Electrostatics and tubes

 The Link shows a variety of info relevant to the Quad ESL Development.

At the end in the Red Highlight, there is a reference to EAR having a Amp Design to be coupled as a Direct Drive. I have heard the Public Demo' of these in the 90's and from that day on, ended a search for a Speaker. The experience is one of the most indelible for being extremely impressive, I have had during my long term interest in using Audio Equipment 

I am a original 57 user and this evolved into using a Stacked Pair of rebuilt 57 models using One Thing Audio replacement Treble Panels.

I also as a result of the impression made by EAR, had Monoblocks Power Amps, Designed / Commission Built using 845 Tubes and Hand Wound Transformers to drive the 57's. 

I am also very Familiar with Quad ESL's owned by other, being 57's and stacked 57's,  the 63 model from different era periods of production, through to the 2912.

The 57's in a Good Condition !!, hold their own in all Quad ESL Company.

Early production 63, built as the first 200 Models has been used in demo's against 57's ,a later model  63 and 2912's, where the early production 63, has stood out as attractive in use as the 57 and 2912, this is a very difficult find, leaving the early and later Quad Models as the easier options to acquire.

Later model 63's in my experience of the ones demo'd, are enjoyable when encountered in use, but when used as part of a demo' comparison to earlier / later Quad ESL Models, the later model 63's I am familiar with are shown to be wanting more of an improved end sound to compete.

The 57's and 2912's are used in different systems regularly listened to. As systems, these have also been used to add other types of audio devices to for demo' purposes.

Whether the 57's and 2912's are being used with a different Source, Analogue Digital, Pre Amp Design as SS or Valve, Power Amp's as a SS or Valve. The 57's 2912's are always able to offer an impressive end sound, as well as easily be able to produce a sonic difference to help evaluate a change being made with a Systems devices.

https://www.quad-hifi.info/public/esl57%5B3015%5D.pdf

The subject of Sub’s used with Quad ESL’s or a Tweeter to extend the upper frequency on 57’s is a widely discussed subject.

I have experienced Sub’s in use with a variety of Quad Models and a Super Tweeter in use with 57’s.

From a personal preference I find the additional Tweeter adds something that really appeals to me, ands would like to hear a Tweeter added as a Dipole Array to lift the higher frequencies.

I have detected on occasions that a added Bass is in use, from the experiences had, there does not seem to be the seamless integration into the produced end sound when the Bass is an added as a design being a typical Bass Driver set up. I am yet to experience a Dipole Array for Bass Drive Units being used.

Additionally, I have heard 57’s used with purpose produced Power Amplification that has been able to create the impression there is substantial Bass presentation , and the idea more lower frequency is required seems fleeting as an idea to be realised. I have even experienced others who have been demo'd such a set up, where some listeners have inquired which Sub Woofer is in use?