The biggest baddest sub woofer made.
The Parthenon. The ultimate loudspeaker driver. More excursion, more output, higher power handling than any driver on the face of the earth. A true 82mm one way linear stroke (nearly 6.5 inches peak to peak linear), and a radiating surface greater than three 18" subwoofers allows the Parthenon to generate the highest SPL levels ever achieved by a single driver (more output than eighteen high end 18" drivers)...

[Link: adireaudio.com]