C A R A U D I O
The 328 set comes with a slightly adjustable passive crossover network, passive meaning that it comes after the source of amplification and works at a higher voltage than the electronic one. It's very slightly adjustable, in that the tweeters can be set to high or low, potentially making the sound brighter than the normal setting. The crossover has a 12db per octave crossover slope, give the tweeters all frequencies above 4khz, midrange 250hz - 4khz and the woofer 120hz upto 250hz. As this crossover was custom built for these speakers, it works very well with the set, but it's possible to upgrade to MB Quarts MUSiCOMP crossovers. These are of a must higher quality designed without compromise using the best quality components, and aimed towards the competition and very high end audio market, possibly and expensive but rewarding upgrade.
Due to the installation limitations within the front of the E30 3-series BMW, the speakers had to be seperated. The resulting placement of speakers has meant that the tweeter and midrange speakers are in the kick panels, filling the cars standard front speaker position. This was very tricky, as the standard speaker size is 5.25inch and a 4inch and 0.75inch don't fit into this space very well. Also the standard location points the speakers right into the drivers feet, not an ideal situation for sound quality. The 6.5inch woofer was placed in the door panel, built into a custom made door panel. I hope to add full details of the installation of this speaker set as soon as possible. The tech. spec. with all the t/s parameters are below.
There is currently no rear-fill but I'm investigating the possibility of adding some, when I find time to test a few different setups. The most likely result will be the rear channel from the electronic crossover running a small Alpine amplifier, which will power the standard rear BMW speakers. This will probably to crossed over in a band-pass setup so as to produce only a mid-range output which will create only rear ambience and not interfere with the front stage.