and I learned a few things. 1. My ears are not the best way to calibrate my speakers. using the SPL, I adjusted the speakers and the system sounds a few times better, most notably in the surrounds. 2. I am a Bass pig. Before the SPL I had the receiver set to +4 for the sub. The SPL says -4. I now know why my ears hurt when I watched a movie at seemingly low volume levels. The bass was was way over the top, with the rest of the sound at ~80db, the bass probably way past 100db, and that was without considering peak.levels. 3. Most importantly, I should have listened to to all the experts that said a SPL is a must have!