[bpape]

As I said, what you're dealing with here is a damped/bonded membrane. It will only increase absorbtion over a narrow range whose center is determined by the density and thickness of the material behind it.

2" 703
0.17 0.86 1.14 1.07 1.02 0.98
2" 703 FSK
0.63 0.56 0.95 0.79 0.60 0.35

Notice it's better at 125Hz but worrse at 250 and 500Hz? Thin wool won't fix that. Also, a normal wall (single drywall) will already absorb a lot around 125Hz. Do we reallly want/need to put our center there for another peak absorber? Depends on the rest of the room.

1" 703
0.11 0.28 0.68 0.90 0.93 0.96
1: 703 FSK
0.18 0.75 0.58 0.72 0.62 0.35

Here the hump is at 250Hz and little changed at 125hz and lower

Also, for reflection panels, remember that male vocals can extend as low as 200Hz. If you're wanting to deal with reflections in the vocal range, an FSK facing is not desirable and the wool won't reach low enough to compensate.

Now, for NON-reflection panels like on the rear wall and in the rear corners where we just want more bottom end control without overdeadening the highs, we use thicker panels with a membrane over them to accomplish that.

Unfortunately, there is no one single best answer. A room and it's treatment are a system. One must consider the whole thing including seating, wall construction, # of people, room usage, etc. to come up with an accurate and complete plan that addresses all of the needs in the most effective and efficient manner.

Bryan