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Quad  ESL-57 loudspeaker

From Hi-Fi World - October 2007 issue






One Thing Audio now offer an even better upgrade to Quad's original ESL-57 loudspeaker. Is this the electrostatic for you, wonders Noel Keywood?


As I waved my Tannoy Yorkminsters goodbye, tear in my eye, I was dreaming of my next affair. There’s always another, different experience around the corner. The notion of a perfect electrostatic was on my mind and, as if reading it from afar, a pair of revamped, tuned Quad ESL-57 electrostatic loudspeakers arrived in the office from One Thing Audio. The large spaces left by the outgoing Tannoys were promptly filled and my tears vanished...

The ESL-57 was Quad’s first ever electrostatic loudspeaker. Introduced in 1957, it is still popular today, retaining value as a classic. However, the ‘57 was always a little fragile and most around today, with a good forty years use under their belt, are barely working. One Thing provide a unique rebuild service for this loudspeaker: they equip it with new, improved panels, and revamp it to provide a level of performance considerably better than the original.

If you already have a pair of 57s, the upgrade costs an affordable and highly reasonable £1,450. To that, add £235 per pair for the Rupert wooden stands you see in our pictures, and £79.95 per pair for Widgets (yes, that’s their official name) that make the loudspeakers a friendlier load for transistor amps. You end up with a loudspeaker that’s not only a classic but, we have found from past experience, frighteningly good by today’s standards. Which is why I was dreaming of electrostatics again when the Tannoys went...


If you are wondering why the ESL-57 looks like a radiator - a common accusation - it’s because it is a panel loudspeaker. To be precise, each one uses three sheets of Clingfilm - or something like it in truth - to produce sound. One sheet, tensioned in a frame to form a panel, sits vertically at centre, radiating high frequencies. Either side of it are bass panels - hence the oblong proportions of the composite whole. The louvred metal covers let sound out, front and back, whilst preventing inquisitive little fingers from getting in, because lethal voltages exist inside; these speakers are mains powered.


I had a long talk with One Thing about what they do with the ESL-57 and its technology in general because, as you might imagine from someone who dreams about such things(!) I am more than a little interested. I did, after all, run ESL-63s for many years, modifying them heavily and finding there was always more to come.


One Thing can accept just about any ESL-57, irrespective of condition, and renovate it fully. If you don’t already own a pair, then they should cost around £400 per pair second hand, but having said that some ask for much more, up to £1,000. One Thing recommend people buy tatty ones cheap, as good ones are likely to be good looking rather than good sounding, and One Thing replace all important parts and can even fit new grilles. All you need to be aware of is that models predating 1960, with a Serial Number below 1200, are balanced for mono, having less treble energy due to fewer turns on the audio transformer’s high frequency secondary winding. So pairs should have similar Serial Numbers to avoid a pairing of old and new models, which sometimes happens, and which One Thing cannot rectify, as the audio transformers are different.


The ultra light film diaphragms of electrostatics follow musical waveforms with unnerving accuracy, magically banishing screechy violins caused by the wayward cones and dome tweeters of conventional box loudspeakers. The lighter the film, the less energy it stores to colour the sound, and the faster it accelerates and decelerates, to better follow the music. In this respect electrostatics are way ahead of cone loudspeakers, something that is audibly very apparent.


Whilst Quads and other electrostatics traditionally used difficult to obtain special DuPont films, One Thing went to Germany and ordered an industrial quantity of a specially manufactured film 2.8microns thick, compared to 6microns of the original. This is coated with a highly resistive conductive film so the surface holds charge, resisting charge migration. I was surprised to learn that One Thing also fit high voltage secondary protection circuits of the sort used in later ESL-63s, which from experience I know work well. So their upgraded ESL-57s are all but bullet proof, which is good to know because I remember the originals being prone to arcing when overdriven. Additionally, they fit improved front electrodes to better disperse mid and high frequencies, and stronger rear electrodes. All in all then, this is a very modern electrostatic, to the pattern of the original, but otherwise broadly updated. Only the audio transformer is retained.


