Electrostatic pros and cons.

I recently saw a feature on the program, "how it's made" on electrostatic speakers and it piqued my interest in them. I was wondering the pros and cons of them, their placement, space needs, sound, etc. Any advice would be appreciated.

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Apart from midrange transparency at which they excel, there's an overall coherence to an all electrostatic set up (not using dynamic speakers for woofers), but my experience is no doubt dated. I bought my first pair of original Quad ESLs (a/k/a the '57) in 1973 and ran them in various configurations, with subs, ribbon tweets and unadorned, until about 1990, when I bought a pair of Crosby modified Quad '63s- a better overall speaker with less beamy high frequencies, more apparent bass and the ability to play louder. But, to my ears, those '63s- which had the benefit of the Crosby tweaks from the era- never achieved that see through quality of the original '57, so when I decided to restore a set, I chose to have the '57s refurbished, not the '63s.
Over the years, I've listened to others (also dated)- Dayton Wright, some huge Martin Logan (I think it might have been called a Monolith but could be wrong) driven by Jadis amps at a lovely little boutique on the Il St Louis in Paris, their early, original CLS, and going back further, double KLH 9s with Marantz tube electronics, Janzen tweeter arrays, etc. I did not hear the Soundlabs- I should, nor the Beveridge, from back in the day. I gather that the Sanders are a preferred maker these days. 
I hung in with electrostats until 2006, when i switched to a horn array, one that also depends on dynamic woofers-- the Avantgarde. In some ways, a very similar experience in getting the deeper bass to cohere with an unfettered midrange. I keep the restored Quads as part of a second vintage system that is just "yummy"- perhaps a bit romantic, but oh, those old Quads- maybe I'm just lost in a nostalgic sound. The folks with the Soundlabs and Sanders might tell you that you can have it all without the shortcomings. 
Interestingly, on amps, I long ran mid-power ARC amps- high quality in the day, from a Dual 75a, to a D70 mk ii, to a Classic 60 (which was part of the newer ARC sound at the time- less tubelike). The best the old Quads have sounded, though, is with the measly old pair of Quad II amps running real NOS GEC KT 66s. Within the limits of that speaker, it's the best sound I have obtained on them. 
Electrostats can be addictive, even if other speakers can do some things (bass thwack, high dB) better. FWIW, I didn't confine myself to chamber music, string quartets and small jazz combos. You can hear into the music at lower volume levels. I would guess that with the right current model, large enough panels, you can come pretty close to getting it all. And perhaps, with more modern woofer technology, you can enhance them effectively without the seams-- I now run the '57s unadorned, without any tricks, mods or augmentation. 
They are insensitive to side wall placement, want to be well away from the front wall (the wall behind the speaker) and at least with the Quad, were acutely sensitive to tiny adjustments in angle- no doubt due to the very beamy tweeter panel.  Mine are in a relatively small room. 
Viz: https://thevinylpress.com/a-tribute-to-quad/
Thank you , all, for your input. I am definitely curious about them and just might grab a pair to see for myself.  
Being an owner of ESL speakers for several years, and having used and reviewed others and these in many systems, I disagree with several of the generalities associated with ESL speakers. I do not find ESL inherently superior in terms of cleanness, clarity, definition, etc. In fact, in some respects they are poorer than the finer dynamic or hybrid dynamic speakers. 

ESL speakers can reveal a wonderful amount of information, however they do not reveal more information than other types of speakers. It is more so the type of information they reveal which is construed as "more". Dipole and line source speakers produce unique wave forms, and I believe that is mistakenly taken as more information. 

While the scale of ESL is typically superior to most dynamic speakers, the resolution and fine detail of the center/phantom image is not superior. It is splayed, and that is unavoidable due to the nature of the drivers. 

Bass is typically a weakness with large panels. Some manufacturers do better than others in that regard. Declarations of one brand as inherently superior to others are highly subjective, and in my case not supported by actual use. 

I do not agree that they are superior in midrange transparency. I can get equally fine midrange from all sorts of speakers, line source, dynamic, hybrid dynamic. The character of the midrange, as with all frequencies is different with ESL. I am unwilling to give up LF in using an ESL speaker, and then try to compensate by saying the midrange is so great. That is simply not true in my experience. No one should buy an ESL because they think the midrange will be vastly superior. 

I do not agree that they are insensitive to side wall placement; placing material to their side along the wall has an audible impact on the sound, and I recommend people experiment with that. 

ESL can be a fantastic listening experience - or else I wouldn't own one. But, it has inherent weaknesses, and is not wholesale superior to other genres of speakers. Anyone who tells you so is speaking from emotion, not fact. 

I am not interested in debating or arguing my perspective. 
If tech talk is off the table, that's all I have to offer.

@audiokinesis: I think the technical aspect of the ESL is quite important.

The Beveridge lens revolutionized how ESL's sound, especially as it applies to sound dispersement and I'm not sure anyone realizes this but per Roger Modjeski who worked for Beveridge, Harold Beveridge designed these speakers to be placed on the side walls (Duke - recall that RMAF show where the room I was working had the speakers on the side walls - that guy whose name now escapes me worked for Beveridge too and copied the concept using dynamic drivers). The early Janzsen ESLs were also quite unique and the Soundlabs speak for themselves.

Having learned a thing or two from Bev, Roger Modjeski designed his ESLs to have uniform sound dispersement, without curving the panels. In addition, he realized the inherent weakness was in the bass and designed his speakers to be bi-amped with dynamic woofers which he selected to work best at 100 Hz and below. We modified a set of my Acoustat Model 2's using one of his panels (actually a half size version) to go along with the stock panel. I use a 4 box woofer array along with the Beveridge RM-3 crossover to filter the highs and lows at 100 Hz (4th Linkwitz-Riley 24 dB slope with a unique passive EQ added by Roger on the low pass board).

The other major tech improvement we made to the Acoustat's was removing the interfaces. Inherently, Roger felt the step up transformer is the real issue with ESLs. Anyone who hasn't heard an ESL with direct drive amps hasn't really heard what they are capable of. I'm working on taking my ESL 57s in that direction as well. As an aside, and from my perspective I do think the ESL 57 is still the standard by which any ESL is judged (it's what Roger Modjeski used as the model for his ESL), especially when it comes to the mid-range, but I also think people underestimate the bass in that speaker.
Bill, I like your room. Why do you have Avant Garde Duo and not Trio, by the way ? Too big or not much of a difference ?
Coherence is so important.