I put t-taps on my rear deck woofers in my 2000 BMW 323i and connected them to wires which had rca jacks on them question is I think i may have the combination wrong I did Left deck + and right deck + to red rca wire and left deck - and right deck - to black rca wire.. it sounds weird because if I remove the black one from my amp it sounds like bass but when its connected it just looks like the subs are moving with no bass
only reason i thought i could do that is because my friend has it on his car and it works mint... I picked up a LOC this morning and it works great thanks
I'm guessing you're friend probably has a stock amplifier in the system, and tapped the wires BEFORE the amp. That's the only way that could possibly work.
Or his amplifier has built in speaker level inputs, basically a built in LOC.