Determining Optimum Room Dimensions for Critical Listening

[dragonfyr]

Attached please find an excellent article from Peter D'Antonio & T. Cox that will help those who ask the ever popular question: What are the optimal dimensions for a listening room.....

roomsizerDimensions.pdf

[IndyKlipschFan]

I would agree with a lot of what was said. Thanks a good article. I would also point out what we all know too that different speakers require certain placements. ( K horns especially.)

There is very much a science and a little bit of luck in the art side to match perfect equipment and speakers and of course source material too.

I think the scientist group looks only at laws and forgets, for instance, if you deadened everything in a room without any reflections the speakers would play wonderfully what they are designed to do..yes.. but the unlifelike experience especially for live music might make you nuts and unfulfilling too. (Think of a HT in a Anechoic Chamber for instance.)

All speakers have some sort of "colorization." A lot of the design and the components determine this. Some speakers have a unique sound all to themselves too. This is not necessarliy a bad thing. We tend to like sounds that are pleasing to our ears and may not be so pleasing to some one elses.

Artto has great experience in this area for Music playing through Klipsch and how to incorporate a terrific room too. He might be the first to also tell you he did not design it for HT, and to do so, would require a different approach too. (I think he also said he hates HT but anyhow...)

Of course we all can learn a lot from the laws of science of what works based on certain parameters and incorporate those to our benefit too. I am certainly also trying to do so in my own design of a HT/ Karaoke room. Size wise, based on formulas that have been givin in here, I should be fine. Now if I get lucky and the match of the equipment and the speakers and source material all come together, I will be very much a happy man.

[dragonfyr]

{NOTE: Just a few selected ideas taken OUT OF CONTEXT and quoted for reference. This is NOT meant as a disagreement nor a debate with the Author, but rather I simply edited a few comments to use in addressing a broader issue! OK!?}

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I think the scientist group looks only at laws and forgets, for instance, if you deadened everything in a room without any reflections the speakers would play wonderfully what they are designed to do. Yes, but the unlifelike experience especially for live music might make you nuts and unfulfilling too. (Think of a HT in a Anechoic Chamber for instance.)

All speakers have some sort of " colorization. " A lot of the design and the components determine this. Some speakers have a unique sound all to themselves too. This is not necessarily a bad thing. We tend to like sounds that are pleasing to our ears and may not be so pleasing to some one else.

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Just an observation and a plea if I might I have selectively edited a few phrases out of context, not to disagree with the last comment, but to make a more general observation.

A primary issue that we seem to commonly face on this forum is an assumption that they, you know, that amorphous scientific group whom no one ever identifies, is out of touch with acoustics. Yet there is often asserted some equally amorphous they who have some esoteric feel for acoustics that enables them to outwit the bumbling technicians.

Many posts refer to the problems with science and to the art of acoustics.

To the degree that some may present limited models oversimplifying and inaccurately incorporating variables present in the real world and thus deviating from the complexities of reality, I will agree that science may be 'limited'. But this 'art' to which one refers would correlate only with one's ability to compensate for the limitations of a model with some 'stuff' that causes their resultant model to more closely correlate with reality.

I have read references to Many models which are treated as current that are grossly outdated, or have been greatly modified through repetitive listening correlation studies. A prime example of this is the LEDE/RFZ model. I dare say few know of its current applied form (and it most certainly is NOT to eliminate all reflections as I have read in numerous places!) And most objections I have read refer to iterations of the model that are 30 years old! And while basic premises are ageless, 30 years is an eternity in the modern evolution of acoustics.

Another example of an often venerated idea that has lapsed from favor is the use of simple diffusion using the cylindrical wall treatments that Paul suggested. While the basis was sound, the correlation with listening tests suggests a more evolved model. Does that make the idea wrong, as with those bumbling scientists? Of course not! And to suggest that he ignored reality is such a gross oversimplification as to be laughable! No more so then one would laugh at Einstein as many of his ideas have since been modified or eclipsed in the realm of quantum physics!

( I will post another two additional articles by Peter DAntonio regarding the use of diffusion as well as an article regarding distortion in Home theaters as an introduction to some of the current thinking regarding these issues.)

