Ethan's membrane traps: using plasterboard instead of ply?

hi I need to cure a peak at 68Hz (easy to see where it's coming from, parallel brick walls behind speakers and behind listening position 5m apart). Ethan's membrane traps seem a sensible place to start, but the LF trap he describes using 0.25 inch plywood apparently only works down to 80Hz. Would I be right in thinking that a heavier material for the membrane (plasterboard) would reduce the band of frequencies over which it resonates? thanks

Bremen, > Would I be right in thinking that a heavier material for the membrane (plasterboard) would reduce the band of frequencies over which it resonates? < Yes, but I don't know if plasterboard is the best naterial for that. I'd use 3/8 inch plywood. --Ethan