Comparison of small room acoustic models for home listening spaces - Page 6 - AVS Forum
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post #151 of 415 Old 02-24-2012, 06:16 AM
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Quote:
Originally Posted by localhost127 View Post

there IS NO appreciable reverberation in small acoustical spaces! why can't this misconception die?

I think reverb in SAS was about ready to die, but then you posted the link to the MyRoom diffusion/absorption hybrid project earlier in this thread:
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Originally Posted by localhost127 View Post

here's a model for a surround sound control room in a very constrained (small room) - utilizing LF absorption w/ HF diffusion.

http://www.bozoel.com/hosted/myroom-...hite_paper.pdf

They describe their process of achieving their room and how it performs, and page 7 is devoted to Reverberation Time.
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If we use the equation for the nominal value RT60 (Reverberation time), for the control room, we get (in our instance) 0.183s.

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post #152 of 415 Old 02-24-2012, 06:45 AM
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Originally Posted by kromkamp View Post

That's crap (like most of this conversation). Substitute the word reverberation for diffuse field (and ITD for ISD if you want to be pedantic which you surely do) and its precisely relevant for small rooms.

this is not an accurate statement. you still don't understand the terms.

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Originally Posted by kromkamp View Post

Most reasonable humans would grasp the nature of my query, and the fact you seem continually unable to speaks to your comprehension, not mine.

what query is this?
tell me, what questions on RFZ room model have you asked that have not been answered to the best of my ability?

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Originally Posted by kromkamp View Post

Anyways I'm done with this. I originally wanted to try to attempt to build one of these out, but quite frankly I can't imagine the enjoyment I might get from it would be balanced out by the soul crushing banality of having to talk to you for one more second.

you are not here to learn and explore. this much is obvious.
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post #153 of 415 Old 02-24-2012, 06:58 AM
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Quote:
Originally Posted by Eyleron View Post

I think reverb in SAS was about ready to die, but then you posted the link to the MyRoom diffusion/absorption hybrid project earlier in this thread
They describe their process of achieving their room and how it performs, and page 7 is devoted to Reverberation Time.

unlike you, i did not specifically call out and quote RT's from the paper and post them within the thread (as i know they are not relevant). the link was provided merely as example of another room design.

please, direct any "grammatical" or spelling errors within any pdf i link to as my fault as well.
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post #154 of 415 Old 02-24-2012, 08:27 AM
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I'd like to pick up again on this. For SACD/DVD-A MCH music, I use the ITU layout with five identical monopole speakers. Nearly every title I have is an in-the-band mix with usually only the basic trap set "anchored" to LCR with the corollary being that vocals and other instruments (including other percussion) can be coming from any of the five speakers. And they phantom image things between left surround and left front just like they do between any of the LCRs. Ditto between left and right surrounds.

For the same reasons that attenuating the first/early reflections from LCR is A Good Thing, would it not be appropriate (necessary?) to do so for left and right surrounds?

With Toole talking about dipole/bipole surrounds, I get the impression that he did not contemplate the scenario and content I just laid out.

Jeff

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Originally Posted by Eyleron View Post

Toole's book talks about this a bit in the surround speakers chapter.

It does suggest that front absorption would keep the surround speakers' sound from coming from the front. And that the considerations versus two-channel are different.

Toole also prefers bipoles over dipoles, because the latter can have a screwy FR and sacrifice localization when you want localization, whereas bipoles provide a good compromise.

22.3.1 Side-Wall Reflections from Front LCR Loudspeakers


In 22.3.3 re: surround channels and wall reflections, he says that in an anechoic chamber, five speakers were able to envelop one listener in sweet spot. But for more than one listener, one needs uniform dispersion over a huge horizontal angle, like +/- 90 degrees, which you get with certain speaker designs but not dipoles.

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post #155 of 415 Old 02-24-2012, 01:22 PM
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Quote:
Originally Posted by localhost127 View Post

unlike you, i did not specifically call out and quote RT's from the paper and post them within the thread (as i know they are not relevant). the link was provided merely as example of another room design.

please, direct any "grammatical" or spelling errors within any pdf i link to as my fault as well.

