and this

http://www.bmwtips.com/tipsntricks/t...e%20review.htm

"Mike G" wrote in message
reenews.net...
Anyone with any specific suggestions for improving the OE system in an
E39?
Car has the 'Business HU' with cassette, and 6CD changer in the boot.
System has plenty of speakers, but IMO the OEM sound quality is poor.
Both treble and base seem weak, without any clarity or 'presence'
I'm not looking for a very good u/g, but if a reasonable improvement can
be made by simply replacing the main speakers front and rear with some
better spec ones, I reckon my limited knowlege of car audio could cope
with that. :-)
Any suggestions?
TIA.
Mike.