Alan:
You might find this short article interesting which expounds on another element of Toole's recent work and the importance of NOT over treating small rooms with absorptive elements [specifically as such relates to speech intelligibility and center channels and more generally the inapplicability of paradigms developed for large spaces to small rooms].
http://www.audioholics.com/education/aco...ent-perspectiveWhile I have long understood the importance of the caution to not over treat critical listening spaces with absorptive elements, I would object to the idea that early reflection control and similarly located absorptive placements implemented to diminish SBIR interference are in and of themselves bad ideas. Collaterally I would readily agree that modal resonances and early reflections are not bad things... its all about balance in my opinion, you can have too much early reflection input and garble the stereo image – you can have too much absorption and render the room dull. Neither is best practice.
We have found by that taking a broadband approach to absorptive treatment of small rooms [using absorbers on the order of 4” minimum thickness which work more or less smoothly at all frequencies – lows, mids and highs] one can greatly reduce the surface area of absorptive treatment used overall and in such cases yield a critical listening environment that does incorporate a modest amount of early reflection control but retains a stellar “spaciousness" and a “realistic the soundstage”. This approach also saves money in that you use fewer panels, and can achieve smooth low frequency response with fewer subs.
When properly balanced in a room with rational fixtures and finishes we find that modest early reflection control can enhance the depth and clarity of the illusion of the stereo image, diminish SBIR problems, and make for a larger “sweet spot” without killing the “snap and sparkle” of the room, or causing speech intelligibility problems.
Also, low frequency control through absorption is in our experience not simply a matter of dealing with “impossible standing wave problems”… but rather a means to smooth out the rough responses inherent to all small rooms arising form low modal density at low frequencies and unavoidable SBIR problems. Here is an example:
The above graphic is a series of 13 low frequency response measurements taken in a small room. The first frame is a bare room with no treatment. Each successive frame is the same measurement taken after the addition of a single 4” thick absorption panel. In the thirteenth and final frame a total of 12 panels have been added. Note the significant smoothing… this sort of treatment makes a profound difference in the accuracy of your system low in the band of audible frequencies.
Controlling low frequency distortion and smoothing the system/room responses at low frequencies and diminishing SBIR distortion can greatly enhance the listening experience – and diminishing strong early reflections can greatly sharpen and clarify the stereo image. In my view, the trick is to find ways to accomplish this without making the room exhibit “those dry, sucked-out qualities” you properly caution against.