Well it was a little jibe at you, but only because you sounded so frustrated, which is funny when it's a term that's being used by Toole regarding small spaces, or the professionals building studios that you linked to, or Nyal here bridging the gap between "technically, scientifically, it doesn't apply to small rooms, but in practical use it has some value" (paraphrased) sort of statement.
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Originally Posted by Nyal View Post

Decay time is more widely termed reverberation time and is typically defined by the RT60″ measurement, or the time taken for the sound level to decay by 60 dB. From a purely scientific perspective the use of RT60 in small rooms is not valid since the science and reasoning is based on the assumption of a statistically diffuse soundfield, which is not a characteristic of a small room. From a practical perspective, however, RT60 is a good indicator of whether reverberation time is in the ballpark for high-quality sound reproduction.

Nyal also uses it here
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Now I am not familiar with any of Rives work personally but for a pure two channel room I am not sure why they would be targeting an RT60 of 0.2s. For a home theater maybe (but even then that is a dead room) but certainly not a two channel room. Anything below about 0.35s in my opinion is not good for two channel. I target 0.4s with a +/-25% error range for the frequency bands from 250Hz to 4kHz. The IEC even has published guidance on this - see the RT60 - reverberation time page on my website for a discussion of targets etc.

Interestingly, the "reverberation time page" he speaks of, although its URL is also "Reverberation-Time," its main heading on the page itself is "Decay Time" and he makes no further mention of reverberation time on the page.

Do you see the point? Acousticians and scientists use the term, loosely, to refer to decay time, even in small spaces.

If they use the term in this fashion, surely we can, too?
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post #156 of 415 Old 02-24-2012, 01:42 PM - Thread Starter
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Again I shake my head. I haven't quite understood the nature of some of these miscommunications that have occurred regarding these topics over the past few months. There is a lot of knowledge to be shared, and people seemingly interested in learning. Should promote a useful exchange but there are repeated misfirings.

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post #157 of 415 Old 02-24-2012, 01:56 PM
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Quote:
Originally Posted by Bigus View Post

Again I shake my head. I haven't quite understood the nature of some of these miscommunications that have occurred regarding these topics over the past few months. There is a lot of knowledge to be shared, and people seemingly interested in learning. Should promote a useful exchange but there are repeated misfirings.

The basic nature of some is to be didactic and contentious.
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post #158 of 415 Old 02-24-2012, 02:08 PM
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Quote:
Originally Posted by pepar View Post

With Toole talking about dipole/bipole surrounds, I get the impression that he did not contemplate the scenario and content I just laid out.

Actually, I vaguely recall some passages / caveats about multi-channel music that I skipped over.

I'll try to find them again.
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post #159 of 415 Old 02-24-2012, 02:15 PM
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Quote:
Originally Posted by Bigus View Post

Again I shake my head. I haven't quite understood the nature of some of these miscommunications that have occurred regarding these topics over the past few months.

Okay, since I already wrote in the master thread about interfacing with with experts and acousticians (making sure to qualify what your goal is, constraints are, etc.), I'll do my part and add to that to use scientifically correct terminology, such as "decay times" instead of reverberation times, since doing so is less likely to set them off and derail progress.

As a layperson I can try to do this, and I hope they try to stay more down-to-earth and pragmatic to work with us.
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post #160 of 415 Old 02-24-2012, 02:19 PM
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Quote:
Originally Posted by Eyleron View Post

Well it was a little jibe at you, but only because you sounded so frustrated, which is funny when it's a term that's being used by Toole regarding small spaces, or the professionals building studios that you linked to, or Nyal here bridging the gap between "technically, scientifically, it doesn't apply to small rooms, but in practical use it has some value" (paraphrased) sort of statement.

Toole isn't an acoustician - he is an electrical engineer who got into investigating and marketing room correction systems and speaker dispersion. if he was an acoustician, he would be using the terms appropriately.

and yes, "technically and scientifically" - reverberation ISN'T relevant to small acoustical spaces, unless you are a bat or a dog.

and Nyal realized his factually incorrect statement when i brought it to his attention. whether or not his documents are amended is not relevant to me.

http://www.avsforum.com/avs-vb/showt...8#post21475708

http://www.avsforum.com/avs-vb/showt...2#post21482582

and im sorry, but Nyal (as knowledgeable and helpful as he is) - is NOT an authoritative acoustician on reverberation as of those who actually developed the statistical equations and terminology many decades ago. his commentary or publications holds no relevancy with regards to the actual meaning of such vocabulary --- but he is free to speak for himself if he so chooses.

