Quote:
jagman wrote:
 It's interesting because You're the fifth informed person I've received advice from and all have said something different. One says diffusion from close distances isn't effective and heavily advocated high density absorption on the rear wall (to reduce the cancellation that results from lower frequencies bouncing off the wall). Another sells absorption but actually recommends against it but only behind the seated position (especially for two channel music), another only recommends absorption at the corners (wall/wall, wall/ceiling, and especially the tricorners) but not at first reflection points, and another recommends diffusion on all walls and absorption on the ceiling and floor. All are repected people in the business and all provide data that they think backs up their recommendation. Basically, I think it all comes down to taste. No system, let alone a room, allows ultra accurate reproduction of sound; the best we can do is come up with reproduction that we like. |
Some of these recommendations leave me puzzled. The purpose of the surround speakers in the rear hemisphere is to provide diffuse/non directional spaciousness to counter the tight/dry and damped front speaker/hemisphere combination. The whole principle of the dipole speaker confirms that purpose, as does the fact the Dolby recommendation require that the rear speakers not directly fire toward the ears. If you damp the wall behind the listening position, you defeat that purpose. If we are talking about a large professional theater, or dubbing stage I can understand that recommendation to help control long reverberation times that cannot effect dialog clarity and preserve transient information. 4ft is enough room for diffusion to work, because that is exactly the distance from my listening seat to the rear wall and I use diffusion on my rear wall. Measurements from the listening seat confirm its effectiveness.
In the installation I have done, I follow the principles of Dr D'Antonio from RPG acoustics and he recommends that the front 2/3 of the room be absorptive, the rear 1/3 be diffusive, and the ceiling be diffusive. Its alot more technical than that, but it works with the principles of THX acoustics, and Dolby recommendations. I agree with lining the wall/ceiling junction with absorption. However NOT recommending absorption at the early reflection points just kills image specificity in the front soundstage. It sounds like alot of these guys are into two channel music and not hometheater specifically. The recommendations for music only, and hometheater are quite different. In recent acoustical workshops that I attended, most acoustical professionals are moving away from too much absorption in small rooms, and recommending more diffusion because it makes the room sound more natural and larger. Too much absorption makes a room sound small, closed in, and not very eveloping. Too much diffusion causes a lack of image clarity. The right combination of both in the right places results in a room that sounds natural, spacious where it should, and tightly focused image wise where it should. I prefer science first, taste second because I believe you have to have some point to begin in order to adjust to taste. I don't sell anything, my job is to recommend what makes a room sound natural, and the recommend the products that get you there.
The science is there, so no guess work is really needed on this issue. Every room is different, but there is a solution for all spaces.