Heres my guess...

Its a 4 pole relay with normally open and closed contacts. Low voltage DC coil (probably an ice cube 12v automotive relay) hence the power supply. The relay input side is the from the amps and the output side is jumpered out and going to the speakers. Very cool setup and custom box! We built stuff like that in motor controls/PLC labs. And yes, I'm a dork for knowing that and posting. grin