Some solid-state amplifiers find electrostatics difficult to drive - meaning they blow up! Mindful of this, One Thing offer a Widget that makes the Quad an easier load (it is a reactive network, not just series resistance). This, they find, improves sound quality with solid state amplifiers. With valve amplifiers it has least affect, they told me. With the Almarro valve amplifier I used, it offered a small subjective improvement, adding just a little body to voices. All the same, with it or without it the ESL-57s sound bright in their balance, due to a +5dB lift at high frequencies our measurements show, which is quite a lot. I would be tempted to equalise them flat. One Thing said many listeners prefer this balance, and it does mimic the lift found in many modern loudspeakers. I am used to a ‘flat’, neutral balance that is gentler with DVD-A, which tends to sound brittle in any case; the 57s were also bright with much SACD, even though it has subtler treble than DVD-A, but they were better balanced with most LPs.


 I’m talking only tonal balance here. Transparency and insight are other important properties and here the ESL-57s were unmatchable. They see through everything, being brutally frank about recording quality and balance. As much as I enjoy old classics like Billy Idol’s 'White Wedding', or Steve Earle’s 'Copperhead Road', they sounded dated with these loudspeakers. The recordings were ill balanced or congested, the Quads told me. Yet at the same time, whilst limitations in recording quality were starkly revealed, I was fed Steve Earle and Billy Idol at the microphone like never before: fantastic!


Spinning a good, modern recording on DVD-A like Toy Matinee’s 'Turn it on Salvador', the extra resolution of 24bit at 96kHz was glaringly apparent. Instruments were sparkling clean, vocals starkly clear: what revelation! Where a big Tannoy brings lusty dynamics to all sources, the Quads perform analytical surgery on a scale unknown to most - loudspeakers or men that is! - laying bare both performances and the technology used to capture them.


These particular ESL-57s are about the most revealing loudspeakers I have ever heard, helped by the fact that they have been built with just that property in mind. The modifications One Thing make, such as a lighter diaphragm film, give subjective improvements that capitalise upon the loudspeakers intrinsic strengths, moving it even further ahead of the herd.

Quad ESL-57s do not have deep bass, nor a full bodied or warm sound. Being an open dipole, exactly what you get from them depends much upon the room and their positioning within it. In a suitable room I have heard 57s give bass of a quality, if not a power, far beyond any box loudspeaker, but this is rare. Basically, 57s peak up in the upper bass region (90Hz) and roll off below this point. You get a form of bass, but it has no great depth nor thunderous strength - at least, in my room. A subwoofer can help.


Quads benefit from having some space behind them, to ‘lose’ sound from the rear. This, and their size, mean that a largish room is best. Long narrow rooms measuring 20x12ft or thereabouts are ideal, with each panel end-on against or close to the side wall, facing down the room. Positioned like this the side walls augment bass from the panel and the rear wave is usefully attenuated. An alternative is to place absorptive panels a small distance behind each speaker, using acoustic foam or similar. Do not expect to place any open panel, including this one, flat against a wall, nor anywhere near it.


Remembering back to earlier Quad electrostatics I have used, these upgraded ESL-57s are easily the most revealing. One Thing say they are a big improvement upon those we reviewed in our October 2003 issue. Everything editor DP found was repeated with these upgrades. They were spectacular with large orchestral works, bringing an open, airy sound to Wagner for example; horns had strength, yet sounded wonderfully rich and natural. They called out magisterially from a vast sweep of an orchestra, strings behind sounding as smooth yet finely differentiated as you could ever wish for. A roll on a kettle drum had more power to it than I am used to, resonating nicely around my room. I fancy these ESL-57s have better dynamics, more volume and generally more vivacity and speed than I am accustomed to from any electrostatic I have heard before.


There is some slight sense of the metal front grilles being there still; I can perceive this because I have used 63s bare. All the same, when you hear natural instruments, like woodwinds, horns and violins through electrostatics as good as these you are reminded just how their lush timbral properties are twisted and sat upon by ordinary loudspeakers. Quads bring life to the gentle tranquility of orchestral ensembles, as they don’t lose resolution at low levels yet, in Lohengrin, when the orchestra rises to a brief crescendo it does so with a sudden force that is breathtaking through these 57s.


