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

My First Experience of 57's in use was in the 90's probably early 90's when Tim De Paravicini demonstrated Valve Direst Driven Quads at a Audio Event I was attending at, from recollection be music being used was Pink Floyd - Pulse - Master Tape.

Being Blown Away was an understatement.

I also heard them in use by another enthusiast when I was a user of both Single and Stacked array's, (I've never really prejudiced against the Single Array). The enthusiast was a Quad Obsessed Type with experiences acquired for 57's and also had good electronic skills. Panels were Overhauled and the used panels were matched to 0.5dB from recollection. The Stacked Quad enthusiast visited was owning a Pair produced to their design, completely stripped down and rebuilt using only one set of Electronics to Drive the Speaker Design. 

Thus single electronics design, was built into a extremely rigid structure, using Black Walnut as the Framing, these really shone as a Speaker. The Source and Amplification was poor for what a Quad ESL 57 really deserves, but this speaker design really shone for its capability.

My Gut Instinct is that the Typical Stacked Array will have been noticeably bettered by the new design for the Stacked Array heard. Especially with a improved Source and Amplification.  This is also a design I would really enjoy putting together as a retirement project, where I would be reliant on a EE friend who renovates 57's. Getting the Panels matched to 0.5dB will for me not be something achieved unless having luck with me.

As for the Super Tweeter, I have heard the Super Tweeter from Townsend in use with 57's, but can not recall anything really memorable and requiring to be wanted to be reproduced, but maybe that is because I never heard them coupled as a A/B demo with them cut out and on use, as I have had demo's with quite few Subwoofers I have heard coupled to the Speakers.

As for the High Frequency / Low Frequency Driver Designs to be attached to the Quad ESL 57.

My own intention is to one day have a Audax Gold Dome Piezo HD-3P Tweeter coupled to the 57's. This Driver is one which I and friend have collected samples and devised methods for refurbing the and re-charging the reservoir. This is then enabling the Driver to become very usable for long periods of time, longer that the design from the Manufacturer. My take and my friends take, is that these might be one of the best Upper Frequency Drivers ever produced for the end sonic they are able to deliver. The Driver produces sound by stretching the Gold Coated Diaphragm, which is very much a design to be coupled with a Film that produces an energy to be converted to sound. The Subwoofer choice is a Ripole Design, just to see how a figure of eight radiation will blend with the 57's figure of eight radiation pattern. 

My friend who refurb's the ESL 57's has chosen their own was of assembling an array when they take their 57's out to be publicly demonstrated, the Speakers are reorientated to have the Panels Treble and Bass Panels longest sides placed on the Horizontal. The Speakers are usually Spread across an are of approx' 16 feet.

My Amp's had Tranx's specifically wound with the 845 Valve to be used to Drive the Quad ESL 57. When out at shows doing Public Demo's of my Audio System, the most common asked Question is about the Subwoofer I have selected to be used with the Subwoofer. Quite strange facial expressions are seen when informing there is not a Subwoofer. On one occasion, a Show was local to one of the UK's most renowned overhaulers of the ESL 57. A show attendee who new the Company owner personally contacted the owner, encouraging them to attend and listen to my Quads. I was told this during the latter part of the show on Day 2. The Company owner did attend, but did not introduce themselves, so I didn't get the chance to inquire about their own impression of the set up.

Quads with the correct approach can present Bass Just Fine, I learnt that in the room with TDP and the Valve Direct Driven Design. For my purposes, my own design for them produces and end sound and Bass very similar to what TDP had achieved, my recollections used many many years ago reassured myself of this. In the modern day, when I introduce my owned Three Way Floor Standing Cabinet Speakers into the System, the only Bass Issue is the Cabinet Bass and Panel Bass are noticeable for their differences, but not the extension differences that might be different for each Speaker Type. 

Recently I have heard a Cabinet Speaker in a friends system, that I believe would easily trounce the ESL 57, I could even buy into the Design as it is a Troels Gravesen design for a Speaker. Interesting one this one, as I recently learnt that Troels has seemingly used Quad ESL's and EAR Amp's designed by TDP  to learn about how a Speaker can be Voiced.     

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.