I am setting up my speakers with a Radio Shack SPL Meter and I was curious as to why I get different numbers when I use the Digital Video Essentials DVD as to when I just use the test tones on my Sherwood P-965. I did both tests with the Sherwood at 00 db and the results were dramatically different from one another. For example; just using the test tone from the Sherwood, I ended up setting my center channel to +1. With the DVE the setting was -2. Anyone know why? TIA