[bmw325i]

Originally Posted by ctuna

Read these this will give you most all the info available .
There are block diagrams of the wiring and specs.
Most people do not leave the stock amp in with a Hi Fi upgrade.
10th link is Hi Fi block diagram.

BMW stereo types
http://www.e90post.com/forums/showthread.php?t=352586
http://www.e90post.com/forums/attach...2&d=1266451970
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/showthread.php?t=343673
http://www.e90post.com/forums/showthread.php?t=138949
http://www.e90post.com/forums/attach...2&d=1260829447
http://www.e90post.com/forums/attach...1&d=1209780605
http://www.e90post.com/forums/showthread.php?t=641323
http://bmwcoders.com/forum/3-er-8/bm...1-e92-e93-291/
http://www.e90post.com/forums/attach...1&d=1209780865
http://www.bawarec.ru/manuals/3er/e9...3er-e90-12.pdf
http://www.musicarnw.com/page-2/
http://www.e90post.com/forums/attach...4&d=1278871872

Yes the rears are connected. The stock speakers are 2 ohm . This means whatever amp you use must be 2 ohm stable and will output wattage at the
2 ohm spec. Doesn't matter that much if you use 2 ohm or 4 ohm for an aftermarket amp with decent power . However the stock speakers are not really designed for aftermarket power , do people leave them in and not upgrade them , yes

His rear speakers now are 4 ohm (hifi). The logic 7 speakers he is putting in are 2 ohm. Another reason why the rear speakers can't be powered with the stock amp.