Yet I am not sure, as many are NOT familiar with the most current models, to what science they refer. And herein lies much of the problem with trying to have a coherent discussion in the forum. That which is attempted to be discussed tends to too often remain amorphous and a constantly moving target. We are positing vague assertions and even more vague responses without adequately defining the constraints that define the nature of the issue at hand. And just because someone has some meter does not make them and their solution current more accurate. In fact, I would assert that using instruments without an exhaustive understanding of the underlying physics has led to Far too many gross abominations in the field! And the RTA (followed by the EQ!) is perhaps responsible for far more then any other instrument! Indeed, while they do have their legitimate uses, just a small amount of overly reductionist information is indeed a dangerous thing! Nevertheless, such abuses do not negate the correct use of tools to address well defined issues.

So in this regard, it would be nice for the critics of the scientific models to specify exactly what model and what specific aspect with which they disagree, so that a coherent discussion might ensue.

For instance, disagreeing with the LEDE model is not sufficient! Which iteration? What specific aspect, and what specific attributeas each of these models deals in quantifiable attributes and not feelings or stuff.

Is this fair? For instance, when there are discussions regarding crossovers, stuff are not generally discussed. Each of the response characteristics can be quantified given the proper instrumentation and each are well understood. Just as qualities such as tightening up the bass, etc., is an easily quantified quality! And very well understood!

The purpose of a well defined acoustical listening space is to accurately facilitate the accurate reproduction of the source material, adding or subtracting nothing in the process. A well designed room makes no attempt to compensate for speaker 'coloration' (a term that to me seems very similar to my technical term "stuff"). It is speaker neutral. In fact it cannot correct for a poorly designed speaker, and attempts to do so will only create additional anomalies. If the speakers are flawed, you will hear the flawed performance.

Additionally, a well designed room is not designed without regards to a source. In fact, a poorly designed speaker can definitely add to the issues to be overcome in an acoustical space!

In fact it is the tuning of the INTERACTION of the speaker with the room that is the ultimate goal.

I keep hearing many refer to the problems with science and to the art of acoustics.

To the degree that some may present limited models deviating from the complexities of reality, I will agree that science may be 'limited'. But this 'art' to which you refer would correlate only with one's ability to compensate for the limitations of a model with some 'stuff' that causes their resultant model to more closely correlate with reality.

Yet I am not sure, as many are NOT familiar with the most current models, just what science they refer to. Just because someone has some meter does not make them and their solution current nor accurate. So on this regards, it would be nice for the critics of the scientific models to specify just what model and what specific aspect they disagree with so that a coherent discussion might ensue.

But simply to dismiss acousticians as those who look at "laws" (what laws?) and design anechoic chambers for home theaters is irresponsible. Or, to grant credence to the assumption, Anyone who would do this is an unabashed idiot and is not a reputable acoustician!

I wonder at the supposition that the scientist group looks only at laws and forgets, for instance, (that) if you deadened everything in a room without any reflections the speakers would play wonderfully what they are designed to do. Do they? I have never heard an acoustician, even one with whom I disagree completely, suggest this! Perhaps an acoustician whose goal is noise control might, but I have never even heard any of these folks make such a blanket assertion! And I have NEVER heard a reputable acoustician look at an issue as a one dimensional problem, without being well aware of the complex nature of myriad relational degrees. Context is by its very nature the awareness of an element within complex interrelated and interactive system.

So while it is easy to group the @#%$ scientists into a group of bumbling nabobs who have no concept regarding what they are studying, I dare say those acousticians who are worth their paycheck are far ahead of the models held on the forum, and dismissing them carte blanche simply displays a gross ignorance.

And it is exactly in these areas that there are some exception forums for sharing the cutting edge ideas and evolution of acoustical thinking and modeling. And this area is currently evolving MUCH faster then any other area of audio, due in Large measure to the fundamental research of Dick Heyser and the ability to quantify phenomena via tools such as time delay spectrometry!

So please, rather then the all too common Luddite response to modern acoustics, might I suggest a more forward orientation to the discipline. And a greater focus on discovering what the cutting edge of acoustic thinking presents, and how it presents valid tools for use, instead of resorting to a level worshipping esoteric practitioners possessed of some black art!

Ironically, it is in the area of acoustical analysis and design that the real advancements are presently occurring in the area of audio!

