I recently installed a new HU and found something i've never seen before. First of all i have a 1992 bmw 318 conv. with 6 speakers (two fronts work off one wire) and a factory amp with crossovers built into it. If anybody can help me bypass the amp later, i would appreciate it. Now i built my wiring diagram by trial and error and found that only the negatives are needed to put a signal to the speakers. when i touch the positive, the whole system cuts off.