A little background. I replaced the B&O sub in my 2011 S4 with this pioneer:

https://www.pioneerelectronics.com/P...S-W260D4#specs

Highlights:
-Dual 4 ohm voice coils (meant it could be wired in series to match the 8 ohm B&O impedance.
-Worked in Free Air applications
-93 db sensitivity!

Well, I just traded in my S4 on a used S6, and I've already replaced the 8" sub with a Polk, and that's not cutting it. Had I known that this Pioneer was no longer available, I would have ripped it out before I traded in the S4. The new version of that Pioneer can't be used in Free Air applications.

So now I'm on a grail quest for a Free Air 10" with 4 ohm DVC and a high sensitivity rating. Dammit I should have kept that sub. It's looking like a unicorn these days. I should mention that I'm looking for these specs because I'm just trying to match a sub with the existing B&O equipment.