(And yes (anticipating the seemingly inevitable But what about.), there are some questionable current theories as well as products! But it is not within the scope here to label any of them. And as much as I might find fault with them, they are each entitled to a rational analysis of their relative strengths and weaknesses! The last thing that is needed is another overly simplistic witch hunt as has occurred with Bose and Monster, which regardless of their documented weaknesses, have so many here simply parroting abuse without having an informed clue as to the basis of that which they say!)

So its just a thought, as rational discussion of some of the newer and current ideas have much to offer. So an understanding of their various assets (and limitations!) would be of benefit to all.

[dragonfyr]

P. D'Antonio article1

Min RmDistortionInHmTheaters.pdf

[dragonfyr]

P. D'Antonio article2

TechBullDiffCritList.pdf

[dragonfyr]

Take a look. I hope there is something there that might, depending upon your background... as we have so many from SO many diverse backgrounds here!, that they might stimulate a bit of thinking.

Enjoy...

[michael hurd]

Thank you for posting those documents! There is a lot of information in there to digest. Some points that I have noted: the listener can be too close to a diffusor, leading to abberations, or anomalies in the scattered sound. Cylindrical or curved surfaces will return a lot less energy to the source than a simple diffusor such as evenly spaced wood battens.

I will definately reread these, and have saved them to my ever-growing cache of information on all aspects of audio.

[DrWho]

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On 4/19/2005 10:39:36 PM dragonfyr wrote:

The purpose of a well defined acoustical listening space is to accurately facilitate the accurate reproduction of the source material, adding or subtracting nothing in the process.

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I think it's in this statement that the "art" aspect comes into play. Let's say we have an acoustically perfect room with perfect speakers and perfect amplification and perfect source material...we now get to hear exactly what has been recorded. However, that puts us in the hands of the mixer and his own personal tastes. I dare say that 90% of the time I don't want to hear what the mixer did because it just sounds bad. Allow me to use myself as an example: I've got 13 years of mixing under my belt (I just turned 21) and I've got access to two studios, each with tens of thousands of dollars of recording equipment. I've made my fair share of recordings and I dare say that the majority of them sound better when I'm listening at home, than when I'm in the studio. My listening situation at home is very far from ideal. Granted, I must confess there are times when it sounds worse at home too. But if the goal was to make it sound exactly as it did in the studio, then I suppose it's a bad thing that it sounds better to me at home. Heck, there are times when an mp3 sounds better than the original 192kHz recording!

When it really comes down to it, I don't think any of us really want to hear exactly what has been recorded. The ability to pick and choose different sonic signatures (whether it be the source, speakers, amplification, or the room) is what makes the hobby interesting. Besides, the ideal could never be accomplished anyway which means even with the best of science, you are forced to pick your compromises (aka, sonic signatures).

This concept spills over into mic techniques as well, but let's not go there.

[dragonfyr]

Yes, in an ideal acoustic environment, you are ultimately limited by both the artistic and the technical capabilities of each step of the creative process regarding the the quality, techniques, and various resources employed in the creation of the source material...not to mention the quality of the media itself!

And unfortunately, what you ultimately hear is not necessarily a good thing!

But occasionally you are surprised by the combination of truely amazing skill and technique!

(one such example of this is Animal Logic 2 - a superbly recorded work of those 'unknowns' Stewart Copeland and Stanley Clarke, et. al. Seldom have a superbly tuned drum kit and mixture of electric and acoustic bass sounded SO good!)

[Zen Traveler]

dragonfyr,

Thanks for posting all of this technical stuff. I am downloading and printing trying to get a grasp of what is important in my situation. Unfortunately I am not a very technical person when it comes to numbers, but I try my best at trying to understand the concepts without doing the math

I read the "Brief History of Time," 3 times slowly, still didn't understand it -- Watched the video countless times, barely understood it--got the CD ROM, learned just enough to convince myself that I got the concept and felt comfortable with my spiritual beliefs.

I absolutely love my Home Theater and can't really change things too drastically because of space limitations--I hope I don't start to understand the literature downloaded and find out what I've been enjoying sounds like crap.

Please post when a video or CD ROM is available in case the written word doesn't sink in.

