Quad ESL 2812X Electrostatic Speakers

One would be rightly forgiven for knowing of the ESL but not knowing how the ESL differs from typical loudspeakers. It us correct to begin with the fact that a QUAD ESL is not your typical loudspeaker! Unlike conventional speakers that use moving-coil drivers, the ESL employs a completely different principle: an electrostatic panel.

At the heart of a QUAD ESL are panels containing a diaphragm of fine Mylar film, ten times thinner than a human hair. The Mylar film is coated with a high resistance conductive material and suspended between two perforated metal plates called stators.

This unique diaphragm is incredibly light and therefore dynamically responsive. It is much lighter than any moving-coil driver cone and can therefore respond to signal transients with incredible speed and accuracy.

The Mylar diaphragm is charged up to a constant high voltage exceeding 5.2kV DC. An audio signal is applied across to the two stators to create an alternating electric field, which causes the charged electrostatic Mylar diaphragm to be alternativley pushed and pulled towards them. As a result, the diaphragm vibrates accurately in response to the music signal, and so produces the ultra-pure sound reproduction for which QUAD ESL loudspeakers are well-known.

Due to the diaphragm's lightweight nature and uniform drive across its entire surface, the sound it generates is exceptionally clean, responding accurately to musical transients, and exceptionally low in distortion, particularly intermodulation distortion. This is particularly evident in the midrange frequencies, where human hearing is most attuned.

“Point Source” Design

Peter Comeau, QUAD’s Director of Acoustic Design, has monitored the development of the ESL X closely and comments as follows:

“The X suffix for the new QUAD ESL 2912 and 2812 speakers suggests something eXtra and that is certainly delivered in the sonic performance of these models.

First of all the inclusion of UK built audio transformers, built precisely to Peter Walker’s original specification, provides wider bandwidth, especially at the high frequency end where the extra extension offers superior clarity to instrumental harmonics as well as lending more air to the spatial acoustics.

Secondly, an all new PCB board layout splits the audio components from the high tension section and optimises the latter to provide a more stable 5kV supply to the electrostatic panels. This benefits both the precision of instrumental timbres and, not surprisingly, the transient attack, particularly in the bass region. Finally a new grille cloth, specially chosen to match the matt black finish of the speakers, offers improved acoustic transparency which helps realize the full benefits of the new internal components.

The result is yet another incremental advance of the musical performance of the QUAD ESL, still considered the most uncolored, natural and transparent-to-the-source hi-fi loudspeaker.”