LOUDSPEAKER WITH A NON-UNIFORM SUSPENSION AND AN ENFORCEMENT ELEMENT

Abstract

A loudspeaker with a non-uniform surround, a membrane and a stiffening element preventing the surround from flexing the membrane during operation. A non-uniform surround does not have the same cross section, along the radius of the speaker if circular, all around the perimeter of the membrane as some portions will be upwardly directed and other portions downwardly directed.

Claims

1.-15. (canceled)

16. A loudspeaker comprising a motor, a membrane, a surround and a frame, where: the motor is configured to move the membrane upwardly and downwardly along an axis, the membrane has an outer edge, the surround is connected to the frame and at least substantially all of the outer edge of the membrane, the surround has a first portion and a second portion, where: the first portion has a first radial cross section extending from a third portion of an outer edge of the membrane to a point of the frame being the closest to the third portion, which first portion is directed upwardly, and the second portion has a second radial cross section extending from a fourth portion of an outer edge of the membrane to a point of the frame being the closest to the fourth portion, which second portion is directed downwardly, the loudspeaker further comprising a stiffening element provided at the outer edge of the membrane, wherein a portion of the surround, between the first and second portions, has a cross section with an M or W shape.

17. The loudspeaker according to claim 16, wherein the first and/or second radial cross section has a U or V shape.

18. The loudspeaker according to claim 16, wherein the surround defines, along a central, closed curve thereof, a repeating pattern.

19. The loudspeaker according to claim 16, wherein the stiffening element has a portion with a radial cross section which has a shape of a closed curve.

20. The loudspeaker according to claim 19, wherein the stiffening element is hollow.

21. The loudspeaker according to claim 19, wherein the stiffening element is filled by a filling material.

22. The loudspeaker according to claim 19, wherein the stiffening element has a portion with a radial cross section which has a shape of a polygon.

23. The loudspeaker according to claim 22, wherein one side of the polygon is formed by the membrane.

24. The loudspeaker according to claim 19, wherein the stiffening element has a portion with a radial cross section which is oval.

25. The loudspeaker according to claim 16, wherein the stiffening element forms a closed curve in a predetermined plane.

26. The loudspeaker according to claim 25, wherein the combined membrane and stiffening element has, when projected on to the plane, a mass per area which is higher at the stiffening element than inside the closed curve.

27. The loudspeaker according to claim 16, wherein the diaphragm and stiffening element have a first mass per area, in a plane perpendicular to a direction of movement of the membrane, and the diaphragm has a second mass per area in the plane at a position not at the stiffening element, where the first mass per area is higher than the second mass per area.

28. The loudspeaker according to claim 25, wherein the combined membrane and stiffening element has, in a direction perpendicular to the plane, thickness which is higher at the stiffness element than inside the closed curve.

29. The loudspeaker according to claim 16, wherein the stiffening element is configured to prevent flexure of the outer edge of the membrane during movement of the membrane.

30. The loudspeaker according to claim 27, wherein the combined membrane and stiffening element has, in a direction perpendicular to the plane, thickness which is higher at the stiffness element than inside the closed curve.

31. A method of assembling a loudspeaker, the method comprising: providing a membrane having an outer edge, providing a surround having a first portion and a second portion, where: the first portion has a first radial cross section extending from a third portion of an outer edge of the membrane to a point of the frame being the closest to the third portion, which first portion is directed upwardly, and the second portion has a second radial cross section extending from a fourth portion of an outer edge of the membrane to a point of the frame being the closest to the fourth portion, which second portion is directed downwardly, wherein a portion of the surround, between the first and second portions, has a cross section with an M or W shape, providing a stiffening element and fixing the outer edge of the membrane to the surround and the stiffening element.

Description

[0065] In the following, preferred embodiments of the invention will be described with reference to the drawing, in which:

[0066] FIG. 1 illustrates a radial cross section of a loudspeaker according to the invention,

[0067] FIG. 2 illustrates a first embodiment of a stiffening element and the projected thickness thereof,

[0068] FIG. 3 illustrates a second embodiment of a stiffening element,

[0069] FIG. 4 illustrates a third embodiment of a stiffening element,

[0070] FIG. 5 illustrates a first embodiment of a non-uniform surround,

[0071] FIG. 6 illustrates a second embodiment of a non-uniform surround,

[0072] FIG. 7 illustrates alternative membranes with thicker or different materials at the outer edge and

[0073] FIGS. 8-13 illustrate different types of stiffness elements.

