[DanU]

Like jadison said... first check the wiring. It's amazing how many things are caused by a loose wire somewhere.

I assume you're using a powered sub. Either the speaker or the amp inside the sub could be fried. You could try swapping out the speaker with a similar one to see if it will still work. You'll need to find almost an exact match in order to maintain the same audio quality. Usually this means ordering a new driver from the manufacturer.

If it doesn't work, then maybe the amp is fried. Usually the output transistors are the first to go. If you're into fixing stuff... you could try testing the transistors and replacing any of the faulty ones.

If you're not technically inclined (hey... you must be... you're a techimo member !) then I'd recommend sending it to a repair shop if you've determined that a simple wiring error isn't at fault. Replacing the driver is somewhat easy... but doing the transistors can be a pain.