The 8lb would be fine for bass absorption. I would use the lighter density for the side wall reflection panels.
Correct. Which is why the 2x6 would leave 1.5" off the wall.Just thinking about getting better absorbtion with a gap between the panal & the wall.
using a thin board say 1/4" to 1/8" thick.... but have a square frame build around the edge on the back side of 1x2 material allows the entire middle of the panel to be loose but creating a back for the fiberglass to lay against.I think the backer board would defeat the purpose of the gap (would act like the wall).