words have meaning in acoustics just as with any other topic. it is not my fault that "reverberation" has somehow been infested into the minds of every novice as to represent basic "specular decay". reverberation and reverberant sound-field have meanings. STATISTICAL meanings. they cannot be used interchangeably with simply room decay as they are entirely different behaviors.

you're simply looking for any excuse to make up for the fact that the default meaning that people have regarding the word "reverberation" is simply incorrect. are you here to argue or are you actually going to take a moment to understand what the actual definition of the terms are? anything BUT science forum.

acoustics differs dramatically based on the inherent presence of a statistical reverberant sound-field in LAS and local variable specular energy (magnitude/direction) in SAS. this is why we repeatedly have to instruct users to NOT emulate the "treatments" found in large theaters into their home theater, as the behavior is entirely different.



Quote:
Originally Posted by Eyleron View Post

Do you see the point? Acousticians and scientists use the term, loosely, to refer to decay time, even in small spaces.

If they use the term in this fashion, surely we can, too?

yes - you're utterly ignorant of the definitions of the words and how they are not interchangeable.

if you were here to learn, instead of make excuses to continue the use of acoustical vocabulary incorrectly (because hey - everyone else is doing it!) - then you may wish to read a mere 70+ pages from this book which will clearly outline the differences between LAS and SAS.
http://www.amazon.com/Sound-System-E...dp/0240808304/

but im sure you'll simply go on and look for other acoustical publications of which reference the word 'reverberation' in some futile attempt to make a point that loose and incorrect definitions of the terms are suddenly "acceptable"

although, it is quite laughable to watch you attempt to hold ME accountable for actually using the term appropriately, instead of those that are utterly clueless as to the meaning and the relevant volumes of space of which can actually support a reverberant sound-field.

and i also doubt you're even familiar with who Dr. Manfred Schroeder was, but hey - let's just go by what Toole states instead of the people who actually developed the knowledge on the very term...
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post #161 of 415 Old 02-24-2012, 02:35 PM
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I appreciate there are differences. I do know who Schroeder is.

I didn't mean that I'd use "decay time" to be interchangeable with "reverberation time," because I don't care to learn about the acoustics of large spaces (that I have been in), so I probably won't talk about it. And I've already acknowledge it's a scientifically different term. I meant that I'd use decay time instead of reverberation time when I mean decay time.

You asked the question, "why can't this misconception die?"

I've answered you with my opinion on why I think it doesn't die: these people who are doing things which aren't completely stupid are using the term in this incorrect sense. I'm not saying that you're wrong to not use the term, I'm showing you where it's coming from.

Maybe you should go to the root of the problem. Instead of stamping it out by neophytes like us, you should be going to these other sources, like you did Nyal. For instance, maybe the Audio Engineering Society should not accept papers for publication that misuse the term. I found several AES papers that refer to RT in small studios and cars.

I'm sure Kleenex and Xerox were similarly infuriated.
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post #162 of 415 Old 02-24-2012, 03:47 PM
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It's intermission time............take a deep breath..........relax...........

Close your eyes..........

I say this in all sincerity
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post #163 of 415 Old 02-24-2012, 08:12 PM - Thread Starter
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As often as the accusation is made that some people must not actually care about learning, it could be just as fairly presumed some do not actually care about teaching.

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I was sure hoping we would have acoustician localhost127s ETC, ETC, ETC, ETCs by now. You know, even one that he has done in his room. Actual in room measurements of his LEFZRED preference control room, using JBL wallmounts IIRC (polar response????). Where the mic was placed....and what it all meant perceptually...or preferentially.
Ah well....

cheers,

AJ
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post #165 of 415 Old 02-25-2012, 05:24 AM
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Quote:
Originally Posted by dragonfyr View Post

You know, it really gets old listening to 'social tweets' that instead of adding to any understanding of acoustics now hold the 'teacher', whose only job need be to present material, responsible for not learning the material for the 'student' as well.

