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Originally Posted by azzzy  From what I understand this side effect is significant enough to affect testing data. I keep reading that you should expose as much of your absorber as possible. Why not go further and divide it into more pieces to create even more surface? |
Edge effect is described in articles primarily to explain why testing data can have values greater than 1. ( NRC of 1 = complete absorption, >1 is impossible in real life). So go for surface area in the room.
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I am not too concerned with space. I just want to know the optimal distance from the wall and then see if I can make it happen.
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Old rule of thumb for broad band traps is that the optimal gap is equal to the panel's thickness when mounting the traps flat to the wall.
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Actually Roxul Safe seems to be performing the best at 4". But the table has no data for Roxul Rockboard 80 at 4". Besides I'm thinking of making my bass traps at least 6" thick, if not more. Any recommendations for the thicker absorbers?
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The thicker the trap the less density you want to have. However, at 6", you will still be fine in that 3-4pcf area. If you do SuperChunks you may want to use even less dense like 2.5 pcf... but we're talking getting the last drop of blood out of the turnip here. Use whatever it is you can find locally that is in that density range.
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Can you please explain what it will do? How is it a tuned trap? I think (and I might be wrong, which is why I'm asking these questions) a layered trap would be more broadband than a single density one. By the way, I am more interested in absorbing the lows. I will have diffusors to take care of the mids and the highs.
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It won't be a tuned trap. Panels as you described are broad band absorbers. What it will do is cause you to buy 6 different materials and see no acoustic advantage. Look up posts from Avare and where he describes gas flow resistance. Again back to Bob Gold's.... A 4" thck panel of RHT40 has a NRC of 1 across the measured spectrum. Why change up the materials when you are already absorbing everything? There is no advantage.
You don't mention the size of your room, but if I had to venture a guess based on past experiences with small rooms, you will likely be better off with more trapping and no diffusion especially for someone with limited experience.