Originally Posted by WagBoss
I will be using roxul safe'n'sound.
So basically I can do a stack of triangles, or 3 panel thick pyramid type thing with an air gap behind it. From what I understand, adding an air gap is basically just as good as adding material.
Yes, the total thickness from the front face of the panel, to the boundary behind it is one important design component.
Other considerations include;, if you utilize an air gap, assure the gap is "sealed", from the room, ... as the energy can diffract around the panel and short circuit the effectiveness. The frequency range of interest are large waves, thus the panels need to be large with respect to wavelength. The smaller panels are effective too, just at a higher frequency. When I say "sealed", I mean just assure the material spans the entire width firmly.
Also, this may not apply to you, however total surface area is more important than thickness. What I mean is if you had only one case of rigid 703 insulation 2x4 panels, it'd be best utilized by spreading it all around, and treating four corners, rather than two corners twice as thick. With Safe-N-Sound, many DIY'ers just fill the entire area, and that's great.
Another important consideration, if you find too much MF/HF energy if removed from the listening experience, then you can apply 6mil plastic (Visqueen), or craft paper, to the face off the treatment panel. This will begin to return the energy above about 500Hz. There's even more sophisticated approaches utilizing wood slats. Effectively these facing techniques create a low pass filter in front of the absorption, without altering the overall effectiveness of the bass traps.
How many corners are you considering?
There are varying triangle cutting techniques/stacking, how thick are the traps you're considering?