[0074] In FIG. 1, a loudspeaker 1 is illustrated having a membrane 2, a motor 4, a frame 6 and a surround 8. The motor is configured to move the membrane upwardly and downwardly along an axis A, and the surround is configured to prevent air from passing around the outer edge 12 of the membrane 2 and to control the movement of the membrane 2. The surround 8 is connected at its outer periphery to the frame 6.

[0075] When the surround is not completely uniform, the movement of the membrane will cause the surround to flex which again will cause the membrane to flex during the movement. This flexing causes distortion of the sound output, which naturally is not desired. In FIG. 1 the surround 8 is shown as non-uniform as evidenced from the different shapes of the left-hand and right-hand cross sections.

[0076] Non-uniform surrounds may be seen in FIGS. 5 and 6. The surround in FIG. 5 may be seen in U.S. Pat. No. 6,516,077 and has a number of ridges 18 directed tangentially to the outer edge 12. The remainder of the surround has the shape illustrated at 16. Clearly, different portions of this surround have different radial cross sections and thus different effects on the outer edge 12.

[0077] The surround in FIG. 6 may be seen in EP0556786 where a portion of the surround, in the cross section seen in FIG. 1, is directed downwardly and a portion is directed upwardly, where the intersection between these portions looks like that in FIG. 6. Clearly, the portion illustrated in FIG. 6 will have a different effect on the membrane than a half-roll portion as seen to the extreme left and right of the same figure.

[0078] These different effects on different portions of the outer edge will bring about a flexure of the membrane when moved.

[0079] In order to counter-act this flexing, a stiffening element 10 is provided at the interface between the membrane and the surround. FIGS. 2-4 illustrate different shapes of such stiffening elements.

[0080] The flexure of the membrane is a deformation that causes portions of the outer edge to be pulled towards the central axis of the membrane and other portions to be pushed away from the central axis. Different modes of flexure will exist, where a first mode is one in which the outer edge becomes oval. A second mode is one wherein the outer edge has three lobes, and in a third mode, it has four lobes. Clearly, any number of lobes may be seen when flexing the membrane.

[0081] FIG. 2 shows a radial cross section, of the outer edge 12 of the membrane 2 and a stiffening element 10, where the radial cross section of the stiffening element is rectangular. One of the sides of the rectangle may be made up of the membrane material. The stiffening element extends along the outer edge of the membrane, typically as a closed curve when projected to a plane perpendicular to the axis A. Clearly, the stiffening element will counter-act the flexure of the outer edge 12. Also shown is the projected thickness of the assembly of the membrane and the stiffening element onto a plane perpendicular to the central axis A.

[0082] The radial cross section of the stiffening element may have any desired shape. In FIG. 3, the shape is triangular. Again, the membrane material may form one of the sides. Advantageously the shape may be a closed curve like a rectangle, polygon or oval.

[0083] In FIG. 4, the radial cross section of the stiffening element has a circular shape.

[0084] Naturally, any shape of the stiffening element may be used. A polygon may be used, and if desired, one or more sides may be formed by the membrane.

[0085] The stiffening element may be hollow or may be filled by a filling material, such as a foam.

[0086] The stiffening element may be made of any type of material. The stiffness, clearly, is desired high, but the weight is desired as low as possible. Thin aluminium, such as with a thickness of 0.5 mm or less, such as 0.25 mm or less, such as 0.2 mm or less, such as 0.15 mm or less may be used, as may other materials, such as metals, alloys, polymers, paper, cardboard, plastics, composite materials, Kevlar or the like.

[0087] A separate stiffening element may be replaced by an adaptation of the membrane material. Usually, the membrane is made of the same material with the same thickness, perpendicular to the extent of the membrane, over the full surface of the membrane. However, the membrane may be made thicker at the outer edge so as to increase the stiffness thereof.

[0088] Further alternatively, the membrane may be made of another material or an additional material at the outer edge in order to increase the stiffness at the outer edge. This is illustrated in FIG. 7. A thicker layer of a material tends to be stiffer than a thinner layer. Also, the outermost portion of the membrane may be made of a stiffer material than the remainder of the membrane so as to increase the stiffness of the membrane at the outer edge.

[0089] FIGS. 8-13 illustrate further types of stiffening elements where FIG. 8 illustrates the addition of a thin layer of e.g. paper extending in the direction of the movement, whereas in FIG. 9, a layer of e.g. paper is provided extending in the direction perpendicular to the direction of movement. Alternatively, the square of FIG. 10 may be used, as may the circle of FIG. 11, the 45 degrees square (diamond) of FIG. 12, or the triangle of FIG. 13 having a 90-degree angle and a largest side extending in the direction of movement of the membrane.

[0090] Clearly, a number of different stiffening element types, shapes and the like may be used. Other materials may also be used in order to tailor the properties even more.