So tell me, after how many years of being so intimately concerned with audio and acoustics and after all the time spent on this forum (in one case assuming just 1minute per post, a modest estimate of 350 HOURS simply posting!) as well as all the time spent reading marketing brochures, how much time has actually been spent reading any actual reference text about acoustics?

Obviously not much.

And dare one ask what is an "LEFZRED"????

As if you had bothered to just read chapter 6-9 of Sound System Engineering by Davis, 2nd edition - and yes, I specifically mention the 2nd edition as it has only been available since 1987 for all of you time constrained folks - covering:

Chapter 6 Loudspeaker Directivity and Coverage;
Chapter 7 The Acoustic Environment;
Chapter 8 Large Room Acoustics; and
Chapter 9 Small Room Acoustics;

not only would all of this 'controversy be moot, but you might actually have something productive to add regarding ACOUSTICS to the conversation.

Yeah, but the fact that others in the field reflect their ignorance and use terms incorrectly negates our obligation to understand and use concepts correctly! Nice argument! Let's see, and employing the same illogic to the fact that some folks eat dirt....

And the comments of a troll who feels that in order to communicate valid concepts that one need live in a facility. Gee, genius, I am qualified to discuss quantum electrodynamics, but the fact that I do not personally live in or possess a supercollider invalidates any concept one might have and validates ludicrous insights such as what you have posited...

This reminds me of an intro course in modern physics where a student who lacked even a firm grasp of classical physics proceeded to challenge the validity of quantum mechanics. But I guess, as the instructor lacked a supercollider, its necessarily invalid. As you see, its sufficient for someone who lacks any appreciable grasp of a subject to question an instructor based on the students oh so advanced grasp of the subject matter. ...And the teacher needs to "prove" it to them. Yeah, right.

Its not local's job to teach or to learn for you. He has been gracious enough to present material. Its YOUR job to expend the effort learn it. And while local is persisting in masochistically trying to present basic material to those who do little more than complain, I no longer care if you learn it or not as its rather apparent that the vast majority here lack the the desire to actually make an effort to learn (as evidenced by the ratio of posts to excuses for not having read such material) and the subsequent basic prerequisite acoustics knowledge to enter into an informed conversation as evidenced by a group not even aware of the fundamental distinction between large or small acoustical spaces!

For the record, I HAVE been in many of the facilities, and I HAVE both participated the many of the seminars and workshops both in and about them and made measurements in some of those facilities, and I do personally possess most of the source documents. And they are the result of folks with eminently more credentials than literally ANY other person who has ever posted on this forum. But yet we have pissants on this forum who lack an understanding of the most basic of concepts challenging the validity of measurements and data presented in both Davis' and D'Antonio's texts and publications!

The really amazing thing is that local persists in even trying to communicate concepts to a bunch of folks who claim to care so much about acoustics, but who have failed to even expend the miniscule amount of effort to read the most basic of resources available on the topic - and now they blame the 'teacher' for not learning the material for them. Waaaaaaaaaaaaaaaaaaaaaaaaa...

And considering that 3 of those denigrating local's efforts have literally in excess of 21,000, 3,000 and 4000 posts each!!!! 21,000 posts! Heck, if they only took a total of 1 minute each, that's over 350 HOURS or a half month non-stop! And yet they cannot be bothered to read the 75 pages that cover acoustical behavior in the various environments and Still lack the most basic information to enter into an informed discussion with local on these topics! Perhaps a better allocation of resources would be would be for some (some, heck, ALLOT) of that time spent talking to be spent reading, listening and learning; so that when they DO talk they have something of substance worth reading.

Yup, don't read the readily available resources for yourselves and then based upon understanding contribute constructively - instead play the victim and whine that the teacher did not learn the material for you!

What a genuinely pathetic mentality dominates the 'oh so interested' group of do nothing victims who can't be bothered to simply read and learn basic prerequisite facts sufficient to even engage in an informed discussion who instead offer nothing but denigration based squarely on their own ignorance as they demand "the answer".

not. one. single. in-accuracy.

it's ok, dragon - i always give them the benefit of the doubt and assume such behavior is merely due to poor quality control on the LSD in their area. nothing makes me more grumpy than crummy acid.
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post #166 of 415 Old 02-25-2012, 06:20 AM
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post #167 of 415 Old 02-26-2012, 04:10 PM
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Your questions got me re-focused on measuring my room. My situation is that I already have absorption at all first reflection points and I have been looking at replacing some of them/all of them with diffusion. It was basics that lead me to installing them in the first place, but verifying that they are working properly ... or whether it is a good idea to swap for diffusors, well I realize now that no one can tell me that or at least can't tell me that without measurements.

