i agree that anything behind drywall wouldn’t work very well. Having a smallish room I did end up killing 2 birds with one stone. I had an acoustician design the room and I built it while the speakers were being built. I have no drywall inside the room which allowed for absorption to be built into the walls and ceiling. I do have double drywall on the outside with MLV between the layers. The ceiling joists have Rockwool in them. It turned out quite well sound proofing wise and sound quality wise. Happy listening
Ron