I will be doing the installation in baby steps. First thing I did today was to add a tweeter to the center channel since JBL highly recommends a full range center channel. I shamelessly stole one of the rear deck tweets out of my old car (330i w/ L7) and installed it in the air duct just to the left of the midrange driver. Even though the L7 tweeters are relatively low profile, there was no way to mount it above the mid as there was just not enough space. The L7 tweeter plugs right into the center mid so the wiring was plug and play. When I was done I turned on the radio and made an interesting observation: it sounded freaking good! The imaging had improved significantly! Voices were now almost centered above the steering wheel, at least 10" over to the right and a couple of inches up as well, compared to where they were before. I was able to return the balance to the center position (was at +2) without pulling the image to the left. It also sounded more crisp, which was to be expected of course. I can honestly say that adding that one tweeter turned a mediocre sounding front stage into a very good one. We'll see if the MS-8 can take this "optimized" 14 speaker L7 system yet to another level...
Pics of center channel tweeter upgrade:
L7 tweeter with in-line crossover and plug-in connector
Tweeter plugs right into midrange
Tweeter mounted using high-tech bracket made from tin cookie box
Gorilla glue is awesome