If that failed, the input was shorted by an electrical "crowbar," activated by an RF "sniffer" that detected the ionization of air that occurs just before an electrostatic speaker arcs. The circuit operated by limiting voltage at the input. The ESL-63's second major innovation was its triac clamping circuit, to protect the speaker from arcing. A microphone placed between the speakers showed that the two signals canceled each other out completely. This design had near-perfect phase coherence, as shown by Quad's show-stopping demos, in which two squarewaves out of phase with each other were fed to two Quad speakers. The ESL-63's single electrostatic element also eliminated the Venetian-blind, treble-beaming effect found in speakers with multiple panels.
#HIFISHARK ESL 57 DRIVER#
The first was the speaker's unique radiating element, which used driver plates that employed a printed circuit board of concentric rings fed by delay lines comprising some 12 miles (!) of wire, which allowed the flat diaphragm to radiate the sound first at the center and last at the periphery, as if it were a radiating sphere-the ideal shape for approximating sound emanating from a point source 12" behind the panels. Quad designer Peter Walker sought electrical and sonic relief in the next generation, the ESL-63, which premiered at the 1981 CES (footnote 1) and featured two major innovations.
#HIFISHARK ESL 57 HOW TO#
Wilson's Peter McGrath, then running Sound Components in Miami, offered to teach me how to do my own Quad repairs using rolls of Mylar and a hairdryer. Worst of all was the danger of arcing-the flickering blue lights in the panel that signaled diaphragm perforation and destruction. Left on, it sucked up dust and grime as its panels filtered the air. Configured as a gnarly, stubby panel, the speaker was often mistaken for an oversized space heater. This required an amplifier designed to swing low amounts of voltage while remaining stable the Quad 303 and the Levinson ML-2 worked the best. The driving amplifier had to be able to handle the '57's capacitive load, whose impedance fell to 1 ohm at high frequencies. The speaker had low power handling, high-frequency beaming, limited bass response, and widely fluctuating impedances. However, owning a pair of ESL-57s required dedication and a generous masochistic streak. The speakers' curved rectangular panels imaged beautifully, yielding an extraordinarily lucid midrange, speed, and transparency. It employed a "constant charge" feature to distribute electrons across its entire Mylar diaphragm. The first Quad loudspeaker was the ESL-57 (the number indicates the year of design), which remained in production for 25 years. Today, full-range electrostatic speakers are even rarer.
#HIFISHARK ESL 57 FULL#
Back in 1989, when I last did a full review of a Quad ESL for Stereophile, it was one of only 11 full-range electrostatic systems listed among 1376 loudspeakers in Audio magazine's "Annual Equipment Directory." These 11 models were made by only four of the 257 speaker companies listed. The ESL-989 is the fourth version of the longest-surviving consumer-grade electrostatic speaker, which is now approaching its 45th year of sales. Just as Prague's historical richness enhanced the classical-music performances I heard, the Quad ESL's unique reputation was appealing on its own. I was already strongly attracted to the speaker for its unique place in the history of high-end audio.
Similarly, Quad's ESL-989 electrostatic loudspeaker caught my visual attention before I ever heard them. But this memory mixed the music with the beauty of Prague's soaring church spires, brilliant red terracotta roofs, and lavish palaces. In response, a massive wall of deep organ chords shook the hall, the magical acoustic blending the delicate, extended highs with the thunderous bass. I recall seeing the delicate, youthful Michele Hradecka sway from side to side to reach the pedals. I first heard Eugene Gigout's pipe-organ masterpiece, the Grand Chorus in Dialogue, in the Smetana Concert Hall of Prague's Municipal House (Obecnim Dome) on a Saturday evening before the 2002 flood.
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