There is a great fix for this problem at low cost-outlaw audio ICBM bass management unit. Outlawaudio.com
Twc, if you are using a dvd player for music, check the audio menu out on the dyd player. The subwoofer may be set on "none". Also check all connections where they are placed. If the bass comes in and out while music is playing, you could have a bad interconnect or a loose rca on your anthem, source or sub.