Questions on acoustic treatment
- From: alan <no-longer-valid@xxxxxxxxx>
- Date: Wed, 28 Sep 2005 07:23:05 GMT
The setup:
Martin Logan dipole speakers
14'x12'x8' room with two openings against one of the walls- an opening into a small kitchen, and a door into a bedroom.
I'm trying to do some acoustic treatment to improve the imaging of the speakers. Here are the three main approaches I have considered:
1) Bass trapping, via stuff I read from Ethan Winer's pages. For now, I might leave this area alone since I don't want to play around with fiberglass or pay a lot for low frequency absorption.
2) Stuff from Eigth Nerve. http://www.eighthnerve.com/ Their philosopy seems to just be jamming some stuff in the corners and not worrying about 1st reflections/absorption, etc. I think they feel that
a) if you try to absorb or diffuse, you'll only get the high frequencies and botch everything else up, so don't bother trying.
b) if you only treat the first reflections, then the 2nd, 3rd, etc will botch everything up, so don't bother trying.
They don't seem to be popular right now, but I have read one or two good reviews. Does their technique seem sound? It seems to be fairly cheap and easy to set up.
3) Treating the reflection points. There seems to be a good writeup at http://homepage.mac.com/tzagar which addresses the specifics of dipole speakers. I think the gist of the advice is:
a) use diffusion behind the speakers
b) use diffusion/absorption on the side walls
I have a few questions regarding this implementation.
If you intend to diffuse/absorb, what frequency do you need to go down to to get good imaging? I'm assuming that for the lowest frequencies, you'd be treating the corners anyways.
I've also read somewhere that the smaller the room, the more you should favor absorption. So what should I do in my case?
In the case that I can only afford 1-D diffusion, should I "spray" the signal horizontally or vertically? I have carpet, btw.
What I've done so far is find a few scraps of (thin) Sonex foam laying around in my lab, and put some on the wall behind the speakers (not directly behind the speaker, but more towards the center of the wall). For the sides, I have one bookshelf and one probably-not-properly-placed piece of foam. What I seemed to notice was that I could more easily localize sounds that came from positions between the speakers, but that some of the "sparkle" of high-pitched noises and plucked strings, percussive strings, etc were lessened. It also seemed that the image moved less with head position. My guess (assuming this is not placebo effect) is that I improved the imaging because sounds that were supposed to come from between the speakers were now mainly generated by the speakers, instead of bouncing off the wall at that position. And that the loss of "sparkle" was due to the thin foam only absorbing the high frequencies and not fixing the reflection problem for mid frequencies.
For now, my budget is only a few hundred dollars, so I was thinking of getting some stuff from Auralex, like their StudioFoam Metro (since it diffuses a bit also) or maybe some of their diffusors too.
.
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