[surayne]

These have recently been released by Audiotech Fischer:

http://www.audiotec-fischer.de/lng/e...mw-8bmw-d.html

Anyone have experience of these? They seem to have an interesting design - 2 voice coils that can be amped separately to provide a better frequency response, quoted at 25-140Hz. They're designed as drop-off replacements for all BMWs with underseat woofers.

[Billfitz]

Originally Posted by surayne

2 voice coils that can be amped separately to provide a better frequency response

Dual coils don't give better frequency response. They're typically used to offer more than one impedance option for better matching to the amp.
I wouldn't count on these working any better than stock. The claimed 25Hz low end is a fantasy, even their own spec sheets recommend a 40Hz high pass. As for maximum output, that's determined by the driver cone maximum excursion, T/S spec xmax. That's 4mm, which is marginal. A good 8 inch sub will have at least twice that. I don't know what the stock driver xmax is, but I can't imagine it's less than 4mm, and it's probably more.