Last night I calibrated my stereo channels with the sub ofcourse to reference levels. Then I went on to measure the freq response of my system in two channel by measuring SPL levels at seating position while sending 20-20K warble tones. My freq response is quite flat from 100-10K (+/- 2.5 db) but below 100 Hz I have two nasty peaks at 80 hz (92 db) and 40 Hz (103 db). Is that normal? if not what can I do apart from moving my sub in order to address this?