I have two JBL HTI88 (dual 8") subwoofers consealed on either side of my TV in the home theater room. I didn't have any vibration issues for a month or two initially since I constructed. But now, I have started to feel lot of vibration and rattling noise from the walls (unfortunately its too late for me to realize that I shouldn't have gone with steel frame but wood for the drywall). Since the subwoofers are fitted against the wall, its located 3 feet above ground and 5 feet below the ceiling and it has 30 inches depth - in a hollow space inside the wall. Will building a box, and insulating the box - for the woofers help? In this case, will I need to have a pole (hole) in the box? If the pole/hole reside inside the wall, then I suspect the vibration to continue. JBL has a back box (HTI88-BB) which they recommend installing before drywall. Does anyone know anything about how much this can control the vibrations? This sounds an expensive alternative for me as it will cost me over a grand for setting up (I need to rip off the wall, install this back box [which itself costs #350 each], drywall and paint). I will appreciate for any of your suggestion(s). Thanks. Chandra Sekhar.