As you have reached this point, so have I; after I do the measurment(s), what does it mean? Well that lead me to the source of REW and these two threads. (I am still reading them.)

Starting at this post, this thread looks like a good place to start.

And then this thread on interpreting the results.

Back to reading ....

Jeff


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Originally Posted by kromkamp View Post

The only thing missing is an actual example that this achievable by an amateur with less than unlimited means.

Two more questions:

1)Regarding reflectors, it seems to me these would be much easier to deal with aesthetically than absorbers anyways - they don't need to be 8" thick to be broadband right? So what's the downside? Is it very difficult to place them for multiple seating areas?

2)What sort of treatment is appropriate (or not) for behind the speakers for RFZ?

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post #168 of 415 Old 02-26-2012, 05:25 PM - Thread Starter
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That sort of gets back to where I started this thread pepar. You can (and should) become as familiar as possible with both theory and practical implementation of various acoustic tools, methods, treatments etc. But your question sort of gets at the "but would it sound better" heart of the question. Even if you understand the process necessary to implement some room model as well as possible given your starting room constraints, there are still a few intriguing models to choose from. Aside from some generic associations such as "if you like more analytical perhaps x would be preferable, of if you like more utopic perhaps y" making that choice still seems an interesting and non-obvious one to me. And other than having been in the industry and having heard numerous implementations, going by the genetic associations, or just letting someone tell you what they think woikd be best, I haven't seen a lot of practical information about how to best approach this decision.

My intuition after reading some (certainly not all) of the primary texts and reading design rationale and results on both the blackbird studio c and wsr room is that a heavily diffused soundfield may be more appropriate for a dedicated multichannel system than one utilizing targeted absorption. But that's just my intuition. Short of building both in otherwise identical rooms, I'm still interested in thoughts on how to approach this problem.

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post #169 of 415 Old 02-26-2012, 07:09 PM
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As there is not agreement among acousticians, or EE's who stayed at a Holiday Inn last night, there may not be one right approach much less one perfect room.

Your comment about the heavily diffused soundfield is interesting. Somewhere in the last few days I stumbled upon a link to a someone's theater and except for bass traps in the corner, the room was full of diffusion. The comments on how it sounded were flattering. And then there is the design with an outer room that handles modal issues and an inner room with walls angled such that they deflect early reflections past the listeners .. kicks the can down the road as it were .. until it is, well "late" and part of the reverberant soundfield. I didn't dive deep into that design, but I'd guess that they deal with decay time on a "macro" basis.

I will post my "baseline" measurements ... in quotes because the absorbers are already in place ... and see if anything can be determined, iow correlated to how it sounds.

Jeff
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Quote:
Originally Posted by pepar View Post

My situation is that I already have absorption at all first reflection points and I have been looking at replacing some of them/all of them with diffusion.

Is that a function of the room, the acoustic sources you decided on/placement, or...?


Quote:
Originally Posted by pepar View Post

It was basics that lead me to installing them in the first place, but verifying that they are working properly ... or whether it is a good idea to swap for diffusors, well I realize now that no one can tell me that or at least can't tell me that without measurements.

What basics? Can't tell you what without what measurements? Does your perception of the sound play any role whatsoever?
Quote:
Originally Posted by pepar View Post

As you have reached this point, so have I; after I do the measurment(s), what does it mean?
Jeff

I was hoping at some point we would see some trace of description of the sound...and what goal it is you hope to achieve, based on it. Any idea?

cheers,

AJ
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post #171 of 415 Old 02-26-2012, 07:41 PM
 
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Quote:
Originally Posted by pepar View Post

As there is not agreement among acousticians, or EE's who stayed at a Holiday Inn last night, there may not be one right approach much less one perfect room.

Jeff

Over what sound they....and you should prefer? How could there be?

cheers,

AJ
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post #172 of 415 Old 02-26-2012, 08:17 PM - Thread Starter
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AJ, that's part of my question. How can I know which sound I prefer?

