I have an ancient Pioneer head unit that only has 3 speaker wires. It's an old Jeep requiring a shaft-mount stereo (mounted by the knob shafts), and I don't want to cut the dash for a DIN. There's +L and +R, but only one negative wire out of it. You're supposed to wire the negative to one speaker, then jump that terminal to the other speaker's negative. Obviously the LOC has 4 wires. I tried twisting the two negatives together on the LOC to the single ground on the stereo, but there was only sound from one speaker. I have a feeling I might be screwed. Anyone know how to deal with this?