The
LEAK Sandwich was an innovative
loudspeaker design introduced by the English hi-fi company
H. J. Leak & Co. in 1961. Harold Leak engaged Don Barlow, who had devised a way of making the cone of the loudspeaker from expanded
polystyrene foam sandwiched between two sheets of
aluminium foil. This made it both very light and extremely stiff, and correspondingly accurate in sound.