A short history of the Quad Electrostatic Loudspeaker is impossible to write, as are many other histories, without some background. So, I am writing here in an historical context for the Quad ESL, not a vacuum. For those readers who prefer a purist, technical history, there is the Hard Core Patents section of this site, which I am sure will keep the technophiles amongst you enthralled for hours. The history of electrostatic devices is actually broader than one might at first suppose, and certainly not confined to electrostatic loudspeakers, as the following pages will show: