The new sub from Zu cable is called the Retro. It is passive, and comes with an outboard parametric EQ from DBX PRO. The DBX PRO box is from the parent company we all know as Harmon International, so you know the blood lines.
The Sub is a large 15" driver and is 93 DB efficient. I am driving it with only an extra 85 watt channel from my Carver AV-505 5 Ch. AMP. This is more than enough to shake the pictures on the walls, but gentle enough to be clean and fast for excellent music. This sub has replaced a Velodyne FSR-15, and has put it to shame in all categories. The cool thing about the sub is that you can tweak all of the EQ and crossover settings with a computer while you are listening. The DBX PRO has 99 presets so you can literally make multiple setting for different listening scenarios.
The Sub is going to be officially released early this summer, I was fortunate enough to aquire one early. the one I got was used at CES.
see this link for a photo http://www.audiocircle.com/circles/viewtopic.php?t=650&start=10