For at least as long as I’ve been aware of the original Quad electrostatic loudspeaker— close to 50 years now— there have been folks who have tried to improve those speakers.
The targets for improvement have been:
-Greater bass extension and impact;
-Broader dispersion, allowing more than one listener in the “sweet spot”;
-Greater treble extension.
The most famous of all “Quad mods” sought to improve all three aspects: Mark Levinson’s HQD System. For those not around back in the day, the Initials HQD stood for Hartley Quad Decca. Levinson—still the man, not a corporate entity—designed a frame that would hold stacked Quads for greater SPL and a larger sound-source, then inserted the Stanley Kelly-designed Decca ribbon tweeter between the two Quads on each side, crossing over at 7 kHz, the frequency above which the Quad treble panels really stated to beam. Separate woofer enclosures utilized the milky-white 24″ Hartley woofers, perhaps not the ultimate in controlled bass or the best match for the Quads, but they were big and impressive and scarce. Levinson matched all the speakers with his electronics (surprise!): the ML-2 Class-A monoblock amps, designed by John Curl, 25 watts that would drive almost anything. There were also custom electronic crossovers and a Levinson pre. The whole shebang ran about $26,000 in 1984, and left Stereophile‘s J. Gordon Holt thoroughly unimpressed.
[Sidebar rant: the $26,000 cost of the HQD system in 1984 was viewed by JGH as horrifically-expensive and of interest to only a few of his readers. In 2017 bucks—that’s this week, who knows about next week—that price translates to about $60,000 today. And given today’s prices, it’s hard to conceive of that much hardware only costing $60,000. Hell, for many high-end speaker brands these days, $60k is entry-level. What happened?? end of rant. ]
in 1994, Chris Beeching wrote in Hi-Fi News about a number of Quad mods and variants: stackers (like Levinson) included SME owner Alistair Robertson-Aikman; Russ Andrews in the UK offered a beefed-up power supply; and in the US, John Koval’s Quad Mod was a new crossover unit that some loved, some hated.
(After the ESL-63 appeared, a new generation of mods appeared. Most famous in the US was the Crosby mod, which stiffened the ’63’s somewhat flexible frame, among other changes. Oddly, almost no info on the Crosby mod can be found on the web. But the ’63 is outside the scope of this article.)
Our old friend and Copper contributor Haden Boardman is one of the world’s foremost authorities on vintage hi-fi gear. Here’s what he has to say about the Quad ELS-57, and Tim de Paravicini’s direct-drive Quad mod:
“My early interest in hifi was initially read, rather than fully experienced, and my first ever introduction to the written world of Hifi was an English 1969 Hi-Fi Year Book (incidentally a very good year!) inherited from my Grandad Fred when I was aged 10. I read that book cover to cover like 10,000 times. I studied every piece of hifi in it, and on the cover was QUAD.
“It was pretty clear from just the cover that QUAD was cool. As a company they have never feared using a good out-of-house design consultant for aesthetic design, advertising and literature (present corporate fathers IAG, take note).
“Which brings us to the original electrostatic. A speaker practical and petite as an electrostatic speaker can be… Electronics-wise two bass panels flank a central mid/treble unit. The audio transformer steps up the amplifiers output, and via its carefully worked out secondary loading and ingeniously simple crossover loads the panels with high enough voltages for the physical modulation of the air by the panel. The bias voltage is supplied by an early solid state extra high tension (EHT) unit, really remarkable for the time. A wooden frame holds the ensemble, with a metal grille front and rear, and dainty little feet.
“It was 9 or 10 years from the time when I read about the QUAD electrostatic to the time when I actually heard one—and that was actually the later ESL63. Nonetheless, it completely exceeded my expectations. Still a teen, I just had to have a set, and managed to find a pretty messed-about-with pair of original ‘57s for the kind of money I could afford (£150 in about 1988).
“Neither side of the pair sounded that good, and disappointed was I.
“A conversation with a QUAD service engineer at the time was just amazing. He took the time to fully explain aging in the panels and the drop in efficiency of the original EHT units, plus how the panels were made, what mods had been done to them, etc. It cost me another few quid for new EHT units, but then I had a working pair of electrostatic speakers.
“Mods are rather obvious and have been well covered: ditching the cutesy feet for a proper stand; removing the “wadding” from behind the midrange / treble panel. If your listening room is isolated, and you aren’t plagued with rug rats or pets, removing the metal grilles makes a goodly difference also. If you have house room and a suitable wallet, stacking them makes a lot of sense. I heard a triple stack once, and that was pretty awesome.
“The best sounding set ever was when Tim de Paravicini was “told” by a certain smart ass magazine editor that it would be impossible to direct drive the Quad panels direct off a tube amp. Now, Tim, being Tim, [HA! —Ed.] already had the idea planned out in his head long before the challenge was thrown down, and those lucky enough to visit the 1993 Hi-Fi News show were given the treat of hearing an uninhibited electrostatic speaker. Devoid of its audio transformer and driven directly from the anodes of a couple of PL519 tubes, glowing brightly with 19,000 volts on each anode, 38,000 volts across the two. The power supply for the amplifier was lethal, sadly making the chances of productions zero, even if the sound was to die for [perhaps literally–Ed.].
“Tim’s rather unique driving style is famous. The two chassis were built in big “U” shaped enclosures, and [while transporting the amps] Tim’s driving had thrown one of the large chassis against the back seats of his car, bending one side of the “U” slightly inwards towards the 38kV inside. (I’m exaggerating- it was just one side, a mere 19kV) This was not noticed until… on initial powering up, the said few kV now had an easier path to ground, jumping through the reduced gap from a ladder of 3 watt resistors acting as anode load (must of been twenty per tube) and directly arcing to the chassis. One little 3 watt resistor took the brunt. The resulting arc and current flow totally dissolved the resistor in the air, and resulted in a permanent X-ray of yours truly in one of the bedroom walls of the then Ramada Hotel, Heathrow!
“Oh to be young and foolish….
“I still have electrostatic speakers in the ‘family’ but my discovery of high SPL horn speakers pushed the units out of my main listening spot. In standard trim, I find the speaker frustrating: it’s so damn good. The bass plays deeper than anyone generally gives it credit, but freed up from the usual cone resonances and tuned bass ports, the lack of bass “color” can be underwhelming for some. But the reason they aren’t my ‘daily drivers’ is simply the lack of SPL. They do some things and some genres better than any other speaker I know, and if you are in a smaller room or really don’t listen at excessive levels, you are probably listing to the best speaker in the world.
“Unlike conventional speakers, the panels fade and need to be rebuilt with age. This can make a £150 set cost more like £800. When tracking a set down, budget on panel replacement before you give yourself a shock!” [pun not intended, I trust–Ed.]
Today, 60 years after their introduction, the original Quad electrostatic loudspeakers still provide business for a cottage industry of rebuilders and improvers. Instructions can be found on the web for a number of standard tweaks like removing the dust-covers and the damping material; either one may shorten the lifespan of the speakers and make them more open to prying fingers. Such modded Quads are not suitable to homes with cats, small children, or a lot of dust.
Those in the field of Quad ESL restoration and/or improvement include True Sound, ElectroStatic Solutions, and Quads Unlimited in the US; Sheldon Stokes, and Classique Sounds/One Thing Audio in the UK. There are undoubtedly others in those countries, and I’ve seen listings from specialists in Canada, Australia, and Germany.
Unlike many pieces of vintage gear, the ’57 still has a strong support community. Original units will undoubtedly need attention, but there are plenty of choices in parts and repair options.