1994 Ford Explorer Whare are my cars speaker wires?

Interior problem
1994 Ford Explorer 190000 miles

I am installing a new radio. I have found the, pwr, grd, swt. Gnd. And are hooked up. I found a small (looks like a remote cd plug, 8 very small wires) rectangle plug. It was the only other wire that went into the old stock radio. I tryed to hook my new radio speaker wires up to any of the 8 with no response. So, Where are the car's speaker wires? I have been wrenching for years but this is a new one for me!

Thanks,
Skid