If so, here's a little trick I learned from Ed Schilling of the Horn Shoppe.
Hopefully your subwoofer amp will have a mono switch, like the one shown in the picture.
1. Get yourself a cheap throw-away pair of interconnects, and cut the two male RCAs off of one end.
2.Strip the wires, solder a 10k, 0.5W resistor in series with each positive wire, and hook the bare wires up to the output terminals of your main amp, right along with your speaker wires. Maintain phase.
3. Plug the two male RCAs into your "line in" input of your subwoofer amp, set it to mono, turn the sub amp on, and enjoy.
Its always worked for me.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
