AOM Logo April 1998


Quad ESLs: Then and Now

Blair Roger

Can a loudspeaker be all things to all people? Probably not, but the Quads take a damn good shot at it and I'll dispute anyone who says otherwise.

Genesis
Peter Walker and his engineering team have been unconventional and pragmatic thinkers since S. P. Fidelity Sound Systems was founded in 1936. By 1938 they were manufacturing a portable public address system under the name of The Acoustical Manufacturing Company. A year later came a direct-coupled class A amplifier with separate pre-amp and tuner in a bookshelf-size case for domestic use. In 1940 the battery powered public address amp known as the C25 Acoustical Amplifier was introduced. Boasting greater than 20 Watts output with low distortion, promotional literature for this valise size unit trumpeted: "ADDRESS 150,000 PEOPLE FROM YOUR CAR BATTERY". The war years must have been good to Acoustical. In 1949 the company produced a huge corner horn-loaded speaker with a ribbon tweeter capable of reproducing higher frequencies than any other loudspeaker of its day.

Igor, It's Alive!
Shortly after that, we have some evidence in the form of experimental drivers that indicate Walker was tussling with the problem of electrostatic sound reproduction. How he latched onto this idea and clung to it so tenaciously is a mystery to me. The principal of an electrostatic driver was known in the 1920s but the limitations imposed by physics made it impractical to build. I suspect that Walker heard a hint of the potential promised by the design around 1950, and set his sights on developing the speaker with single-minded determination.


Imagine for a moment, lazing in a hammock and being caressed by gentle summer zephyrs. This is the original Quad at its best.

It is rumored that when introduced at the London Audio Show in the mid-1950s, the speaker we now call the ESL-57 caused many conventional speaker manufacturers to wonder how long they, themselves, would survive. "Walker's Little Wonder" was a remarkable achievement, even measured by today's standards.

Put in perspective, we must remember that the unit was originally meant to be used as a monophonic reproducer in the close quarters typified by the average British home of the time. It was designed for music lovers at a time when other system components lagged far behind, and the notion of 'high end' was inconceivable. Cartridges, tonearms, turntables, and recordings were just emerging from what we now call the 'historic' period dominated by 78 r.p.m. shellacs. Was Walker anticipating the development of stereo with its demands for phase accuracy and wide frequency response? In my mind, this is a certainty.

The phase coherency and the consistent frequency response of the ESL-57 are its basic strengths. These qualities made it an outstanding reproducer even in the early days. Coupled with shocking transparency, they allow one to overlook the shortcomings of the speaker even today.

Reference Components

Upstairs, where we spend most of our time, I have a beautiful mint pair of late production ESL-57s driven by an unrestored and unrepentant Fisher 500B tubed receiver. After acquiring these speakers, I couldn't rest until I'd found a pair of USA Monitors for my main system downstairs. Currently, the Monitors are partnered with a YBA 3 alpha amplifier, an Audio Research SP-9 Mk II preamplifier, and a Well-Tempered Turntable with Lyra Lydian cartridge. Of course, the ESL57s saw time in the main system downstairs for the purpose of this review.

-- Blair Roger

The Sound (of One Speaker Clapping)
Taken on its own terms, the ESL-57 is a thoroughly satisfying speaker. Imagine for a moment, lazing in a hammock and being caressed by gentle summer zephyrs. This is the original Quad at its best. If I could have only one pair of speakers for the rest of my life I would be content with these. They let me listen to the music and feel the lyrics instead of wondering if I need better cables.

The musical limitations of the design are primarily a result of physics and technology. The reproduction of bass frequencies is the biggest challenge the designer faces. Obtaining response extending into the octaves below 100 Hz requires increasingly larger panels. As the panel grows, it becomes more demanding on the electronics, to the point of economic and physical impossibility. Walker took a different tack, and cleverly blended three panels into one unit capable of delivering wide frequency response with near-seamless coherence. The result was a musically satisfying design with surprisingly good imaging and quite acceptable dynamic capabilities. In addition, huge amounts of power were not required to achieve good listening levels. This was certainly a bonus for owners of the 15 Watt Quad II (Quality Unit Amplifier Domestic) amps sold at the time.

In comparison to the ESL-63, the bass is dryer and not quite as fulfilling. Dynamics are less pronounced and some drummy resonances from the metal screens are excited in the loudest passages. A slight congestion in the midrange imparts a legato effect on some recordings. This was evident while auditioning Bach · Kreisler · Ysaye, a solo violin recording on Water Lily Acoustics [WLA-WS-07] by Arturo Delmoni. A sensible limit on listening levels is necessary unless one is willing to risk arcing, which will damage the Mylar panels now said to be unavailable from Quad. Any good quality amp between 8 and 30 Watts with a stiff power supply is suitable for driving these speakers without harm, provided one exercises reasonable caution.

Quad ESL-57The highest treble is very directional and this means that the speakers must be angled inward, towards the listener or they will sound excessively dull and closed-in. This is probably the most contentious issue surrounding the ESL-57: the "beamy" treble and the restricted listening position it causes. Sadly, no solution exists for this, so resign yourself to hours of solitary listening or constant scrimmages for the sweet spot.

