Refurbishing Classic Quad Electrostatic Loudspeakers

The original Quad design — later dubbed the ESL57 when a newer version came out named the ESL63 — is comprised of a treble panel flanked by two bass panels, with the membranes being constructed from 6 and 12 micron tensilised film respectively. Even with an excellent design such as the ESL57 it is still possible to burn holes in the bass panel membrane due to arcing from over-driving the loudspeakers. As noted at the start of this post you should not attempt this sort of repair unless you are qualified at working with high voltages; mains, 6kV output from the PSUs and the high voltage audio output from the step-up transformer all present significant risk!

Source: www.rs-online.com