A Quad Sub Tower that didn't perform as expected.
One of the problems with using Electrostatic (ESL) speakers is that its tough to add a subwoofer and make a seemless transition between to do because of the ESL's being so "fast" and resonance free. Also my ESL's only go down to 200hz which is to high to crossover to a large woofer with good results. Crossing them over to a large cube subwoofer just doesn't work well. At first I decided to use 4 - 12 inch drivers per side custom made with a Hi "Q" so they can operate on an open free air baffle to eliminate most cabinet resonance problems. Because of wrap around cancellation much energy is lost and it takes 8 drivers to get a good SPL level.
Update: I built these and they didn't work as well as I planned so I scrapped them. Even with 8 - 12 inch woofers total the wrap around cancellation was to much for them and they bottomed out much to easily. I am now in the process of building 2 midbass towers that are each 8 foot tall and contain 8 - 5.25 inch Dayton woofers each in their own ported 0.59 cf partition. They will go down to about 48 hz and should be light enough and fast and loud enough to keep up with the ESL's. I will be using a Carver TFM 45 and a Richter Scale active crossover/equalizer with these. I will post pictures and results when I get further along with them.