Loudspeaker diaphragm

DETAILED DESCRIPTION What is claimed is: 1.
A plane-type or cone-type loudspeaker diaphragm with a foam material having an inclined surface formed to shape a frustum of a cone, said cone having an inward step provided therein about the thickness of a bobbin near the middle of the inclined surface such that the bobbin for accurately positioning said diaphragm with respect to a voice coil can be easily attached to said diaphragm correctly.
2.
The diaphragm of claim 1 wherein said bobbin is generally shaped conically.
3.
The diaphragm of claim 2 having a back surface which is generally shaped conically.




Description:
This invention relates to an improved diaphragm for a plane-type loudspeaker.
There have been plane-type loudspeakers which use the frame and magnetic circuit of a cone-type loudspeaker but the front surface of which is made planar by using a foam material to fill the space where a cone-shaped diaphragm would be.
An example of such plane-type loudspeaker is illustrated in FIG.
1 wherein a field system section 5 comprising a plate 2 with a center pole 1, an annular magnet 3 made of ferrite and an annular plate 4 is connected to a frame 6, and an edge piece 7 and the peripheral section of a diaphragm 8 shaped like a frustum of a cone and filled with a foam material are connected to the periphery of this frame 6.
There is a bobbin 9 connected to this diaphragm 8 in the middle section on the backside, and this bobbin 9 is supported at the center by a damper 11 so that it is correctly positioned with respect to the magnetic gap 12 of the field system section 5 of a voice coil.
It is very difficult, however, to install the bobbin 9 accurately at the center of the back surface of the diaphragm 8.
For this reason, it was necessary, for example, to use an apparatus 13 shown in FIG.
2 having an inner diameter which is identical to the outer diameter of the diaphragm 8 and a protruding section 13a which is slightly larger than the center pole.
When the diaphragm 8 and the bobbin 9 are attached together, they are placed inside this apparatus 13 for drying