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Does anyone have any guidance on the placement of room treatments for planar speakers vs. direct radiators. My room treatments were sort of placed with DRs in mind and I'm wondering if I should change anything.http://i20.photobucket.com/albums/b249/imahawki/IMG_5951.jpg
http://i20.photobucket.com/albums/b249/imahawki/IMG_5950.jpg
http://i20.photobucket.com/albums/b249/imahawki/IMG_5952.jpg
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Maggies (line soure diploes) are realtively forgiving compared to typical direct radiator speakers. The line source helps to minimize floor and ceiling first order reflections and the dipole really helps to get rid of that nasty first wall reflection. So what to you get in return for that acoustic magic? Well you haveto deal with the rear energy... You would like the frequency balance to retain much of the character of the forward radiation. Of course you could get absorb all that rear energy... but that makes the sweet spot even tighter that normal... I like nice diffusion for the rear back and rear side wall. If you want to add absorpsion - do it in the middle rear - though I just continued my diffusion in from the corners.
as a test piece and listen carefully to your setup as-is, then with the treatment panels removed, then with them replaced one at a time. This should make clear if these are helping or hurting the sound-stage performance. If the panels don't affect the sound-stage, and there is little depth to it, then you have other problems such as RF noise that prevent you from hearing the effects of the treatments.Another test is to clap your hands and listen to the room response before you remove the panels, and after. If you hear a sustained metallic ringing without the panels, then they are damping your slap-echo and you might need equivalent amounts of treatment but in different locations.
You might need some treatment behind the screen, where you would see your reflection if the wall were covered with mirrors. This depends on how reflective the screen is to sound.
If those are woofers in the ceiling, you might try disconnecting them from the amps and shorting their leads when listening to two-channel music. They will interact with the room sound and absorb certain frequencies. Shorting the leads will act like brakes applied to the cones.
For optimum bass from the Maggies, look into the Cardas formulas for speaker placement.
My room (14 x 20) is relatively "dim" acoustically (opposite of "bright"), in that it is carpeted, there are drapes on portions of the front and side walls, etc. Bookcases extend along most of the rear, front, and portions of the side walls. The sound was somewhat laid back. Instead of adding absorbing material, I added reflective material, specifically, smooth-surfaced wood flooring layed on the carpet in areas in front of the speakers (3.6R's). The flooring extends about four feet from the front of the speakers toward the listening area. This may sound heretical, in that the usual recommendation seems to be to dampen the the first reflective surfaces. But in this case, it seems to improve the sound, making it brighter and more dynamic. Obviously, the extent of reflective surfaced area can be adjusted by using more or less of the flooring material (strips of .25-inch thick composite flooring). Because of WAF's, I normally pick up the flooring and store it behind the speakers when I'm not listening critically.YMMD, but in this case, it seems to improve the sound substantially.
Your tweak is a good one for Maggies. A Maggie looks something like a line source at the important frequencies, and the ribbon tweeter is a good approximation to one because it is so narrow. An ideal line source would extend to infinity above and below the listening position. Your reflective floor surface covering provides an acoustic mirror effect that extends the line source to well below the floor level. The ceiling does the same thing in the upward direction.One of the all-out approaches to a true line source is the Dali Megaline. Well worth an audition if you ever get the chance.
Point-source speakers, OTOH, and the side-walls of Maggies, require first-reflection treatments because the mirror images of the speakers act like independent sources that have time delay relative to the real speaker.
with a pair of 1.6's is:(1) Absorption and diffusion at the corners and the center of the wall behind the planars.
(2) Leaving the walls pretty much alone along the side walls from the front of the room to the speaker plane. (An oil painting hangs on one side [drywall] and a partial section of a window insert that serves as a very shallow bookcase on the other, siding-paneled side.
(3) Absorption/diffusion at the first and second reflection points.I've treated the rest of the room as well, but the foregoing is what I'd consider basic in my setup.
Pictures and diagram at the link below.
Jim
http://www.geocities.com/jimtranr/index.html
So is there a rule about not having absorption right behind the panels? Because I do.
in this room, I obtained the best overall combination of spatial presentation, frequency balance, retention of a focused "phantom center", transient snap, and perception of musical flow by keeping absorption a discreet distance from the panels and, as the diagram indicates, facing the diffusor section of each trap into the room.Going fully absorptive (by turning the diffusor side to the wall) with any of the traps in some cases gave a slightly greater illusion of depth but at the expense of performance "liveness" (e.g., in the rendition of spatial "air"). And placing traps (even with the diffusor side out) about every three feet along the front wall (as well as along the side walls between the front wall and the speaker plane) turned out to be too many, too much.
What I've found along the way is that randomizing (diffusing) rather than killing (fully absorbing) reflections yields--within the boundaries imposed by engineering and producing decisions--a more realistic illusion of a performance in space...at least under the listening conditions that apply in my room. I wouldn't go as far as calling it a "rule", but I'd suggest it as an approach worth trying.
you will hear three different "rules" from three different inmates. my suggestion is to take an impulse response measurement and look for early reflections. once the impulse response is clean. check cumulative spectral decay in the midrange and lower tweeter frequencies. you want a quick drop then it can come back a bit after about 5ms. i think you will find it hard (expensive) to "overtreat". on the other hand, if you treat behind and between on the front wall, many have acceptable results because the first side reflection often resides in the area of dipole cancellation depending on toe in and other room geometries.
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