I sold my old system to a buddy back in my home state. It's a Fi BTL 12" (2nd gen) on a hifonics brutus 2610d. He called me last night saying that he hadn't played the system in a little over a week, but when he got back in the car, the sub was hardly playing, but would occasionally kick back in for a few seconds. He said the amp stayed on without going into protect. I had him check his Subwoofer HU setting, check the RCA's, and the speaker wires connected to the amp. He said everything looked to be fine. The only thing that I can think of is that a wire came loose from one of the coils in the box and the sub is only seeing half power and only on 1 coil. Any other thoughts on what the problem could be? I don't know what could have happened to it from just sitting for a week with no play time at all. Temperatures have dropped a lot over the week. I don't know if that could cause something to go wrong or not. What do you guys think?

I am thinking loose speaker wires. I'll double check everything before playing it again even if I have to unscrew the subwoofer from the box and look inside.

Blew a speaker myself with bad box<>amp wiring.