A bunch of distorted b is coming from my sub even with the volume all the way down on zero on the head unit?

Please if anyone knows how to fix this or what is causing the problem..please help me. I just got a new sub, it's nice one, I replaced my crossfire 12 with a Treo SSX 12. Before I replaced it, I was having the same problem, but not as bad. The sub would b and beat (not going to the music beat either) on it's own, but not with the volume all the way down. Now my new sub wont even play the music b at all. It just sounds like a bunch of b coming out of it. We tried wiring it every possible way and it does the same thing. Something is seriously wrong somewhere. I think it's a wiring problem. Would you recommend I get a new wiring kit and head unit? Would this fix the problem? What else could it be? It's definitly not the amp or sub, as we tried switching both out and it still does it. Thanks to anyone who knows. I tried asking about this a week or so ago and nobody knew exactly what is causing this. It must not be too rare of a problem, because the same thing happened to me a few years back. The b would beat on it's own but still to the music as well, so I actually listened to it until my amp blew, which only took about 20 mins, but that's a whole nother story, so don't worry about that.