Granted, it's easy enough to locate high gain early reflections and properly absorb them, and do so in a manner whereby I can decide if I prefer the effect of absorption or not. However many of these room models under discussion are quite involved in with construction and treatment outfitted. It doesn't seem possible let alone practical to attempt any sort of AB comparison. Even if one took the absurd path of building out one room model, listening, then demolishing the room to build out another, the auditions would be widely separated temporally.

On the other hand, if I seek out rooms having implemented these various models, they are likely to be of differing sizes, filled with different equipment, and I would still face the nonideal reality of widely separated auditions. Short of having heard so many implementations of each that one might build up a lasting impression of the averaged behavior, I'm still stuck at that impasse whereby I can read all the available theory on these room models, know how to implement any one of them, and still be unsure of which I would ultimately favor. If the time and cost were in line with say swapping an avr or even a pair of speakers, that would be one thing. But we are talking about room constructions requiring significant investments of time and/or money.

So it isn't so much that no one can tell me what I would or should prefer but rather I'm not sure how to even decide for myself. This isn't a rhetorical question for me. I have been researching and refreshing my understanding of these issues as I approach construction of a new home that is still a couple of years away. I will have freedom to implement anything from bare walls to sprayed geometry to heavy diffusion. And yet there is nothing in my reading that solidly answers this quite primitive issue. I have a suspicion that I will ultimately have to combine all I've learned through reading and asking questions here with my rather limited auditioning of several rooms and simply make a best educated guess, never finding out if it was the optimum outcome.

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AJ, that's part of my question. How can I know which sound I prefer?

No idea. I can only tell me/you what I prefer, based on my perceptions.

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However many of these room models under discussion are quite involved in with construction and treatment outfitted. It doesn't seem possible let alone practical to attempt any sort of AB comparison. Even if one took the absurd path of building out one room model, listening, then demolishing the room to build out another, the auditions would be widely separated temporally.

On the other hand, if I seek out rooms having implemented these various models, they are likely to be of differing sizes, filled with different equipment, and I would still face the nonideal reality of widely separated auditions. Short of having heard so many implementations of each that one might build up a lasting impression of the averaged behavior, I'm still stuck at that impasse whereby I can read all the available theory on these room models, know how to implement any one of them, and still be unsure of which I would ultimately favor. If the time and cost were in line with say swapping an avr or even a pair of speakers, that would be one thing. But we are talking about room constructions requiring significant investments of time and/or money.

The problem (for me), is that while my perceptual system exhibits the "adaptation" Toole et al have found in their research, the "listen through" ability (despite the horrors one might "see" in a measurement), it operates at a subconscious level. Thus I do not (consciously or otherwise) have the "gating function" ability that others have, where I can eliminate (gate) the sound of the acoustic sources (creating the soundwaves) and "hear" the room. As such, when I vist an RFZ, or LEDE or whatever control room, I hear the source/my position/room, not "the room".
Others obviously have this skill. Probably the same folks that can go to an audio show, listen to the system and "hear" an amplifier or other individual component. Rather remarkable skill, this gated hearing thing.
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So it isn't so much that no one can tell me what I would or should prefer but rather I'm not sure how to even decide for myself. This isn't a rhetorical question for me. I have been researching and refreshing my understanding of these issues as I approach construction of a new home that is still a couple of years away. I will have freedom to implement anything from bare walls to sprayed geometry to heavy diffusion. And yet there is nothing in my reading that solidly answers this quite primitive issue. I have a suspicion that I will ultimately have to combine all I've learned through reading and asking questions here with my rather limited auditioning of several rooms and simply make a best educated guess, never finding out if it was the optimum outcome.

I don't have that problem, since my 2ch preferences are laid bare with my products and recommended placement/"treatment" of room...and for HT, nobody in the audience, including me, has yet complained about the sound (usually the contrary).
Which is the question always sorely missing from the "I'm going to pad my cell" threads. What's wrong with the sound??

cheers,

AJ
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post #174 of 415 Old 02-26-2012, 08:59 PM - Thread Starter
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Rather remarkable skill, this gated hearing thing.

