Building my first ever H.T. room and i'm wondering about acoustics and hard walls, the floor will be carpeted, but I would appreciate comments as to whether I should curtain off the side walls (and maybe the rear?) The room dimensions are 20ft long by a little over 13ft wide, with a height of just over 8ft, I have used soundscreen insulation to the only wall that faces to the rest of the house, the other three walls are lined inside and bricked outside. I'm concerned that the room may have too much echo, if I leave the internal walls as they are, will the sound be too harsh? What materials for the internal walls have others found to use that will produce the best sound for a moderate outlay? Wifey is already threatening to cut up all my credit cards...LOL.