Illusion Audio has started shipping a new version of the Carbon C8 Midbass Driver.
https://www.dowelectronics.com/illus...iver-each-c8-w
I had planned on using Jenhert XE200 8” drivers for my under-seat upgrade but they are no longer available, at least in the USA.
My searches kept coming up with the Audio Development W800NEO and the Illusion Audio C8 as top performers, even though I could find few examples in BMWs' under-seat location other than JimmyDee's W800NEO. As luck would have it a new version of the C8 was just released and arrived the day I dropped my car off for installation. I don't have the specifications but understand both the flange and depth are about 1/4" smaller. The basket is different and the mounting holes are no longer recessed. They have also configured the binding posts inside the basket so they don't add depth to the installation.
Musicar Northwest crafted a beautiful adapter ring and dropped it in and I have a few hours of listening so far. Hard for me to tell how the C8 is performing since it is now tuned as part of an 8-speaker front stage, plus the rear stage and subwoofer, but overall the system sounds fantastic.