Originally Posted by DeFKnoL
Technic, you have made my day!
I'll be anxious to know when you've done that harness for the back of the iDrive unit. Also, do you know off hand if there are line-level outputs on that or are they just the amplified ones going to the speakers?
The iDrive outputs 25W x 4 (@2 ohms), not flat (OEM pre-EQ) signal, full range in the front outputs and high pass at around 100Hz in the rear outputs.
Therefore this signal is quite cumbersome to work with if you do not plan to use any summing and de-EQ processor before an aftermarket amp. You could, but as you can see you will have a couple of sound quality issues if you use the OEM outputs thru just a line level converter into an amplifier without any processing. In other words, you will be just amplifying whatever the OEM EQ curve is -which is mostly designed to match OEM speaker characteristics and not sound quality itself, after all there are no tweeters in your system. That should tell you something about this signal EQ.
There are some devices that can help you to "fix" this signal and even set your own EQ/time delay processing, all depends of your budget and plans.