[beanbaguk]

Originally Posted by Lancelot

I kept the focal crossover, using something else would require additional wires that the harness doesn't have:

Basically the bimmertech amp takes the 4 channels from the head unit, amplifies them and sends them back into the original BMW wiring going to the subs first then to the doors. This uses the first four A, B, C, D channels.

It then has 4 more channels available (E, F, G, H), the harness provides additional dedicated wiring for the subswoofers (E,F) + 1 center channel (G); Channel H is not wired. Technically you could probably run G and H channels to the front tweeters and setup the DSP to do the crossover internally, but it's going to require additional work from you, not sure the result is worth it.

I thought it was 6 channels with the base stereo?

2x Front mid-range + tweeters
2x Rear mid-range
2x Under-seat subs