Jeff, there were some postings back a few months ago that seemed to indicate that the volume knob on the 500 was modified so it had to be turned up a bit more.

It's not any less powerful, but it seemed that many people found they had no "range" to work with on the knob...i.e., they barely turned it up a couple of notches to have it blasting!

::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::