Not familier with that sub but the Axiom EP500/600 have a ground screw on them to help with hum.

I think I read a post by Alan Loft that if the sub hums with no line connected, there might be something wrong with the amp in the sub.

http://www.axiomaudio.com/boards/ubbthreads.php?ubb=showflat&Number=187452#Post187452


paul

Axiom M80, VP180, Qs8, EP500
Epson 3020
Rotel RB-880
Denon AVR-990