The recent appearance of a full range ESL designed and produced by a well-known manufacturer specialising in high quality reproduction, was bound to cause considerable comment and speculation. This speaker, the "Quad" electrostatic, is now in production, and we are pleased to present our readers with a full review of a specimen drawn from current production. The makers are The Acoustical Manufacturing Co. of Huntingdon, and it can be obtained through the usual channels. Price £52.

The Quad is a full-range electrostatic speaker, covering from slightly below 50 cps to well above the limits of audibility. Having no heavy cone or voice coil, it possesses very low mass and correspondingly fine transient response.

If Harold Black did not actually invent negative feedback, he was certainly the first to show a comprehensive knowledge of the subject in his famous patent of 1937. Nine years earlier, he took out a patent on feed-forward error correction.

...It was designed as a mono device. After we made 500 or 600, stereo came in, and it was modified to give better directivity because of the interferences in stereo..

"This all-time classic needs no introduction to any audiophile who knows enough to read equipment reviews at all. It has survived virtually unchanged for a quarter of a century (the manufacturer claims there have been no changes whatsoever, large or small, but we take that with a grain of salt); we, too, keep invoking its name all the time, and yet we never reviewed it

The history of this amp's circuit starts twenty five years ago when Julius Futterman, understanding the limitations of the output transformers. patented an Output Transformerless design. The clarity of the sound has been unsurpassed to this day and a cadre of serious music listeners has remained steadfast to the genius of Julius Futterman.

A good electrostatic has something special, a magic spell that weaves itself over you. Critics (of which there are few) moan on ~bout "won't play rock" or "only for string quartets". Ask these plaintiffs what system they have, or what kind of speakers, and the usual response is some old west coast monster.

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