and or transformed to the one representing the reflection. The switch over is instant then.

And it is not just double blind data that is lacking but also objective measurements. Dragon says he has been doing this work for 25 years. During all that time, he couldn't be bothered to make one measurement to post here? Or one double blind test? Has he toured Harman facility and can tell us why it is impossible to build such fixtures? Has he reviewed countless tests documented in the literature using the techniques I mentioned above? Have you?

Please leave the misdirection for others Arny. This is an acoustic topic. I am asking for objective data to back people's claims that are contrary to *published* research and double blind tests. And you are making excuses in post after post as to why not. As I showed from the quote of professor Cox white paper, people are indeed selling diffusers which cannot work as a matter of math. You show no outrage regarding that. You show no outrage that people call double blind tests surveys. You show no outrage that AES papers are called marketing brochures. As a guy who advocates these things all the time, it makes for a poor showing.


Oh they most definitely are. What do you think the arguments have been about in this thread? One guy says comb filtering is bad, and a top expert in the industry says it isn't. One guy says to use time domain analysis and the top industry expert says it is a waste of time. Let's put me aside. Here in an interaction from the first page of this thread:

Immediate answer:

You say there is a priority and he says it isn't. Which is it? Clearly there is substantial disagreement here and not over tiny things. The whole notion of how we approach this topic is hugely disputed. Dr. Toole says typical living room doesn't need treatment. Ethan violently disagrees if a picture of any listening room is shown without acoustic products. I would say there is more dispute here than any other audio topic I have seen. Just a page ago someone asked where to put diffusers and absorbers. You want to bet no matter who answers there will be an argument and a bitter one at that?

How do we get past disagreements like this in audio? We ask for measurements, explanation of science and double blind testing. Then we triangulate and decide what is right in our mind. I have looked the camps here and the only one that provides all of this is Dr. Toole and Harman group. The others throw stuff out there and say, there, it is a problem. When I ask them to show it, they get personal. And you chime in of all people defending them that they shouldn't provide these things? I mean where is one measurement that these posters have done themselves? I must have asked Dragon and Localhost half a dozen times and nothing comes forward. Yet you are arguing with me and not them.

Let's look at this example:

You are telling me this is not controversial? If so, why does Ethan have graphs on his site and full videos saying side-wall reflections create comb-filtering that should be cured with acoustic panels? Why doesn't the video say the opposite, that double blind tests show preference here despite the ugliness of the measurement?


I am advocating easy ones here too. Put a curtain in front of your side wall, have a person stand behind it and move a panel in and out of place while you vote on whether it does something good or not. How hard is that? But sure, if it is hard, then rely on others who have done the work for you as I do. Don't disagree and then complain that it is hard. If a car company crash tested two cars and found theirs to do better your answer can't be that they are wrong but it is too hard for you to do the same test.

And it is not just a matter of double blind tests. It seems that I am the only one talking about whether a distortion is perceptually audible. Everyone else wants to put forward a microphone and a graph to prove their case. No talk of perceptual effects. When I quote industry experts in this area, they call people who listen to them a cult. See Dragon's statement here: http://www.avsforum.com/avs-vb/showt...#post21865114: "Ah, the cult of Toole. So quaint and so limited. A cult? Limited because we dare to believe a comprehensive thesis?

Here is the type of teaching Dragon says we should not care about: http://www.avsforum.com/avs-vb/showt...6#post21834576


I could swear your position on measurements was that we should not care if we can't prove they are audible. Yet any discussion of that is dismissed and folks want to insist they are right to look at a single microphone and a graph representing the audible distortion. Well, it doesn't work for me. But it is surprising that it does for you.


You mean if anyone cared to correlate audible effects with measurements it would be Harman. People assemble large factories building automated systems to fabricate speakers or acoustic products (seem to recall CNC machinery in Ethan's shop). Yet somehow don't know how to rotate something physical in and out of place behind a curtain to learn more about what we hear???

My deepest apologies to Mr. Duct Tape and his extended family for the hardship I have brought to them with my words.

I see no published research that says that acoustic treatments of the kind that have been discussed here have no audible effects.

I am unaware of any double blind tests that says that acoustic treatments of the kind that have been discussed here have no audible effects.

Got any?

Motors/hydraulics to shuffle speakers or install / take away acoustic treatments?