[dragonfyr]

I wouldn't let it bother you THAT much! Especially if you have enjoyed it! The point isn't to cause distress, but to facilitate optimizing your enjoyment!

And quite frankly, if you or a friend/child, etc. has a school ID, I would suggest getting a educational copy of MatLab, Mathematica, etc. to do the math modelling. It will let you do the what if value selection and it will do the obtuse number crunching and graphing for you!

And as far as the general physics is involved, check out the "Elegant Universe" by Brian Greene - on DVD! An excellent intro to TOE (the Theory of Everything (or Grand Unification Theorem) and an intro to string theory) if you want a great intro to the current discussion unifying 'macro' and quantum physics. But by all means AVOID the companion book unless you are a true glutton for punishment (or unless you want an introduction to the math that physics grad students are employed to deal with; aka "slave labor"!). And they wonder why the physics folk walk about mumbling to themselves! Here's your answer!

[colterphoto1]

that made my brain hurt!

Michael

[IndyKlipschFan]

may I also suggest the DVD movie:

"What the bleep do we know"

I have seen it 3 times now. I laughed, and got a lot out of it too.

The purpose of a well defined acoustical listening space is to accurately facilitate the accurate reproduction of the source material, adding or subtracting nothing in the process.

True.

A well designed room makes no attempt to compensate for speaker 'coloration' (a term that to me seems very similar to my technical term "stuff"). It is speaker neutral.

Thats the idea behind most great HT rooms too.

In fact, it cannot correct for a poorly designed speaker, and attempts to do so will only create additional anomalies. If the speakers are flawed, you will hear the flawed performance.

Also true. crap in = crap out.

But sometimes what is one mans crap, is another mans favorite meal!! Well, maybe not.. hahahaha

[dragonfyr]

How else would one explain rap? The music for those who can't do music...

[IndyKlipschFan]

Dr Who said, "When it really comes down to it, I don't think any of us really want to hear exactly what has been recorded."

LOL, I agree here too.

Think how many vocals have a "signature sound" we know instantly who he or she is singing within 1/2 a second. LOL. Great producers keep those tricks "hidden" and singers as musicians want to have that signature sound that way over their careers.

Funny thing is sometimes it is a mixture of a dry vocal track with some major tweaking (Effects) that just gives it a very unusual sound that everyone else tries to duplicate.

I can't imagine say Paul McCartney without that classic "Wings" sound or Sting, Rod Stewart, Phillip Bailey, Geddy Lee, Josh Groban, Frank Sinatra, Celine Dion, Shania Twain, Britney Spears, Christina Auguilera, Rob Thomas, Luther Vandross, John Mellencamp etc., EVER being who they are without it too.

Personally, I always use two effects signals to the speakers for me singing in stereo too. A straight dry signal and a digital delayed one. I sometimes use other minor tricks too. (I do not use pitch correction and or vocal harmonizers or machines to "dirty it up" like most of today's screamer bands..LOL) But critically listening "Just to the vocals" is interesting if you have never done that before. Maybe, just maybe, I could at last figure out just what Bob Dylan is singing anyway ..LOL. OK, Maybe NOT!!

[dragonfyr]

I am going to simply assume that we address two completely different, and equally valid, aspects of the creative/re-creative process.

On the creative side, we have the choice of either accurately recording the actual event without massaging it, or as engineer you can become part of the creative process by transforming the recorded event into a derivative product (Stevie Nicks or Brooks & Dunn comes to mind here...as the Ultra-Harmonizers go into search mode!).

I have no issue with this. The engineer indeed has the option of trying to create any desired effect that might be at their disposal or ability to create, and my own feeling is that sometimes it is is quite amazing, and too often, quite necessary, given the talent they are charged with 'capturing'... or in some cases 'searching for and chasing down'

But, that aside, my point was more to the issue that once this process is complete. And once that material is mastered, that process is concluded.

At this point it becomes the 'audio system's' responsibility, as I see it, to accurately reproduce that which has been recorded and transferred to the media as a final product. At this point, it is not the system's job to attmpt to redefine or contribute to the creative process of the engineer/artist. It is simply to acurately reproduce that which was 'created' in that total process. And to, as much as is possible (and I have no fantasies regarding the challenge that this 'simple task' entails!), to provide reproduction of that event analogous to the proverbial amplifier model that has been stated as 'a straight wire with gain'.

