Those crazy guys at Autosound 2000 Ranch have one hell of an inferiority complex (and potentially the biggest subwoofer ever built). A couple of facts about it…from Clark - Navone with 60 Inch Woofer

The cone moves 6 inches peak to peak under full-tilt output. The actual cone diameter is 54 inches, with the 3 inch wide surround on the outside of that. The radiating surface area is 2,290 square inches. That yields a one way displacement of 6,871 cubic inches. That is equivalent to the displacement of 161 ten inch woofers that move 1.5 inches peak to peak. The motor is capable of producing 6,000 pounds of linear force, which is necessary when considering the very large surface area and displacement volume required to produce high SPL levels. The woofer was designed with the capability to produce SPL levels of 188 dB, which are entirely possible, given an appropriately built vehicle. It is simply a matter of displacement and containment.

Update - more pics from inside the van.

HUH…WHAT WAS THAT YOU SAID!?! FFF