The Shure V15 V with a Jico SAS/B stylus VS The Soundsmith Hyperion MR and Lyra Atlas SL

@mijostyn

"Now, what you are talking about is a co-axial point source which has absolutely no advantage over non co-axial point source speakers that are spaced closely together until you are a foot from the loudspeaker."

I beg to differ.  Where did the foot come from?  Whenever two separated sources play the same frequency (eg in cross-over regions) there is reinforcement and cancellation interference, as explained and animated here Discover the Surprising Flaw in Center Channel Speakers (youtube.com).

"In doing the variable diameter point source Quad was trying to improve dispersion characteristics at high frequencies"

The diameter does not vary - it is fixed by the speed of sound as it radiates from a virtual point.  Mind you, the stators are only static in the mechanical sense.  Electrically they carry the varying signal.  The moving membrane confusingly carries a static electrical charge.  I think one of the problems Quad tried to address was the cancellation and reinforcement interference experienced from different parts of a large panel.  They deliberately reduced the high frequency dispersion pattern, in ways I do not understand but probably in the delay circuitry.

"My assessment of modern Quads is there are dynamic speakers that outperform them in many ways resulting in a better listening experience particularly at levels above 85 dB"

Agreed.  I prefer my KEF Reference 1 at high levels.  These look like a two way speaker, but have two concentric drivers handling mid and upper frequencies.  Modern recordings seem to have more high-level transients, which trip the Quad protection circuits!

THIS is the dipole/planar loudspeaker I find myself lusting to hear. At $17,000/pr I can’t buy them, so it’s purely academic.

https://youtu.be/KQh66jM7aLE?si=ia3J7sKU7Eh9Z-MT

@bdp24 Interesting speaker with a few obvious problems. The tweeter is too wide which will cut down on it's horizontal dispersion at very high frequencies, the space in the middle is also a problem and the tweeter is not long enough, it will beam vertically. The Magnepan tweeter is a much better design. Like you I would like to hear them. 

@richardbrand you need to learn more about speaker design. The foot comes from the wavelength at the crossover point. If two drivers are closer together than 1/2 the wavelength at the crossover frequency they function acoustically as one driver. Woofers can be farther apart than midrange drivers and midrange drivers can be farther apart than tweeters. Tweeters have to be very close together which is the major problem for speakers trying to make line sources with stacked drivers. What you are succumbing to is lay assumption and as we all know assumptions are the mother of all f-ups.   Quad was trying to improve dispersion. Stick with your KEFs

@lewm Actually, I think they are $45 K now. I can say definitively that bi amping the transformers does not work. It is impossible to keep the amps from interfering with each other. I tried every permutation.

Our OTLs do a fine job of driving these speakers particularly in the midbass and midrange. They are not so hot in the treble. Because of the high output impedance the treble starts rolling off at best at 12 kHz. I know because I have measured it. On the bright side most older guys can't hear up there anyway. Solid state amps are more prone to having difficulty in the very low bass due to the high impedance of the speakers down there, but they go easily up to 20 kHz. The solution to this problem is to use a VERY big solid state amp. The JC 1+ does a fine job of driving these speakers as long as you keep the impedance of the interface up above 2 ohms. The Bricasti M28s also do a fine job. It is entirely possible that I might be selling my MA 2s. I have not made up my mind yet.