This owners manual has a good wiring diagram in it:

https://www.audiotec-fischer.de/en/m...ifiers/up-7bmw

I installed their 8" plug and play subs https://www.audiotec-fischer.de/en/m...kers/mw-8bmw-d under my seats. Dramatically improved sound. In fact, I had to go back in and put Dynamat under the passenger seat sub, because the sub was literally making the sheet metal vibrate.