Agreed. This again is part of my stated difficulty. I have no delusion of being able to visit two different rooms on two different days with different speakers, of different sizes, likely at different volumes etc and isolate the contributions of room model a vs model b. So how do you really know which model you prefer?

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from bare walls to sprayed geometry...

Gotta love phone autocorrection.

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It doesn't seem possible let alone practical to attempt any sort of AB comparison.

Not for us consumers/hobbyists, but companies can use binaural room scans to instantly A-B different systems/rooms.

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post #177 of 415 Old 02-27-2012, 07:11 AM
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AJ, that's part of my question. How can I know which sound I prefer?

page 6 and we're still stuck on the "sound" of a room? what ???

the goal of the listed acoustical models is to preserve the accuracy of the direct signal. non time-aligned high-gain indirect signals are going to superpose with the direct signal at the listening position for frequency-response anomalies (comb-filter interference pattern). you can quite visibly see this when you take your "ruler-flat" speakers and place them into a bounded space. however, the frequency-response gives you zero information regarding the ACTUAL high-gain indirect signals (and their incident boundary) of which is the result of such superposition.

high-gain indirect signal mgmt is the basis for psycho-acoustics (how those indirect signals arrive with respect to time of the direct signal). there is no "sound" to these models. it's merely to preserve the accuracy of the signal emitted from the source without the room applying its own transfer-function to the response at the listening position. where is the confusion in this ?

a Non-Environment Room (NER) is a completely damped room (speaker-listener response) such that the direct signal is the only signal that is processed. the signal is completely accurate as there is no difference between output signal at the speaker and input signal received at the listening position. the room does not modify the response at the listening position. accuracy is preserved. there is no "pleasing" attributes applied to modify the response at the listening position based on user preferences. that is not the goal in such a scenario and implementation of such room model.

LEDE/RFZ manage the indirect specular signals such that the direct signal is the only signal processed within the haas interval (such that no other high-gain indirect signals are fused with the direct signal), preserving localization, imaging, and intelligibility. unlike a completely damped/dead room, specular energy is eventually re-introduced back to the listening position (termination of effectively anechoic ISD-gap), to give a sense of spaciousness to the room --- along with the psycho-acoustics of a haas trigger and the density of the diffused returns (vs sparse reflections bouncing around the room maintaining their location, magnitude, and vector/direction components). this is why the response varies so greatly within different locations or seating placements within the room in the specular region. this is a fundamental issue of being within a small acoustical space vs the statistical equal energy flows of a larger acoustical space.

control rooms are critical listening environments. the room needs to be as neutral as possible such that mixing/mastering decisions are accurate and the room is not imposing its sound on the direct signal (and thus, mixing decisions - garbage in garbage out). eg, if the transfer-function of the room causes a -30dB null at 80hz - you're going to boost 80hz to compensate. now, when you take the mix to another room, 80hz is going to be way too loud in gain and the mix will suffer. the goal is to preserve accuracy of the signal and to remove the room from decision making process. while such effort is not a requirement for a home critical listening room, the same acoustical responses can be applied if one so chooses (eg, the purpose of this thread).

Bigus,
you're already creating the effectively anechoic ISD-gap of which high-gain (early) indirect signals are attenuated (in your case, via broadband absorption) - of which will flatten the specular frequency response due to reduction of superposition of high-gain indirect signals, and increase intelligibility, localization, and imaging. the high-gain indirect early signals need to be attenuated below the human detection threshold (thus, why we only focus on HIGH-GAIN and not ALL reflections that are low gain). you can attenuate the signal via redirection, absorption, or diffusion - but as discussed with those who wish to use "thin" absorbers - whatever choice you choose needs to be effective throughout the entire specular region down to lower Schroeder cut-off frequency - otherwise you are merely coloring/filtering the reflection. this is also dependent upon the polar response of your speakers and acoustical impedance of your boundaries, which is why measurements (vs a mirror) are crucial.

