I have recently upgraded my HT system with a new amp and speakers. The only one left is the sub, but I'm not sure what I got. I purchased this sub off of Ubid.com 4 or 5 years ago and never gave it much thought. It is a 10 inch solidly built down firing sub. It was originally part of a whole HT in a box from Hitachi. All I wanted was the sub and at the time it was a good price. Anyway, before I go out and find something new, what can I do to measure the performance of this? To me it sounds good, but maybe because I have never heard a good one I'm in the dark. I have the Avia calibration disk and the RS spl meter. I listen to the tones but don't understand what I'm trying to hear. Maybe someone can give a simple explanation of what to look for. Maybe I don't need one. Thanks.