I spent about seven hours yesterday trying to calibrate my speaker levels appropriately to diminish sporadic plummets in frequency response. Damn this hobby is a curse. Anyway, with my SPL meter appropriately positioned, my speaker levels would all adjust well (FL=0, FR=-1, CEN=-1, SR=+3, SL=+8), but my subwoofer would give me surprising results on the SPL meter. With the physical volume knob on my subwoofer mid-level (90 degrees), and my receiver outputting to that specific channel at -10dB (while testing with master volume @ reference -8dB), the SPL would read the sub emitting over 90-100 dB. I, myself, could hardly hear the sub when the meter was off the charts. Yes, I understand that frequencies below 40Hz are hard-to-hear (especially w/o a golden ear). After testing, I was forced to put the sub-channel level back to 0dB gain, and turn the volume knob on the sub up to 3/4 volume. Without these readjustments, I severely lacked bass. I have a radio shack digital SPL, could there be something wrong?