@pindac: No but using Tympani bass panels with Quads is a very interesting idea! The problem for me would be the required room size; the two Tympani bass panels are about 40 inches wide, the Quads about 34". Side-by-side the Tympani/Quad pairing requires just over 6 feet per channel! That 12 feet (for both channels) plus say 8 feet between left and right speakers requires 20 feet, and that’s with the Tympani/Quad pairing being right against the side walls.
In the 90’s I put my Quads on top of ESS Transtatics, the Transtatics laid on their sides (20" tall when so placed). I used the Transtatics as subs; they feature a transmissionline-loaded KEF B139 woofer (Dave Wilson used a pair of that woofer in each of his original 1970’s WAMM super speaker).
In the 80’s and 90’s the Finnish company Gradient offered dipole/open baffle subs designed specifically for both Quad 57’s and 63’s. Those subs also served as bases for their respective speakers. The dipole/open baffle sub now offered by GR Research and Rythmik Audio is a much improved version of the ob/dipole design, and work splendidly with all dipole/panel speakers, including of course Quads. My Quads are now in storage, as I am currently listening to Eminent Technology LFT-8b’s and LFT-4’s. The GRR/Rythmik OB/Dipole Sub may be used in place of the LFT-8b’s stock 8" sealed woofer; the LFT planar-magnetic driver plays down to 180Hz (crossing over to the 8" dynamic woofer), and while "normal" subs can typically play no higher than 100-120Hz, the GRR/Rythmik OB/Dipole woofer can be used up to 300Hz.