What about DBT that's easier to carry out than speakers or acoustic treatments but not done such as DAC vs another DAC or HDMI vs S/PDIF? Would it be beyond "laziness and escape from the truth that it holds"?

this is exactly the type of commentary i just wrote about: the vague use of the term "reflections". as if their gain, time arrival, sparse/dense, spectral content, etc are completely irrelevant. you cannot discuss "reflections" without the context of the reflections. if only there were some "buzz-words" we could utilize to give context to the type of "reflections" being discussed...

and if only there was some measuring tool that we could utilize to identify how specular energy impedes the listening position based on the actual acoustical behavior of the space, the speaker off-axis polar response, acoustical impedance of boundary, time-arrival, gain of reflection, etc ... hmm...



by the way, does anyone know if i can send photos of my "typical living room" to toole so that HE (the living room expert) can make the decision on whether mine is "typical" enough such that i "dont need treatments", or whether my living room is not properly furnished and is more of a bare shell and thus requires "treatments" - based on photos alone? what are his criteria for determining whether my typical living room is more of a bare shell/room, or a sufficiently furnished living room. how many bookshelves do i need? how many chairs/couches? where should the bookshelves and chairs be optimally placed? what happens if my typical living room does not allow me to move furniture to the optimal acoustic placements? where is he drawing the line here? does he recommend any measuring tools i can utilize to measure the ACTUAL acoustical behavior of the space and make decisions upon that?

Wow. And as is so typical, not one acoustical concept is discussed. Its all about the tyranny of a subjective survey of selected listeners.

The same attempts to bludgeon others into accepting the one-size-fits all mindset advocating a paradigm that is neither universal in preference or application, as well as an ill formed process for actually achieving an acoustic response that is lacking any available systematic objective performance metrics enabling one to actively evaluate a space and to objectively determine compliance except for a few graphs of generalized perception levels which are little more than restatements or slight modifications of those long available.

All of that as one attempts to posit Toole's approach as the paradigm, when even Toole admits that it is simply but one approach preferred by some, but neither optimal or even appropriate for various other purposes including 2channel versus surround or critical listening versus 'big' fuzzy special FX...

The irony is that we have earlier attempted to present the means as well as some of the various major acoustical response models that are generally suitable for quite a few applications. And they are not the only options. And one can then, depending upon their application and preference, use the tools to hopefully achieve the response characteristic the desire that best elicits the acoustical response they desire.

The irony is that what Toole proposes is NOT new. And the concerns he worries about such as spectral imbalance are valid but old news as well, wherein much of the the rest of the industry was already aware of the issues and was glad to see him validate the concepts for himself.

But his PREFERENCE is only ONE possible response. It is one where the early arriving soundfield sacrifices accuracy and precise imaging for large fuzzy imaging that, yes, some people prefer. It adds nothing to the later laterally arriving diffuse soundfield that was well developed 30 years ago.

What is different is that someone here has recently discovered the concepts, and has failed to understand the context from which they emerged, and being largely ignorant of the progression of research and alternative models designed for various applications and preferences (as well as the actual concepts involved) now attempts to elevate this variant to the status of the ONLY valid model.

I personally have no problem with what Toole advocates as far as it goes. I personally prefer a more accurate imaging augmented by a diffuse sense of spaciousness and envelopment. It suits me for both critical listening professional use, 2 channel as well as surround, and for casual listening.

I am also quite capable of helping others to understand and to optimally achieve various other acoustic response models and everything in between by virtue that I not only understand the various response components that constitute each, but also a myriad ways in which they can be creatively achieved.

(Ironically, seasoned professionals have opted against exactly such a surround environment on steroids at Blackbird Studio C as the front and side diffusors have been draped with packing blankets rendering them absorbers in order to tighter the image while still providing a later arriving diffuse sense of envelopment and spaciousness. But hey, what do they know?)

But this flies in the face of someone who only accepts one model and who, by virtue of some subjective listening tests attempts to impose the tyranny of a few who regardless of context and use now attempts to force everyone else, whatever their purpose or preference to submit to a few who like big spectacular fuzzy imaging.

We get it. You like it. Unfortunately, short of simply cutting and pasting, you display little actual knowledge of the acoustical concepts at play, and even less understanding of many of the tools and myriad processes by which such responses can be achieved (oh, I know, just give you some time to go find a paragraph someone else wrote to quote...). Unfortunately, there has been almost NO actual discussion of concepts or addressing specifics, simply as one party cannot offer this. Instead what is substituted is the cheerleading of one particular point of view that assumes 'ideal' power responses - but which is severely constrained when one must deal with 'real' speakers featuring anything less, aside from quotes denigrating such use - which ALL have known about long before Toole even began his professional career!

Hell, that concept of uniform power response and controlled dispersion was a pre-requisite cornerstone for Don Davis and Tom Hidley as well - long before Toole arrived! Just as was uniform power response truly diffuse diffusors before they actually existed as well!) And as a result of the lack of the existence of such transducers, they advocated real world controlled Q devises whose power response over the available dispersive range was uniform.

And all while simultaneously advocating the same use of broadband treatment to mitigate boundary anomalies resulting from adverse high gain reflections, all Toole offers is denigration of practical treatments used to re-mediate exactly such REAL problems resulting from the use of REAL existing speakers from the period, as he, in hindsight, decries the lack of use of then non-existent ideal uniform power response speakers!

