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In Reply to: Re: Bye Bye BMW Sound posted by Harold on May 06, 2000 at 20:48:15:
All I have done is add the CD changer ordered via Pacific BMW, and added a separate 10" JBL sub woofer in a 0.75 cu ft. sealed enclosure. That is driven by a "240 watt" bridged Blaupunkt amplifier. By carefully setting the bass boost and amplifier gain, I can run the bass settings at the stock head unit at flat or -1 or -2 and get more than enough good clean tight bass. I find that this "untaxes" the stock amp and speakers from attempting to generate any real bass which thus reduces/eliminates the distortion and missing bass that so many have complained about.
As for mid range and high frequency response, I think that AM radio can't really generate any in the first place ( unless you go with a "wideband" IF circuit which 99% of ALL head units are NOT - although Blaupunkt made a unit {Tuscon ?} that had switchable IF bandwidth several years ago) and I suspect that the guys that designed this stock radio deliberately rolled off the high frequency response on FM to hide the hiss that marks poor reception when the signal strength is too low to produce full quieting in FM Stereo.
I find that the sound from good cassettes or from CDs to be quite satisfactory. Part of this, of course is what I listen to and how I listen to it. The cabin of the car is quiet enough that I don't really need to drive the amplifier to full power and hence, high distortion from the amp and speakers, to hear the music, and I am not into Bumpa Bumpa , thumpa booooom boooom sound that you hear two blocks away.
Among other problems with replacing the head unit already mentioned (wiring, speakers, and amplifiers) is the consideration of an antenna. BMW uses the rear window defroster grid to provide 4 separate antennas, each of which is electronically amplified, and then fed to the stock radio simultaneously. The radio then "continuously" compares the 4 antenna inputs and selects the one with the best signal at that moment ( the so called "diversity" antenna system) in an attempt to minimize multi-path distortion. Ever notice in most cars that if you are stopped and the radio (FM) sounds horrible, if you ease forward a tiny bit, the sound clears up ? By have multiple antennas in different positions/locations you can do the same thing by electronically switching antenna inputs until you get the best reception. Of course, it would be better if the were not all clustered on the rear window, but- - - . So given the above description of the stock antenna, you have to figure out how to adapt it to the new radio ( which typically is NOT designed for a diversity antenna input).
Other than what I have done, it's a tough and expensive proposition to make significant changes to the sound system in these cars.
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