Yeah, looks like something else because the same was banging this sub for 3,4 months now. Lately my amp started having some tripping issues so I disconnected the coaxials and things went fine, the amp still use to go into protected mode but after some time, finally got fried -_-
Same thing happened to me bro.... but I haven't checked what happened inside
BTW mine was on 0 gain (yeah nearly 0) 