Surrounds for audio drivers

Abstract

A ring-shaped surround for a loudspeaker is disclosed, in the form of a membrane formed in a shape that, when relaxed (i.e. when not being driven), has a cross sectional shape with a first portion extending in a radial direction for a first distance, a second portion extending in an axial direction for a second distance, and a third portion extending in a radial direction for a third distance, the first and second portions being connected by a first flexible join, and the second and third portions being connected by a second flexible join, the first join having a first radius of curvature that is shorter than at least one of said first and second distances, the second join having a second radius of curvature that is shorter than at least one of said second and third distances. Thus, the surround has a Z-shape, with a first radially extending portion, and a relatively sharp bend leading to an axially-extending portion. The radially outwardly extending portion can have a surface which undulates around its circumference, to provide a stiffening effect to the otherwise planar surface and inhibit resonances. One or more tabs can be provided, extending from a surface of the second portion, in a direction transverse to the local orientation of the second portion. These will adjust the dynamic properties of the surround as required. Typically, the surround will be circular, to fit around a circular driver. However, other shapes are possible.