Hi all! I have a Polk PSW50 home stereo subwoofer and the speaker vibrates to the point of making a discernible buzzing (and annoying) sound. When I touch the lower portion of the speaker gently, the vibration stops. Or when I lay the speaker on its side it stops. I've tried sticking my hand up into the cavity of the speaker, moving the insulation around etc..Anyone have a clue on how to fix this?