I calibrated my new PB10-ISD this weekend and noted that several of the test tone freq's from snapbug (16Hz, 45hz, 50hz, etc.) cause the sub to rattle horribly as though the VC or magnet is making physical contact with the subs innards. H/K AVR525 settings -> Speaker Levels -> Subwoofer -> -5db PB10-ISD settings -> Gain -> 25-30%, Phase -> 180deg System previous calibrated to 75db with H/K AVR525 internal test tones and 85db with AVIA DVD which is -3db on the AVR525's dial. Whenever I would hit one of these offending freq. I would immediately mute the system because I don't want to damage my sub. The SPL readings range from 76db to 103db depending on the tone. The sub seems to sound ok with movies and music but it doesn't seem right that some of these frequencies like 45hz which is right in the middle of its operating range (18hz - 100hz) would cause this kind of behaviour. Thoughts??