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.

The invention claimed is: 
     
       1. A ring-shaped surround for a loudspeaker comprising a driven cone set in a chassis, the surround bridging the gap between the cone and the chassis and comprising a membrane formed in a shape that, when relaxed, has a cross-sectional shape with a first portion connected to the cone and extending therefrom in a generally 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 and connected to the chassis wherein the second portion and third portion are in an approximately right-angle orientation, the first, second and third portions forming a Z-shape in which the second portion extends axially at an outer extremity of the first portion,
 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 so that the first and second joins form relatively sharp bends. 
 
     
     
       2. The surround according to  claim 1 , wherein the first portion has a surface which has undulations around the circumference of the surround. 
     
     
       3. The surround according to  claim 2  in which the undulations are in the form of bumps formed in the first portion. 
     
     
       4. The surround according to  claim 3  in which the bumps in the first portion are spaced equally around the circumference of the surround. 
     
     
       5. The surround according to  claim 1 , wherein the second portion which extends axially for the second distance has a smooth surface. 
     
     
       6. The surround according to  claim 1 , comprising an outwardly-extending flange for fixing to the chassis. 
     
     
       7. The surround according to  claim 6  in which the outwardly-extending flange extends from the second portion which extends axially for the second distance. 
     
     
       8. The surround according to  claim 1 , further comprising at least one tab extending from a surface of the second portion, in a direction transverse to the local orientation of the second portion. 
     
     
       9. The surround according to  claim 8  in which the at least one tab also attaches to a part of the first portion. 
     
     
       10. The surround according to  claim 8  in which the at least one tab also attaches to a part of the outwardly-extending flange. 
     
     
       11. The surround according to  claim 8 , wherein the first portion has a surface with undulations which extend circumferentially around the surround, wherein the surround comprises a plurality of tabs, and wherein a number of said tabs is equal to a number of said circumferential undulations. 
     
     
       12. The surround according to  claim 8  in which the at least one tab extends inwardly from the collar. 
     
     
       13. The surround according to  claim 1  in which the second portion extends from the first portion. 
     
     
       14. A driver for a loudspeaker, comprising a driven cone set in a chassis, and a surround bridging a gap between the cone and the chassis, the surround being according to  claim 1 . 
     
     
       15. The loudspeaker including a driver according to  claim 14 . 
     
     
       16. A ring-shaped surround for a loudspeaker comprising a driven cone set in a chassis, the surround bridging the gap between the cone and the chassis and comprising a membrane formed in a shape that, when relaxed, has a cross-sectional shape with a first portion connected to the cone and extending therefrom in a generally 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 and connected to the chassis, the first, second and third portions forming a Z-shape in which the second portion extends axially at an outer extremity of the first portion, and wherein the second portion which extends axially for the second distance has a smooth surface,
 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 so that the first and second joins form relatively sharp bends. 
 
     
     
       17. A ring-shaped surround for a loudspeaker comprising a driven cone set in a chassis, the surround bridging the gap between the cone and the chassis and comprising a membrane formed in a shape that, when relaxed, has a cross-sectional shape with a first portion connected to the cone and extending therefrom in a generally 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 and connected to the chassis, the first, second and third portions forming a Z-shape in which the second portion extends axially at an outer extremity of the first portion, and further comprising at least one tab extending from a surface of the second portion, in a direction transverse to the local orientation of the second portion,
 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 so that the first and second joins form relatively sharp bends.