MMMM well don't know, but I found some mega power thing that the wire led to another smaller thing that was under the hood that hooks to a stereo system and wires that lead to the back. I'll have to look to see what it says, the PO must of had a big setup and maybe some sort of roll out speaker system. Also found a 12 cd disc or maybe 10 disc Pioneer remote shuffle player under the back seat with a remote. Just new info I found today. Anyway what ever it is I'm going to pull it out and hope cosmic dust goes with it. It's a Alpine deck and Infinity speakers in the back in head liner. At any rate I don't need a thumper. The in dash deck is good enough for me. So maybe this is solved if it was for a slide out box with big speakers or maybe a portable bar?