During the first scenes of the movie Lord of Rings (the two towers)it has terrific loud sounds and my sub would give out vibrating("farting")sounds on some scenes. Does it have to do with calibration since i haven't used any calibrating disc(avia) on my system or the wood floor its on, the sub is bouncing a bit? Would isolation pads do the trick? I do have a JBL (2)8" down firing sub, 200 watt built-in amp. connected to an HK(85 watts/ch)receiver. Do I need to upgrade to a bigger driver? need some comments. thnx.