At this point we are freely able to render our opinion of the job the artists and engineers (from recording to mastering to pressing) have done, be it wonderfully amazing or simply 'amazing'(sic).

Thus I do not see it as the listeners' responsibility to attempt to re-engineer the mix nor to pretend to be able to fix any aspect of that process. (Unless of course individual tracks are provided for exactly this purpose such as artist's like Peter Gabriel have at times provided). And even in that exceptional circumstance where an attempt is consciously made to redefine the role of the listener, it is still the responsibility of the system to reproduce those tracks 'accurately' and to render them ready for any post processing one may want to do. and to transparently reproduce the processed signal accrately. But I do not accept that role as primary, except insofar as the challenge is to accurately reproduce that which has been recorded.

Just as a transfer function is a measure of the difference between input and output, my measure of a successful sound reproduction system is for it to extend that analogy to account for the electro-mechanical-acoustical (and one might easily add pyschoacoustical) interfaces and to accurately reproduce that which was recorded in the form it was recorded.

And I dare say we have our hands full with just that task.

[r.cherry]

geeze and all i wanted to do was listen to some music

[dragonfyr]

Then one might wonder what you are doing at the computer instead of sitting and enjoying your music....

(Something more of us should be doing!)

[WMcD]

I'm not disageeing with the merits of room modeling.

To quote Dr. Samuel Johnson, "Like a dog walking on two legs, it is not surprizing that it is done badly; it is surprizing that it is done at all." (He was actually commenting on a woman as a preacher. Not PC these days.) But an interesting comment.

I have two issues. The points being that the analysis is not sophiticated enough to give accurate results in view of real world variables and any result, if true, is not what we want. (Sorry if that sounds snotty, I'm just reporting why all the remarkable math does not give me comfort.)

One: Is anything really modeling our rooms?

For example. My main room is mostly continuous surfaces on five sides. But in the back there is vestibule with a passage to the kitchen, a door to the bath, and a door to a hall to the bedroom which also communicates to the other side of the bath area. Plus there is a pass through window to the kitchen.

Suffice to say this a typical domestic set up which is too complicated to model with any accuracy using the common programs. Even with sophiticated ones, we're getting killed for lack of data. Even if shut, the doors don't act like walls. What to do with the wall with the pass through. Do we include the kitchen in the model?

The model doesn't even begin to take into account carpet and furnature. If we add sizable bass traps and diffusers, how do they fit in? They most likely fix some bad things but the model can't give us A versus B.

We can't play, "What if . . . ?" and mess around with variable except for moving hard, uniform walls which have no doors, etc.

Two:

Do we really want a room with flat response? The K-Horn seems to work because there are room nodes which pile up the bass where the horn response is falling off.

So what we really want is a distribution of modes which match the roll off of the bass horn. The article is not doing that.

Probably the programs do a decent job of modeling a movie theater which is rectangular and there is some uniformity or predictablity to the acoustical properties of the surfaces. Our domestic settings are far more complicated.

Basically, most of us are stuck with what we have. When people start building rooms they might be able to pick a favorable geometry, granted. Then there is the necessary door, steps to the next level, suspended ceiling, etc. I wonder if it quite so favorable in the end.

Gil

[Zen Traveler]

I have been following this thread and down loaded the various articles that dragon has been nice enough to post. As stated above in my previous post, my HT is pretty much the ONLY way it can be setup in my (room) situation. I saw this article and tried to work backwards (again, not using any math;-)

I was trying to understand WHY having such an obnoxious shaped space, I was still getting tremendously beautiful sound. I am curious about the benefits of baffles and in fact may have inadvertently lucked (although I prefer in thinking that I painstakingly designed) into having a semi-baffle situation without really knowing it.

I sit almost 9 1/2 ft from my left & right front channels (and my rears as well in a 7.1 set up) Both front speakers leading edge are budded up against obstacles and form an immediate corner with the front of the speaker. On the left a fireplace (not in use) and the right with a bookcase. It is a small room with a high A-frame ceiling in front-and a small alcove of a room behind me with a low slanted ceiling. I will try and post a diagram soon. I have basically a 9.2 set up with the equipment in my signature line. I can't imagine it sounding any better.