A 15 inch Sica-made DVC subwoofer -- it is (they are: two of them) enconsed in a prototype subwoofer that I acquired a few years back. One forward-facing, the other downward-facing.
I know nothing else about it (them), but the availability of four voice coils
in toto affords numerous wiring configurations to play with.
It was meant to be used with a plate amp and DSP. I bought the cheap "250 watt" PE Class D plate amp (with some rudimentary DSP) when it came out to use with it.
No complaints, but I have done very little exploration of its capabilities.

Pay no heed to the (
ahem) passive high level XO to the left, sitting on the EV Coronet enclosure

-- it was hooked to
something else entirely at the time the photo was taken and is irrelevant to the subwoofer.
The plate amp, FWIW:
Dayton Audio SPA250DSP 250W Subwoofer Plate Amplifier with DSPDayton Audio SPA250DSP Subwoofer Plate AmplifierElite Control with DSPDayton Audio's SPA250DSP true 250 watt digital switching plate amplifier features advanced signal processing control that every audio enthusiast wants. With Class D...
www.parts-express.com
Note my hand-crafted, artisanal enclosure for the amp

It's actually open-backed to help with airflow (but mostly due to some clearance obstacles.).