however, that is just one step in the complementary "package" of such room responses. it is not difficult to create a damped room! that is the problem we see all too often and why "surgical" application of broadband absorption is required (and why redirection is preferred) - vs blindly applying absorption on boundaries of which a high-gain indirect signal may not even be incident! eg, measure and identify issues before applying 'treatment'. the difficultly of achieving such responses is to maintain and manage the specular energy in the room appropriately, such that it can be re-introduced to the listening position at a later time. the gain and the time-arrival of the termination in LEDE/RFZ models is not casual - it is required to induce a haas trigger. and it is also not easy to achieve - especially if one is relying on broadband absorption to create the assigned ISD-gap length.
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the funny part is - even the flatlanders that are stuck in the frequency-domain (and ignore the relevancy of the time-domain) are clueless that constructive/destructive interference patterns (comb-filtering) as viewed via the frequency response are addressed and resolved with regards to the time-domain!
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Bigus - you don't have to make it soo complicated. Consider this - listening music in a big 'lively' normally furnished room, if you have speakers with good polar response, is an enjoyable exercise. (no high gain early reflections due to distances, modal problems start at a comparatively low frequency, etc) Everyone here agrees to this point I hope. Now scale down the listening space - as in a small HT, no normal furnishing, and you have couple problems. Modal activity and high gain early reflections and high gain periodic reflections(flutter). If you treat this room according to the LEDE blueprint, you get back the spacious sensation of your big room. You can make the returns lower in level to vary the sensation until the room is 'dead'. Thats it, no mystery, headache, decision etc.
Music is mostly produced to be enjoyed in a lively listening room. Movies are mixed in a space that has less 'spaciousness'. If you like to experiment, then invest in a room with variable acoustics. Removable absorbers/reflectors, covering a diffuser makes it an effective absorber etc.
You can also buy a http://smyth-research.com/technology.html and visit a couple great studios - fellow forum members have just done that.
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Bigus - you don't have to make it soo complicated. Consider this - listening music in a big 'lively' normally furnished room, if you have speakers with good polar response, is an enjoyable exercise. (no high gain early reflections due to distances, modal problems start at a comparatively low frequency, etc) Everyone here agrees to this point I hope. Now scale down the listening space - as in a small HT, no normal furnishing, and you have couple problems. Modal activity and high gain early reflections and high gain periodic reflections(flutter). If you treat this room according to the LEDE blueprint, you get back the spacious sensation of your big room. You can make the returns lower in level to vary the sensation until the room is 'dead'. Thats it, no mystery, headache, decision etc.

liveliness of the room is determined by the first significant reflection's gain with respect to the direct signal.

how the energy decays (sparse vs diffused, dense diffused, etc) dictates spaciousness of the room.

and speaker design/dispersion is integral to the room models as well! something many here wish to ignore. the room model's are not solely dictated by the specular response as achieved within the ETC - there are a host of other 'factors' as well that have not been discussed.

the goal is giving the brain ample time to digest the direct signal. something that naturally occurs in larger spaces.


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Music is mostly produced to be enjoyed in a lively listening room. Movies are mixed in a space that has less 'spaciousness'. If you like to experiment, then invest in a room with variable acoustics. Removable absorbers/reflectors, covering a diffuser makes it an effective absorber etc.
You can also buy a http://smyth-research.com/technology.html and visit a couple great studios - fellow forum members have just done that.

yes, and the detail of the recording room (eg, concert hall) is already inherently present within the source material (direct signal) as well! it is funny to hear people think that their "small room liveliness or spaciousness" is actually ADDING to the recording room's sound as present within the direct signal. removing the listening room's mask allows one to more easily hear the recording room present on the source.

it goes back to the blindfold test. blindfold yourself and go into a bathroom and speak or just listen to the ambient noises...now go into a larger room. the brain perceives the acoustical size of the room based on the gain of the indirect signals and their time-arrival within the time-domain.

hell, go and listen to a recording from a concert hall in your bathroom (of which the brain will easily perceive itself as being in a small acoustical room by nature of the arrival times of the indirect signals) - you will NOT be immersed into being "in" the concert hall. go listen into a much larger room where the indirect signals naturally arrive much later in time and at lower gain, and you will be able to hear the room in the recording much easier without your small room masking its presence on top.

it doesn't matter - so many people discussing "adding diffusers" yet i still have yet to see anyone even begin construction. why not build and experiment? i built my first early primitive root diffusers on casters with 4" OC703 on the backside such that i could easily turn the gobo around and switch between reflection phase grating diffusion and then broadband absorption. people can talk and talk for ages about "what if" ... or they could actually get busy and experiment.
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