Abstract:
The disklike diaphragm is made up of an essentially conical plastic film provided with vacuum-formed supporting members which extend up to the disklike radiating layer.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a disk diaphragm for a loudspeaker having an intermediate layer between the disklike radiating layer and the voice coil. 
     Such a diaphragm is known from German Offenlegunschrifft DE-OS No. 29 33 425. 
     A loudspeaker diaphragm must meet two very important requirements: it must be light in order to be able to follow steep signal edges without delay, and it must be stiff in order to follow the signal steadily throughout its area and without being deformed. 
     If the first requirement is not met, the loudspeaker has a poor response to pulses and high audio frequencies. If the second requirement is not met, the electric signals are not converted into precisely corresponding, piston-like movements of the diaphragm, but instead the latter is deformed by partial oscillations. Such deformations cause sound pressure waves which do not correspond to the electric drive signal, i.e., which reproduce the latter in distorted form. Furthermore, partial oscillation causes considerable additional stress in the diaphragm material, and can result in fatigue, and even destruction, of the diaphragm. 
     In order to avoid these disadvantages, it has become common practice to replace the well known and widely used conical paper diaphragm by a disk diaphragm, because the latter&#39;s radiation centers lie in one plane. 
     The known disk diaphragm consists of an essentially truncated-cone-shaped molded part of foamed polystyrene on whose flat front side two films are disposed one on top of the other as a disklike radiating layer. 
     Such a structure is rather complicated and, therefore, expensive to manufacture. 
     SUMMARY OF THE INVENTION 
     It is thus the object of the invention to design a disk diaphragm for a loudspeaker in such a manner that the diaphragm and, hence, the loudspeaker can be produced at low cost. According to the invention, the intermediate layer consists of an essentially conical plastic film provided with supporting members which extend up to the disklike radiating layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention will now be explained in more detail with reference to the accompanying drawings, FIGS. 1 to 5, wherein: 
     FIG. 1 is a cross-sectional view of a loudspeaker with a disk diaphragm in accordance with the invention; 
     FIG. 2 is an exploded view of the loudspeaker of FIG. 1; 
     FIG. 3 shows one embodiment of the conical plastic film; 
     FIG. 4 shows another embodiment of the conical plastic film; 
     FIG. 5 shows another embodiment of the disklike radiating layer; and 
     FIG. 6 shows a modification of the disklike radiating layer. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As can be seen from FIG. 1, the novel disk loudspeaker includes a multitude of parts which are also contained in a loudspeaker having a cone diaphragm, i.e. the permanent magnet system 1 to which the loudspeaker basket 2 is fastened, the voice coil support 3, and the voice coil 4, the spider 5, and the crimped diaphragm suspension 6. The only two parts specific to a loudspeaker with a disk diaphragm are the conical plastic film 7, provided with supporting members 9, and the disklike radiating layer 8. 
     For better illustration, the individual parts of the loudspeaker are shown once again in FIG. 2 in an exploded view. The radiating layer 8 may be a circular disk of foamed polystyrene. In addition, the radiation surface 8&#39; may be flocked with plastic fibers 12 as shown, for example in FIG. 6. By such a step, the movement of the diaphragm is damped. For special applications, the radiating layer 8 may have a multilayer structure which may consist of two outer thin metal (e.g. aluminum) sheets bonded to an intermediate layer, e.g. a layer having a honeycomb structure. 
     FIGS. 3 and 4 show two embodiments of the plastic film 7 provided with supporting members 9. The figures are top views of the plastic film 7 in the direction of the arrow 10 in accordance with FIG. 2. The plastic film provided with the supporting members 9 may also be a conventional plastic cone diaphragm, to which the supporting members 9 are attached, for example glued. However, such a construction is likely to be too costly. It should therefore be more advantageous to manufacture the supporting elements 9 and the plastic film 7 as a single piece. This can be done e.g. by vacuum-forming the two parts simultaneously. 
     In the embodiment illustrated in FIG. 3, the supporting members 9 have a truncated-cone shape which tapers off towards the radiating layer. 
     In the embodiment illustrated in FIG. 4, the supporting members 9 have the form of circular segments. 
     FIG. 5 shows another embodiment of the radiating layer 8, which differs from the above embodiment in that its reverse side is provided with a symmetrical projecting portion 11. If this projecting portion 11 has the proper dimensions, the radiating layer 8 can be centered in a simple manner.