Without knowing the speakers, I have two possible ideas. The first (which is probably the cause) is you do not have a good ground! As soon as your bass hits it is shaking that ground wire just enough to losen it and that will throw you into protect mode. Check your ground! The second, and this probably is not the cause, but your sub has a lower OHM indepedence than your amp can handle. Check, if you have a 2 or 4 OHM DVC sub, it will be 2 OHMS at the amp, which could be lower than your amp can handle, Im not really sure about that cause your amp should be 2 OHM stable. Check your ground buddy, Im sure thats the problem.