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

Wow, this is getting interesting!

Hopefully this is my last quote from Peter Walker of Quad on the subject of speakers: "Anybody can build an electrostatic loudspeaker.  The trick is to build one that lasts" or some such.  

In the 18 years between inventing and releasing the ESL-63 to the market, Peter built in many protections.  The most effective, in my opinion, is an incipient ionization detector that senses when sparking is about to occur.  Other measures include reducing the instantaneous signal voltage when it gets to 40-Volts and shutting it down at 56-Volts.

A very influential person in the modification space was the founder of SME, Alastair Robertson-Aikman,.who tried stacked ESL-63 speakers (stacked at right angles).  He beefed up the frames, and tilted the panel back slightly.  Quad made a beefed-up ESL-63 for studio use, and Robert's ideas found their way into subsequent Quads like the ESL-2905 which I use now.  Ironically, despite the massive weight bolted to the base, the standard floor spikes, the reinforced frame and the stressed triangulated support bar at the rear, the panels themselves still float in a foam surround.

My source, apart from general reading and personally meeting Peter Walker and pulling apart and rebuilding ESL-63 and ESL-2905 speakers, is the book by Ken Kessler which is included, along with white gloves, with each pair of ESL-2905 speakers.  The square wave test reportedly caused over half the production to be rejected.  Production has now moved from England to China, where much more attention is paid to details of assembly.  For example, every screw for the grills is also cemented, and every wire is hot-melt glued wherever it traverses a slot in the panel frame.  The Chinese have not been as successful with the adhesive used to attach the mylar film, and most of my panels have needed repair over say 20 years There are 12 panels per pair.of 2905, 8 for 63s.

The Finnish company Gradient made ob/dipole subs for both the QUAD ESL and QUAD 63 back in the 1980’s/90’s, but they were not built to perfectionist standards. They were somewhat similar to the ob/dipole woofer system Siegfried Linkwitz used in his LX521 loudspeaker.

The OB/Dipole woofer system offered by GR Research in partnership with Rythmik Audio is similar, but of much higher quality and performance. Two or three (or more, your choice) 12" woofers (optimized for open baffle applications) installed in an H-frame (though the woofers may also be installed in an M/W frame, as Linkwitz did), with a Rythmik Audio plate amp that includes servo-feedback control of the woofers, along with a dipole cancellation compensation circuit. THE woofer to use if you want to add subs to your QUADS.

@bdp24 Dipole subs do not work well, I have built and tested them. No matter how heavy you make them they shake and the cancellation effects along with room modes create wild frequency response aberrations.  The problem for line source users is to match the radiation pattern of a line source with a subwoofer system. Using the same math above subwoofer drivers need to be spaced less than 1/2 the wavelength of the highest frequency they are to reproduce and the array has at end at barriers, either side walls or floor and ceiling. I chose side walls for my system using 8 drivers to cover a 16 foot wall. 

@pindac 57s hate making bass. They will do it at the expense of reliability and Doppler distortion. One of the reasons we were blowing 57s all the time with the HQD system was the crossover point to the woofers was too low. The problem was we only had slow analog active crossovers in the day and even John Curl can't work miracles. The HQD system was driven by all Mark Levinson equipment. With digital crossovers you can run much steeper slopes bringing the crossover point up as high as 100 Hz while still keeping the subwoofers out of the midrange. Given the System you have you really should look at the DEQX Pre 8. It is a digital preamp with a fully programmable 4 way digital crossover. It is a DIY speaker maker's dream. https://www.deqx.com/ The are still selling Beta units at 1/2 price.

@richardbrand The first indestructible ESL was the early Acoustat series, not their amp, just the ESL panels. Then there is the Sound Labs which are totally indestructible. I have tried desperately to kill these speakers and the only things I succeeded in killing were two JC 1 amplifiers and two bass transformers. You can turn up the bias supply and "spark" the diaphragms without any damage whatsoever. I have no experience with later Quads as none of them meet my specification being point source speakers. You can stack them but they still will not become a line source as the active part of the elements is too far away. Peter Walker is a plagiarist. He essentially copied Edward Kellogg's 1929 design, an American working for GE. Arthur Janszen patented the first ESL design in 1955 two years before the 57. Arthur also designed the KLH 9 in 1957 arguably a better design than the Quad, but very large and hard on amplifiers. By itself the Quad 57 is a midrange driver for apartment dwellers. To obtain a reasonable output suggestive of a live performance an ESL must be a line source and be crossed over to subwoofers. This leave us with the Dayton Wrights which take second place for the worst speaker design ever. First place goes to the Hill Plasmatronics. 

There is something about the Shure V15 V that I do not like. I have not put my finger on it yet. I have to make recordings of the same records with various cartridges for AB purposes. 

Like I said, in my opinion Quad 57s are best if you remove the complex electronics that Walker implements in order to make the panel act like a point source. Then a stacked pair (or triplet) can act like a line source. Hearing is believing. 

Dear @harpo75  : " Sold the Thorens and bought a Micro Seiki BL-99V turntable, put a Technics EPA-100mk2 tonearm on it and I alternate between my Technics EPC-205 mkIV Jico SAS and a EPC-100mk3 original stylus.  I also have a Pickering XSV-4000 w/original stylus that sounds wonderful and full and images better then the Shure did.  Both Technics have more detail and air, image, speed.  "

You arejust rigthand that's because the Shure V15 V MR was and is part of the vintage MM cartridge mediocrity/average not a very good performer where exist several MM and MI vintage cartridges way superior. Shure is an inferior cartridge.

R.