Yes, I have. I heard them many moons ago. I did extended auditions of them at a loose end in Phoenix and Portland Oregon.
They were very similar to Electrostatic panels, with all of their strengths and problems and an additional one.
They beamed, and were spl restricted to a degree.
There was one additional problem. The wags used to say, "You need a smoker amp, and when the smoke escaped it was over!" The impedance was one ohm. So people tried transformers, and above all 1 or 2 ohm resistors mounted on heat sinks.
Bob Carver had a hybrid ribbon, that crossed at 100 Hz. One of our cardiologists has a set of those, in fact a number of iterations over the years. One set was delivered personally by Bob Carver, and that was when he got to hear my monitor TLs in my Grand Forks studio. These speakers are now my rear backs.
Bob had the same problem as Martin Logan.
A planar speaker is a line source, and spl reduces 3db for every doubling of distance. A moving coil driver is a point source and spl reduces 6 db for every doubling of distance. Add to that one is a monopole, but at the operating range we are talking here, a full space radiator. A panel like and electrostatic, ribbon or magneto planar like Magnepan are di-poles with figure of eight radiation pattern.
So integration is impossible. Franky I disliked Bobs speakers nearly as much as the hybrid Martin Logans. They are worse because the crossover is higher. This issue applies to sub integration also. This is why the Gradient sub was developed for the Quads.
We have a thread going about a Funk line array. I have not yet dared ask how you integrate that seamlessly with a sub.
As you well know a perfectly balanced integrated bass is a rarity.
