Quad ESL 57 with subwoofer

Thanks Dynalead. So are you running them from the same amp in parallel with the ESLs? I was thinking of powered sub(s) using a high impedance input from the speaker terminals...

I had a DIY sub with quad 57s with passive x-over but just between you and me the bass quality was better without the sub after removing the metal grills.

The best sub for any dipole is an OB. In the 70's a company named Gradient made one for the ESL63, with two 12 inch drivers facing in opposite directions in an OB "H-frame". A company named GR Research now offers a similar design, but with the addition of the Rythmik Servo-Feedback system. It is available only as a DIY kit, which is two 12 inch drivers and one 370 watt Servo Amplifier. You build (or have built, from the plans on the GR site) an H-frame into which the drivers are mounted. Serious, world-class bass the blends really well with dipole speakers. A pair will cost you about $1500 plus the cost of the H-frames.

Thanks all. Good stuff.