Radiating domes for loudspeakers

Abstract

 A radiating metal dome for use in loudspeakers is made of copper, silver or gold, or of an alloy of one of these metals with additions not sufficient substantially to reduce the thermal conductivity. This ensures good heat dissipation from the coil (14). The dome may comprise a plurality of layers (10, 12), at least one of which is a layer of a metal or a metal alloy, in intimate contact. This sandwich construction enables an improved frequency response characteristic to be achieved. The metal or metal alloy layer or layers may also be provided with one or more layers of a protective material and/or a sound damping material. A non-metallic filler layer (18) may be provided between two layers (10,12) of metal or metal alloy.

Description

[0001] This invention relates to radiating domes as used in loudspeakers and loudspeaker systems, and is particularly concerned with radiating domes for use in high frequency loudspeakers.

[0002] Conventionally, radiating domes used as the vibrating element in loudspeakers have been made out of soft materials, for example impregnated cloth or plastics materials, or metals, for example aluminium or titanium. Each of these types of dome can be made in various ways. Mechanical forming by pressing or drawing into shape has been used, and more recently a variety of metal deposition techniques have been developed.

[0003] One problem which arises with such radiating domes is that of dissipating the heat which is produced by the associated coil. This is particularly troublesome with treble units when reproducing for example a piece of music which has a sustained high- level output in the top frequency range. Various methods have been proposed in the past to eliminate or mitigate this problem. For example, cooling fluids have been used around the coil as a heat sink. However, these known methods have various disadvantages. In particular, they make the assembly of the unit more complex and time-consuming, and therefore expensive, and they can also adversely affect the frequency response.

[0004] It is an object of the present invention to provide an improved construction of metal dome, especially by using a particular range of metals and metal alloys, by means of which one achieves an improved frequency response characteristic, and an exceptional thermal capability.

[0005] In accordance with one aspect of the present invention there is provided a radiating metal dome for use in loudspeakers and loudspeaker systems which is made out of one or more of the metals selected from the group copper, silver and gold, or out of an alloy of copper, silver or gold with additions not sufficient substantially to reduce the thermal conductivity.

[0006] In accordance with another aspect of the present invention there is provided a radiating metal dome for use in loudspeakers and loudspeaker systems which comprises a plurality of layers, at least one of which is a layer of a metal or a metal alloy, in intimate contact.

[0007] Preferably, the metals or metal alloys in the multiple layer construction are selected from or based upon the group copper, silver and gold.

[0008] In order that the invention may be more fully understood, a number of embodiments of metal dome in. accordance with the invention will now be-described by way of example and with reference to the accompanying drawing, in which:

Fig. 1 is a schematic 'representation of a first embodiment of metal dome made in accordance with the present invention;

Fig. 2 is a similar schematic representation of a second embodiment of metal dome; and,

Fig. 3 is a schematic representation of a third embodiment of metal dome.

[0009] The radiating dome shown in Fig. 1 comprises two layers 10 and 12 which are in intimate contact with each other to form the complete dome structure. Each layer 10, 12 is made of a metal or metal alloy. The material of at least one of the layers, and preferably of both layers, is copper, silver or gold, or an alloy based upon copper, silver or gold with additions which are not sufficient substantially to reduce the, thermal conductivity of the material. If one of the layers lO, 12 is made of such a metal or metal alloy, then the other layer may be made of some other metal or metal alloy, for example bronze, being either a copper/tin alloy or a copper/aluminium alloy.

[0010] The thermal conductivities of the metals copper, silver and gold are given below, and, for comparison purposes, the list includes the thermal conductivity of aluminium.

Silver : 407 W/m K at 20°C.

Copper : 386 W/m K at 20°C.

Gold : 288 W/m K at 20°C.

Aluminium : 204 W/m K at 20°C.

[0011] The dome itself is integral with a cylindrical extension which is made of the same materials and at the same time as the dome and which carries a surrounding coil 14. This cylindrical coil bobbin is provided with an outwardly projecting circumferential flange 16 which serves as a support or seat for the coil 14.

[0012] Although Fig. 1 represents the construction of a double-layer metal dome, the invention also includes a single-layer dome made from copper, silver or gold, or from an alloy of copper, silver or gold with additions not sufficient substantially to reduce the thermal conductivity.

[0013] The preferred overall thickness of the dome is . from 0.05 to 0.1 mm. The construction of such a dome can be achieved using any suitable metal deposition technique, for example vacuum deposition, electrodeposition, RF sputtering, etcetera.

[0014] Fig. 2 shows an alternative embodiment of radiating dome which again includes the two metal or metal alloy layers 10 and 12. However, in this embodiment, the two layers are separated by a filler layer 18 which is continuous with the layers lO and 12. This filler layer 18 can be non-metallic, for example of a synthetic plastics material, or a rubber material for example. This sandwich construction with a filler can produce improved mechanical properties for the dome. In this embodiment of the invention the dome is not provided with an integral circumferential flange to support the coil 14. The coil 14 is secured in place by any suitable conventional means.

[0015] Fig. 3 shows an alternative embodiment in which the dome comprises a single metal layer 10, of a material as specified above, which is protected on both sides by a coating layer 20a, 20b. Although the coating layer is shown as being provided on both sides of the metallic layer 10, it can alternatively be provided on one face only of the dome. The coating layer or layers 20a, 20b perform a protective function, and may suitably be made of a non-metallic material.

[0016] Although not shown in the drawings, an acoustic damping material may be provided on one or both sides of the dome in any of the embodiments described above.

Claims

1. A radiating metal dome for use in loudspeakers or loudspeaker systems characterised in that the dome is made out of one or more of the metals selected from the group copper, silver and gold, or out of an alloy of copper, silver or gold with additions not sufficient substantially to reduce the thermal conductivity.

2. A radiating metal dome for use in loudspeakers and loudspeaker systems characterised in that the dome comprises a plurality of layers (10, 12; 10, 18, 12; 20a, 10, 20b), at least one of which is a layer of metal or a metal alloy, in intimate contact.

3. A radiating metal dome as claimed in claim 2, charatcerised in that said at least-one layer is a metal selected from the group copper, silver and gold or an alloy of copper, silver or gold with additions not sufficient substantially to reduce the thermal conductivity.

4. A radiating metal dome as claimed in claim 2, or 3, characterised by a layer of a protective material (20a, 20b) on at least one side of the dome.

5. A radiating metal dome as claimed in any of claims 2 to 4, characterised by two layers (10, 12) of metal or metal alloy with a non-metallic filler layer (18) therebetween.

6. A radiating metal dome as claimed in any preceding claim, characterised by a sound damping material on at least one side of the dome.

7. A radiating metal dome as claimed in any preceding claim, integral with a coil bobbin-which is formed of the same material at the same time.

8. A radiating metal dome as claimed in any preceding claim, characterised in that the dome is produced using a metal deposition technqiue.

9. A radiating metal dome as claimed in any preceding claim, characterised in that the overall thickness of the dome is from 0.05 to 0.1 mm.

Drawing