I just recently purchased an ACI Force to go with my Hales Concept 2 main speakers. ACI includes a test CD with test tones from 15Hz to 200Hz to calibrate the sub in the room. They recommend calibrating at 70 dB. Using a Radio Shack Analog SPL (and using correction values) I am able to calibrate the in room response from a low of 65dB and a high of 75dB. I'm using 100 Hz and 20 Hz as reference points that are exactly at 70 Db. The SPL meter in on a tripod in my listening seat. My question is...how does this calibration compare to others out there? Should I be able to get a flatter response? I've tried about 10 different setups with various sub positions, crossovers, etc. and +-5 dB seems to be the best I can get. Thanks.