I'm relocating my 901 speakers and I'll have to insulate and cover the wall behind the speakers with wood to get the best sound from the speakers. Does anyone have suggestions as to the best type and thickness of insulation behind the wood wall! Any suggestions for the best wood to use behind the speakers? The current material is metal barn covering which will not allow for a good sound being reflected back. I'm planning to insulate in front if the metal building wall and then finish the wall with solid wood or composite material. I need suggestions please.