While not sporting the biggest drivers in the world, the Velodyne 1812 is probably the most advanced. The name 1812 refers to the 18" bottom driver and the 12" top driver making it, as far as I know, the only true 2-way subwoofer in the world (the Bladder Buster's second driver is passive). The concept is the 18" driver handles the deepest of the deep while the 12" takes the sub's response up to 120Hz.

The Velodyne 1812 also uses the incredible Digital Drive room correction system. The way Digital Drive works is you hook up a TV to the sub, connect a microphone, and the sub pumps out a series of notes in various frequencies. Using the visuals on the TV, you can see your room's bass peaks and valleys and then correct them using the digital equalizer. In the end, your bass is perfectly tailored to your room, solving probably the biggest room/speaker issue in all of audio.

Spec wise, the 1812 is listed at 15-120Hz and can put out a massive 101dB at 16Hz. A single 1250 watt amp drives each woofer. Size is 40" high, 25.5" wide and 18.5" deep and 385lbs. Price is $15k.