Wow, now that takes guts and knowledge! Especially as it also ignores the fact that the response model he attacks for not using his technique was also optimized for 2 channel and not surround! Ooops...
Gee, I wonder why he has also not chastised Edison's testing filament materials lacking the efficiency and longevity for not using technology that is only now available! So tell us, what speaker had an 'ideal' uniform 180 degree power response in 1977? (Hint, the Heil AMT configuration was 'close'...) So let's see the cut an past machine go to work now!

Prefer whatever you want.

But it takes a bit more insight and knowledge to understand the fundamental concepts at play, and to understand how various response models can similarly be preferred by many for a multitude of differing applications. And it takes a bit more to be able to evaluate various applications in conjunction with the PREFERENCE of the person who is paying for the design and realization of such an environment so as to achieve a final result whose performance satisfies THEIR desired preference than it does to simply tell everyone that one size fits all - regardless of the application and desires of the person whose preference is paramount.

The topic was not about acoustics but justification by Arny of people not doing double blind tests. Yes, such tests are subjective. But they are not "surveys." We are not asking people if they are republican or democrats. We put them behind a curtain, removing their personal bias, and ask them which sounds better. That is not a survey. Maybe Arny would be so kind to explain the difference between a survey and double blind test if you still deny such a simple scientific concept.


No one said it was. Dr. Toole gives extensive credit to others whose experiments and data he quotes. What he does do though is piece it all together in a comprehensive manner such that it is relatively easy to follow and highly convincing. That is pretty unique. Why else would you and Local constantly quote him just the same?


It is not *his* preference but that of countless listeners. He has an opinion formed from such data that he backs with 500 pages of writing. There is a big difference between that and a preference.


Then please stop complaining when I quote the man.


Yet, despite repeated requests, no objective data is presented by you in accomplishing any of this. Nothing. You won't even acknowledge the question let alone answer it. Why should we follow your writings in absence of any back up like that Dragon?


You are welcome to make your case Dragon. I am very open to hearing it. Just please don't do it solely by insisting that you are right over and over again. And with so many personal remarks rather than the discussion of the topic. Provide some data and let us discuss it. We can start with your own listening room which I trust embodies the best of what you are advocating.


I appreciate your angst in this manner Dragon. I honestly do. But I hope you also appreciate that I am not writing for you. It matters not that you are upset and unhappy. What matters is that you put forward your own data that disputes what I have presented. And for some reason you don't feel that is necessary to do so.


By all means, let's address the specifics. I have showed you measurements of our room. And we discussed them. It is your turn now. Please put them forward.


If you have known them then we are done and in agreement. Yet, the complaining goes on....


We are screwed if this is all about preferences like food is. That means there is no wisdom to follow. We better not ask anymore what to do about room acoustics if everyone prefers what they prefer.

Thankfully, that is not what double blind tests of expert and ordinary listeners tell us. They provide a shared preference that can be our compass to better audio and the direction we need to go. You can choose a lone course into the Forrest if you like. Just don't ask us to follow you when there are marked roads created by others .

There is nothing vague about "side-wall reflections." That is specific and precisely to the point of what type of reflections is being talked about.


Then please put forward data that shows relevance from psychoacoustics point of view. Lest you want to advocate that we listen with our eyes on a graph than with our ears.


The context was clearly given: side-wall reflections. No buzzwords. No sonar charts with ETC and such. Simply, easy to understand statement that listeners like side-wall reflections.


The measuring tool you need is a perceptual one. One that models the human ear and two ears. A microphone and an ETC graph I am afraid is not that or even remotely so. And talk about "buzz-words" thrown around....


No photos. He tells you to measure the RT60 and if it is within certain range, then you are good to go. This by the way, comes from research by others who have performed such surveys. From AES paper:

Title: A New Reference Listening Room For Consumer, Professional and Automotive Audio Research
Author: Sean E. Olive1
Harman International


"The reference setup produced the lowest
average RT60 value of 0.4 s. It is interesting to note that
the diffusers actually reduced the reverberation time,
probably by their scattering of sound towards absorptive
surfaces. For the reference setup, the 0.4 s value puts the
reference room’s reverberation time among the typical
values Bradley measured in 600 domestic rooms [10]."


You don't know? And you keep arguing? Do you not own his book you quote from? Have you read the above paper?