The same revelation the Quads bring to Rock vocals they also bring Classical vocals. There was a gentle purity to Renee Fleming’s voice singing 'Madame Butterfly'; it was a simple, uncluttered sound yet at the same time richly detailed and finely nuanced. And what they bring to Renee Fleming on CD, they improve upon with Eleanor McEvoy on SACD, as this source is the best we have at present, a quality these Quads are able to completely reveal.


Sadly, ESL-57s occupy space in my lounge I need for living in, and as amazing as they are, the need to keep them well ahead of rear walls means they take up more space than the outgoing Yorkminsters. But if you have a suitably proportioned room, then One Thing’s ESL-57s are a radical proposition, as their value could go up as you listen to what is one of the world’s most extraordinary loudspeakers. That would dry the tears from anyone’s eyes.



 verdict 4

One of the first electrostatic loudspeakers remains the greatest, courtesy of an amazing upgrade from One Thing Audio.




One Thing Audio
+44(0)2476 274573



- vivid clarity and detail

- unsurpassable revelation

- high resale value




- bright tonal balance

- little deep bass

- size


The One Thing Audio ESL57s have a rather saddle-shaped response, meaning that they peak in output towards both the top and bottom end of the frequency range. This means that they will have a tendency towards brightness but should also mean that they give very good upper mid and high frequency detail, along with good atmospherics.


Down the bottom end, the Quads roll off quite sharply below 60Hz, but peak up in output prior to this at around 80-90Hz. Consequently, they should have quite good low end punch and detail but will not dig all that low, compared to conventional box loudspeakers.


Electrically, the Quads measure like little else, with a single peak in impedance at 100Hz, rolling down both above and below this. Average measured impedance was 10.5 Ohms, but this dipped as low as 5 Ohms at LF and 3 Ohms at HF, so the One Thing Audio ESL57s do need some current from a suitable 4 Ohm amplifier tap. Sensitivity was average at 85dB. AS


FREQUENCY RESPONSE (what it means)



IMPEDANCE (what it means)



Comments (5)
Quad ELS 57
5Friday, 28 November 2014 17:40
Misha Norland
I have owned and loved these speakers since 1965. Recently serviced by One Thing Audio they have new life! There really is nothing to touch them, for installed in the right situation and driven by a good front end, the sound and staging is amazingly clear and shockingly life-like.
4Friday, 31 October 2014 14:29
carl hebb
Wish I had kept my late 57s. Years later I have not forgotten how wonderful they were, despite critical listening position. I have rebuilt 63s tucked away in a bedroom and stored that come out from time to time but they are just not the same. Carl.
One Thing Audio Quad 57's
3Monday, 02 June 2014 19:26
I don't think they are bright just new, a new pair of Quad 57 from Quad if you could still get them may sound bright due to being up to spec.
Quads not normally bright
2Monday, 09 December 2013 20:04
It sounds like they've modified the Quads and changed their warm character.

They haven't returned them to factory specs.

I agree with Manolis that original Quads aren't bright.

The One Thing Quad is a different animal.

Yes, the One Thing has a brighter balance, or you could say it is less warm. NK
ESL 57s rool!
1Monday, 07 November 2011 19:47
Manolis Kroussaniotakis
Thanks to your magazine, I got a used pair over 10 years ago, and listen only to LPs through a Rock II, EAR834P (again, your recommendation back then) and a Quad 405-II. Wow!

They will not be at the level of these reviewed here, but you know, wow! I had the panels replaced by Quad, Germany and also fitted a clamp.

It might be my ears/room but I do not hear them as bright, and I find tuneful bass that vibrates things my Castle Pembroke's could never. I listen to Heavy Rock and Blues mostly.

Now, I would like to hear them with a decent valve amp, but out here in Cyprus, options are kinda limited. And then there's that budget issue.

Like, wow! And you know, the space issue is very real, but consider this- all other speakers are "good enough" but none match these, life is too short, so get yourself a rectangular room, call it a "studio" (photos for me, art or music for you) and let the rest of the world and your nagging other half just, well, nag. They are that worth it :)

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