Determining Optimum Room Dimensions for Critical Listening

[dragonfyr]

----------------

On <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />4/24/2005 4:42:27 PM William F. Gil McDermott wrote: <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

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

To quote Dr. Samuel Johnson, "Like a dog walking on two legs, it is not surprising that it is done badly; it is surprising 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 sophisticated 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. Is this all?????

Suffice to say this a typical domestic set up which is too complicated to model with any accuracy using the common programs. Even with sophisticated 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 furniture. 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.

Sure they can. And not only that, but measurements can provide data for iterative feedback or proof of performance verification.

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

Sure they can. Addressing surface characteristics and various treatments can be tried ad absurdum to determine the various resultant effects given the various topologies considered.

-----------------------------------------------------

My intent is not to sound like a jerk, nor to pick on Gil! Quite the contrary, rather I just wanted to use this response as a foil to make a couple of points, as Gil has expressed a couple of points that repeatedly arise in various places. So, thank you Gil!

But, in reaction, this is absolutely incorrect. If your tools cannot do this, my question is what tools are you using? Programs such a CATT-A and EASE can! And they operate on as exact a 3space architectural model as YOU choose to input.

And as far as the reflective/transmissive/conductive co-efficients of the room surfaces, this is a fundamental and critical component of such modeling. And the complex behavior of these surfaces is WELL understood and able to be modeled with uncanny accuracy!

May I inquire as to what tool you are aware of that does not utilize this data? Who is operating it and not accessing and inputting this data accurately and to the detail necessary? Why not? The fact that one is not aware of the proper tools nor of the available data does not render the discipline inadequate. It simply renders whomever is doing this negligent or the specific tools they are using inadequate. And yes, it DOES require the proper tools! Just as acoustical room measurements require more then an SPL meter or and RTA!

Additionally, acoustic modeling is but ONE step in a process. It is a prerequisite and preliminary step! This is followed by actual measurements, treatment, and proof of performance measurement and listening correlation. Any process that does not employ this is not a valid process.

I think what we are running into here, is not a disagreement about the potential for the tools, but an unawareness , and ignore-ance, of just what professional tools are available and being actively used. Granted, all of these are not practical for a hobbyist who only seeks to optimize his or her room. But these tools ARE available to acousticians, and indirectly to hobbyists if they would simply take the time to invest in their room like they do regarding an electronic device!

And to jump on that tangent for a second... I get a kick out of reading the posts that go on and on over seemingly trivial distinctions (should I mention the SET debate ) or he virtues of spending thousands on a turntable, etc., while few if any have made any real investment in actually employing the CURRENT state of the art tools to have their room analyzed and then to address the treatment in a planned manner with proof of performance testing. It costs no more then one of these electronic toys, yet will provide a greater return then any other component short of perhaps the speakers. And it will optimize their resultant performance too!

Instead, when it comes to room treatment, we seem stuck in the shotgun approach to trying lots of different medicines in an attempt to treat "some kind of illness, the exact nature of which we are ignorant, except that we know we are suffering from something".

And I am amazed at the seemingly constant dismissal of such analysis and treatment as too many simply dismiss it as having no correlation to listening. NONSENSE. Perhaps the methods that individuals do on their own do not, but that is NOT the case with qualified analysis and treatment.

I truly wonder where people are getting their information. And I suspect that too often it is from the 'head up their posterior' magazines that talk 'about' A/V rather then those who actually do it.

And if you need references to state of the art practitioners, email me!

I personally find it quite humorous that so many will spend more time endlessly debating as well as spending more money on speaker cable, interconnects, capacitors and exotic AC power cords then they do room analysis and specific treatment.

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.

The basis of the folded horn is room modal anomalies??

And do we want flat response? Let's see, why all the preoccupation with capacitors, AC cords, interconnects, and the infinite number of adjustments that contribute less and less ROI compared to the interface of the speaker and room? But room optimization is not about correcting for your speaker's inherent anomalies. But it does address anomalies introduced via the interaction of the speaker with the room.

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 predictability to the acoustical properties of the surfaces. Our domestic settings are far more complicated.

No! With all due respect, you are NOT aware of current tools!

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.

Qualified room analysis optimizes the space you have! Not the space you fancy you want!

Bottom line, optimizing the room will make the second most dramatic positive impact next to the selection of the speakers.

This area of audio has progressed more in the past 30 years then in the entire span of history before it. And it continues at an accelerating rate.

But, as always, everyone is free to focus on the advantages of Mylar versus polypropylene caps or stranded versus solid core versus RG6 coax, or in squinting and holding your head tilted precisely if you choose.

But let's at least address the realities of acoustical methods rather then depending upon hearsay assumptions that are dated at best. The advances in the past 30 years have been absolutely astounding. And to ignore or dismiss them based on very dated or simply erroneous assumptions is not an accurate assessment of the field.

Again, thanks Gil for expressing your ideas!

...Sorry for interrupting the latest debate over cables or Monster or Bose....