Have a new Velodyne sub(cht-12"), and am struggling to properly calibrate it with my system. Currently, I'm getting the issue where it frequently puts out a thumpy sound, like someone tapping a microphone. What might you suggest to smooth out the performance? I've tried many things: bringing my fronts back to large and dropping the crossover to 40Hz. Adjusting the cross through the 80 to 40 Hz range. I seem to avoid it when I have the fronts set to small, and the cross to 80Hz, but then I seem to have a large gap in my low bass range. I just calibrated my speakers with an SPL, and have the AVIA dvd ordered, but in the meantime, it's a bit frustrating. Current setup is a pair of PSB Stratus Silveri's, (35hz-21,000hz), with Athena ASB1's for surrounds, (C7 center on order) no center for now. Denon avr-1700 driving the system. If you've perhaps encountered this issue yourself and figured out a process to fix it, or just happen to know what I'm going through and can lend a helping hand, I'd be truly grateful!