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More Stereo Dribble

FWIW - the factory head unit in my '83  E28 was BMW mfg. by  Alpine.  It too
lacked adequite bass.   I suspect that the following may still apply  as many
newer model BMWs ( until perhaps very recently the HK units???) have factory
head units with similar limitations and manufacturer.  

 I ran a number of experiments, including driving the stock speakers (still
installed in the car) from a home stereo receiver temporarily wired to the
car.  A stereo installer had told me that the low frequency roll off of the
receiver was only 80Hz ( makes sense considering:
 1) the 4x6 speakers  and
 2) bass soaks up amplifier power, so to maximize volume level with limited
amplifier power, you curtail bass.

What I confirmed is that with wide bandwidth signal applied, the 4x6 speakers
sounded better than with the stock head unit.  I also got a copy of the
service data and specs for the head unit and was able to confirm that the bass
did indeed roll off at 80 Hz.

My solution was:  
o  New wide bandwidth Blaupunkt head unit,  o  Blaupunkt 4x20 watt amp, 
o  Blaupunkt 2 way plate speakers on rear deck, 
o  Pioneer 4" round speakers in the front kick panels to replace stock 4x6
(handled the power better and had better midrange (used 100 Hz cut off to
these speakers)
o  added factory tweeters on front doors by l&r side  rear view mirror
locations, and 
o  a 10" acustic suspension subwoofer in a custom enclosure in the trunk
firing through the rear seat w/dedicated 2x30 bridged amp with input from the
subwoofer channel of a graphic equalizer preamp.  

When I reinstalled the gear into an '86 528e, I left the stock speakers
intact, used the original factory wiring for the speakers where it terminated
at the stock amp in the trunk, and transfered everything except  speakers and
restored the stock system to the old car.

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