[azzzy]

As so many before me I am thinking of building my own bass traps. My head is about to expload from the amount of info I've read in the past few weeks. Here are some questions I haven't found a definite answer for:

1. I am thinking of using Roxul Rockboard. It comes in various densities from 4 pcf to 8 pcf. From what I read I understand the denser the better. Is there such thing as too dense? What would be the optimum density for the absorber material for low freq absorber?

2. The edge effect. Since exposed edges of the absorber contribute to more absorption would it make sense to place two 2'x2'x6" squares (one above the other) with an air gap vs. one solid 2'x4'x6" absorber? What would be the optimal air gap? And if the above is true why not split it into 4 1'x2 pieces and place them one above the other with gaps between them? Anybody done that?

3. Placement. I read that the common space between the wall and the absorber is 16". Does the effectiveness of the low freq absorber diminish once it's moved farther from the wall? If not, would it make sense to place a couple of low freqs absorbers somewhere in the middle of the room (in addition to the absorbers in the corners, of course)? Or the 16" gap is the fartherst the absorber should be away from the wall?

4. If I have a bass trap in the corner does it have to touch the walls or is it better when it's farther out into the room? Can I place something relatively thin behind the bass trap (like a PA speaker stand - a 3" thick tripod)?

5. Different densities are optimal for absorbing different frequencies. Does it make sense to make an absorber layered with different densities? For example, using Roxul:

a. 4" Rockboard 80/4" Rockboard 60/4" Rockboard 40. The densest material is facing the room and is farther away from the wall, which is optimal for absorbing low freqs. The least dense is the closest to the wall but it's OK since the higher freqs have shorter wave lengths. Would this work or would the higher freqs not pass through the denser material to the less dense one?

b. 4" Rockboard 40/4" Rockboard 60/4" Rockboard 80. The least dense material is in the front. It absorbs the higher freqs and lets the lower freqs through towards the more dense material where they get absorbed. The higher density is closer to the wall though. Would this work better than the a. version above?

c. 2" Rockboard 40/2" Rockboard 60/4" Rockboard 80/2" Rockboard 60/2" Rockboard 40. The densest material is in the middle between the less dense ones. This allows it to be resonably far from the wall and at the same time not reflect the higher freqs before they get absorbed by the lower density materials. Would this work?


***OK, I understand this might be a lot of questions for one post. Perhaps I should have made each of these into a separate thread. Please let me know if that's your preference.