Well, now you know .

amirm, how would you put on and take off acoustic treatments in a room with motors / hydraulics for DBT? I'm asking you since you have "seen them and they are not difficult to build at all."

quoted for preservation of ignorance of acoustics and psycho-acoustics.

but if time-arrival and gain of the indirect reflections are so irrelevant, and we can just lump all specular energy into the vague term "reflections", then what is this image saying?




funny that - as the "perceptual ear-brain" has ZERO capability or resolution as to determine discrete signals arriving within the haas interval.

and the ETC is also especially useful to determine edge or cabinet diffraction as well - but you probably don't have any concern with speaker edge diffraction, do you?

hmm, and what measurement tool fits into the image above of "gain vs time"...hmm,


don't care - rt60 is NOT relevant in small acoustical spaces. not sure why you keep propagating this paper. if reverberant sound-field exists at frequencies we are concerned with in typical living rooms, thus validating the use of rt60, then maybe you wouldn't mind taking a measurement of your space past Dc? hint - you won't be able to.

remember, just measure "rt60" like toole says, and as long as you're "within a certain range", you're "good to go". nice deflection as he NOR toole is able to answer the question. just deflect and point to a "rt60 time". but what if my "typical living room" does NOT have a "rt60" time that meets toole's criteria? does that mean i have to modify the space in order to achieve such a "rt60" time? or is the room doomed for all eternity...

keep posting - and ill keep preserving the ignorance by utilizing the quote feature. you simple do NOT have even a basic understanding of acoustics. you are NOT able to actually provide ANY of your own commentary or opinions as how to better the acoustical environment for sake of music reproduction - especially in the context of if one wishes to have an accurate, critical listening space by which the masking of the room is minimized. your only recommendation that you continually propagate is that if one has a "typical living room", then "no treatments are required" - and this is apparently backed by a copy-paste from toole.

You are right that RT60 is not relevant to figuring out what to do with your small space in the specific. But for a gross measure of whether your room fits the criteria that you asked about, it does serve that purpose.

You need to have that argument with Ethan:

My use of it in answering your question was very different. I suggest reading the papers to appreciate the distinction.


Sorry, I assumed that you have Dr. Tool's book and can read the details. Here is a specific quote:

"In home entertainment rooms the requirements are quite simple: keep the
reverberation time below about 0.5 second so that speech intelligibility is not
degraded, but don't let it get too low or the room sounds abnormal."

As you see, it is a general metric meant to categorize but not treat.


Thanks for the commentary . If you can put aside your emotions and ask specific questions, I will answer.

thank you.

diffusers REDUCE the "reverberation time" due to the fact that diffusers in themselves are absorbers. edge diffraction and viscous 1/4wave resonance losses.

i would hope that one would not expect diffusers to "add life" into a room - unless what they are being replaced with is even more lossy...

Let's say you want to test whether an absorber on the side wall is effective. You build a wall. On one side you hang your panel, on the other, you leave it blank. Mount that wall on a central shaft on a motor with stop indicators at 180 degree point. When you need to switch, then you power the motor and rotate the wall until the stop switch is hit and then stop. Put a curtain in front of it and subject wouldn't know which is which.

Another concept is the RPG Triffusor. These are triangles with a different treatment on each side that rotates on a shaft. Would be trivial to motorize the action. This works pretty closely to how Harman reference room utilizes to test different wall-mount speakers. They place them on each side of the panel and then rotate it on demand using PC software.

Hydraulics could be used to shift panels in and out. Harman uses this technique to shuffle stand-alone speakers in and out of the same location behind a curtain (theirs is a 2-axis movement). Same method can be used to slide a wall back and forth with one part having treatment and the other not.

Watch factory floor automation and you see many examples of these.

I think I saw that in an old Abbot and Costello movie.

When trying to compare treated vs untreated room, what will you do about changing resonance and low frequency absorption due to that panel mounted on the wall even when facing the other side?


What will you do about the seams around the moving elements? What will it cost to select and assemble these hardware?


LOL!




Not so simple once you start to think about it, is it, amirm?

That's what you thought...

how about some education whilst we are at it.

could someone explain 'how to use' the graph (post 200 from local) please?

ta

Building rapid-changeover mechanisms like that is common on robotic automobile production lines. My sources who are familiar with building this kind of machine tell me that for a few million dollars each, they will build you as many as you would like.

Got any funding for this dream project of yours, Amir?

I found an online example:

http://www.youtube.com/watch?v=QvPKFDinhHU

Thanks Arny. I suspect if he said $1M you gave him the wrong description of the project. Here is a picture of the rotating version as documented in their AES presentation:



I am confident building a three-sided segment like this and a motor to rotate it is not even remotely in the $1M range. Please show the above to your contact and get a second estimate.

As I mentioned, you used to actually be able to buy the above triangle style units from RPG that let you easily experiment with diffusion, absorption and reflection. Here is a sample image I found of them:

We had them on the walls of our audio test room at Microsoft. Alas, they were not broadband so we didn't use them much. Ours was manual in that you rotated them by hand but motorizing a shaft with stop indicators is not hard or expensive at all.


You know, I have wished we had it at our showroom. I think it would come quite handy in convincing people that there are for example in-wall speakers that sound superb. But show them the little speaker in a drywall and they just don't want to believe that a ton of science went into making them sound good.