Room Acoustics Forum by Rives Audio

Angling of absorptive panels

124.185.232.177

I think in general there's a tendency to wall mount acoustic panels but that hasn't been an option in my room. If you want to place panels in front of windows, a bookcase, and at the side of an archway room entrance, wall mounting is not an option. You go with free standing stand mounts.

Until recently I had always placed my panels parallel to the walls, in basically the same orientation as a wall mounted panel. A few days ago I tried a little experiment. My Mondo Traps are placed so that a mirror placed flush on the front of the trap at the midline identifies the first reflection point. What I did was to rotate the trap slightly on that midline so that the incident ray now struck the trap at right angles.

My reasoning was:

- that portion of the sound reflected at incidence now is reflected back towards the speaker rather than towards the listening position, weakening the first reflection even further by virtually eliminating it (there may still be some very slight scatter of reflected sound but the bulk of the reflection is back along the incident path);

- while I haven't been able to locate a specific comment anywhere, I have a strong feeling that absorption is greatest when the sound strikes the panel directly rather than at an angle, and that absorption decreases as the angle of incidence of the soundwave reduces below 90 degrees.

My results tend to support those views. Overall there was a slight gain in coherence and naturalness of the sound but the most noticeable result in my room was a reduction in vocal sibilance. use of absorption had previously reduced sibilance and the change from DIY panels to HF Mondo Traps had been beneficial as well, but angling the panels slightly as outlined above almost eliminated sibilance entirely, to the point where I'm wondering whether the trace of sibilance I now occasionally hear is simply the level present in the singer's voice at the time since all voices do have a tendency to slight sibilance on some "sss" sounds.

If others have some free standing panels, they may like to try this out for themselves if not already angling their panels. Use something like a book on the floor to mark the panel's original location and then start rotating the panel till it directly faces the speaker whose reflection is being treated.

Unfortunately it's not an option for wall mounted panels unless you attach them to the wall by hinges along one side.

David Aiken

Follow Ups:

RE: Angling of absorptive panels - Ethan Winer 11:40:03 07/04/08 (0)

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