Polk Subwoofer sound problems

  • I have a Polk 110 powered subwoofer, approximately 4 1/2 years old. Recently, it has begun to thump at low volumn after the receiver and TV has been turned off. It sort of sounds like a low heartbeat. I did some adjustments and haven't noticed much of that since, but now it at times has a sort of hum or static coming from it when the sound of the TV and receiver is muted. I am wondering if the sub is going out, or if there is something I can adjust to fix it.

  • It's more likely to be an amplifier issue than the sub itself, but this is car audio section, not the home audio section, so I'll move it.