On the plus side, their transparency is astonishing and something once heard, never forgotten. The sound just seems to come from somewhere in and around the speakers and one can - given the right associated equipment - see into the soundstage with exceptional clarity.

Where it exists on the recording, ambiance reproduction is excellent, and the atmospheric Delmoni recording mentioned above is an outstanding example of this. What this indicates is a superb ability to resolve the subtle details of decaying sounds, and is a natural outcome of the speaker design.

Some will say that the imaging is slightly diffuse, but I hold this to be consistent with what we experience at a live concert, where the sounds are blended by the hall acoustics. This too, contributes to the realism of the picture the ESL-57s paint. The RCA Classics pressing of Claire de Lune [LSC-2326] conducted by Agoult is a mellow, seductive tour de force for these speakers. Speaking of seduction: I've got to say that the reproduction of the human voice is the true forte of the Quads, old, and new. If you've got it, give a listen to the classic They Can't Take That Away From Me on Windham Hill Jazz [WH-0116] as sung by Patti Cathcart in a smoky, jazz mezzo voice while Tuck Andress strums through the changes on his Gibson in a spacious acoustic. What the Quads do with this cut will leave you breathless.

Enter: FRED, Lord of the Rings
The ESL-57 is a classic loudspeaker in its own right and a thoroughly satisfying one to listen to. Nevertheless, Quad decided to address some of its more serious deficiencies with the FRED (Full Range Electrostatic Doublet) project that officially commenced in 1963. The need for a speaker that was more robust, capable of greater dynamics with extended frequency response and improved treble dispersion was a pressing issue. The complexity of the undertaking is hinted at by the fact that the loudspeaker did not actually appear until 1981. Peter Walker must have felt himself faced with a great challenge: daring to improve upon the ESL-57's success. It would require a radical revision of thinking, design, and engineering.

The first major difference between the old and new Quad speakers is the dipolar radiation pattern chosen for FRED. The ESL-57 was designed to radiate only from the front, and this makes it quite easy to set up in confined quarters. A true dipole has sonic advantages and will sound more spacious and airy, particularly in the lowest octave, but it needs more room to breathe. Many people think that ESL-63s are bass shy. The speakers are in fact, capable of prodigious bass. They must be positioned five feet or more from the back wall so that the rear wave does not have a canceling effect on the front wave at low frequencies.

Quad ESL-63 loudspeakerThe second innovation incorporated into the ESL-63 is the concept of the delay-line signal path. Imagine concentric rings of conducting wire (electrodes) covering the surface of the speaker panel. The feather-light membrane at the heart of the speaker is induced to vibrate by the alternating music signal traveling through the electrodes on the front and rear panel. As the music signal is fed first to the centre section of electrodes and then to each ring in turn, the music emanates from the centre to the edge of the panel like ripples from a pebble dropped into a pool of water. The effect mimics a point source of sound focused about twelve inches behind the plane of the speaker. The result for the listener is a speaker that is remarkably open, quick, and natural.

Many other weaknesses were addressed as well. Any amplifier between 50 and 200 Watts that is stable into 8 Ohm capacitive loads can be used with confidence. The ESL-63 has a vastly increased tolerance for volume demands and protection circuits that will shut down the unit to prevent damage to the panels. Great attention has also been paid to making the signal phase response more accurate and coherent. This has resulted in improved decay characteristics that make the speaker sound quicker, clearer, and more realistic, especially in the reproduction of percussive transients. This has also meant better midrange detail and an overall improvement in transparency.

A perfect example of this is the recording of Toru Takemitsu's Waterways by the ensemble, Tashi [RCA ARL1-3483]. The group consists of clarinet, piano, violin, cello, harps, brass, and a variety of percussion instruments. The piece was recorded in a large studio with simple microphone techniques. The music is spare and evocative, depending more on timbre and dynamics than rhythm to express the composer's ideas. The ESL-63s present a spacious vista sparsely populated with islands of sound ranging from a piano echoing in the darkness, to the thunder of a bass drum and raucous blasts from the brasses.

The new speaker has the ability to handle a wide spectrum of music from solo wind instruments to strings, brass, percussion, and symphony orchestra with conviction and aplomb. The excellent Solti recording, Venice [RCA-2313] is a great example of how adept the ESL-63s are at handling the breadth, depth and dynamics of an orchestra going full tilt. Listen to the overture to Rossini's Semiramide. The Orchestra of the Royal Opera House stretches beyond the bounds of the speakers. Depth is exceptional. What a roller coaster of dynamics. Hang on…and enjoy the ride!

End Game
What does this all add up to? Simply an outstanding line of loudspeakers, the elder bested only in head-to-head comparison with the younger. These are arguably the best electrostats made in this century, and certainly the best loudspeaker of any design type available at realistic cost the high end has seen so far. They have an absence of box resonances because (surprise!) there is no box, and an openness and truth to timbre over their entire frequency range that is matchless. They are capable of superb stereo reproduction and have a breathtaking way with vocals even on less-than-holy recordings. This goes for all versions of the Quad I have heard: the '57, the '63, and the USA Monitor.

What really distinguishes them is their overall balance in every area: the ability to play as loudly as one can reasonably expect; a realistic tonal balance in which no area is unduly emphasized; a sensational sweetness in the mid-band and finally, standard-setting transparency in the treble.


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