[Micah D. Cranman]

Originally Posted by Technic

Again, if your standard system is the Stereo then you should disconnect the woofers from the mid and then add the tweeters.

This has to be done anyways for two reasons, impedance and to make the woofers sound the best with what you got. They should have their own amplifier channel so each can be tuned/crossovered more efficiently. There is no filter or crossover between the woofer and the mid with the iDrive system, so the sound is just split (highs/mids/lows) by each speaker own frequency response and that's it.

Agreed that this is the best approach if adding an aftermarket amplifier, but not necessary otherwise (i.e. running off the built-in amp in the head / iDrive / etc.)