QUAD ESL 2905, ESL 2805 manual ElectrostaticThe, Alternative

ElectrostaticThe

alternative

Although deeply flawed, their cost and convenienceadvantagesaresuchthatthe overwhelming majority of loudspeakers in today’s marketplace are moving-coil, and at Quad we manufacture some of the finest examples of this genre. But, as a counsel of perfection, we have to look elsewhere.

Electrostatic speakers have long been renowned for their superlative accuracy and clarity in mid-range and upper frequencies but deficiencies in the bass response and indifferent dispersion characteristics have presented difficulties which few manufacturers have satisfactorily overcome. Many hybrids have been attempted over the years which combine moving-coil speakers in the bass with electrostatics handling the upper registers, but these designs have not been successful.

An electrostatic speaker is a plastic membrane which is coated with a resistive material and suspended between two perforated metal plates. A polarising voltage of several thousand

volts is connected to the membrane which at rest is suspended at an equal distance between the two plates. When an audio signal (also stepped up to a few thousand volts by a matching transformer) is applied to the metal plates, the varying signal across the plates attracts or repels the membrane, and sound is reproduced. Because the membrane is extremely light, and driven across its entire surface, transient response and freedom from overhang is exemplary – quite unlike moving-coil loudspeakers.

Of course, if it were as simple as this, there would be many more electrostatic loudspeakers. The challenge has been to produce an electrostatic loudspeaker with extended bass response and a satisfactory dispersion. Virtually none have succeeded. A combination of acoustic problems and extreme difficulties of manufacture has resulted in a bare handful of true full-range electrostatic loudspeakers being available to the audiophile and in this field Quad are pre-eminent.

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