Presumably, these are 4" or so rigid fiberglass, yes?
Yeah - more info below in quotes. I think the MRT (long thin ribbon) reflection isn't hampered by the corner positioning. When flat against the wall, they didn't work too desirably. They were knocked up by one of the chaps that visited.
"I have the following design specifications for the panels. The figures quoted are the DESIGN specifications based upon the published reverberation room method for the materials used, and based upon NO air gap behind the panels:
Before looking through the figures, it's important NOT to get too hung up on them. Anything with an absorption coefficient of 0.7 or greater is said to offer good sound absorption at that frequency. The figures drop off at low frequencies as these are harder to absorb, but an air gap behind the panels significantly increases efficiency since the sound that makes it through the panel is reflected back into the panel and is re-absorbed.
100mm panel:
Frequency (HZ): 125 250 500 1000 2000 4000
Absorption Coeff: 0.84 1.2 1.2 1.1 1.1 1.1
50mm Panel:
Frequency (HZ): 125 250 500 1000 2000 4000
Absorption Coeff: 0.24 0.73 0.93 1.1 1.1 1.1
As you can see, the 100mm panel is 4 times more effective as a sound aborber at 125 Hz than the 50mm panel. To increase the absorption effect, an air gap is left between the wall and the panel (hence free standing panels are said to be more effective than panels hard up against walls since the sound is reflected off the wall and travels back through the panel).
For that reason, one of my 100mm bass traps (300mm wide) placed across the corner should be more effective than a 200 or 300mm foam bass trap and to my mind would look much nicer!
As you can see, from 500 Hz upwards, there is little to choose between the 50mm deep panel and the 100mm panel. I will offer 50mm panels for wall fixing on the side and rear walls.
The 50mm panels are most effective when placed at the PRIMARY reflection points which are the side walls mid-way between the loudspeakers and the listening position and the ceiling mid way between the loudspeakers and listening position. I would advise using 100mm panels behind the speakers and in the corners.
Panels behind speakers and in the corners is a good place to start, only adding more if required. You can over-do it and deaden the room and reduce SPLs if too many are used.
On a practical note, the 100mm panels are MORE RIGID and should be used for all free standing applications irrespective of placement. The thinner panels are for wall or ceiling fixing.
Hope this helps. "