Diaphragm for a loudspeaker

Details Diaphragm for a loudspeaker Diaphragm for a loudspeaker

1990-01-03

1992-11-10

Fuller, Benjamin R.

Acoustics

Diaphragm

With damping means

181170, H04R 702

Patent

active

051626195

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

In a cone loudspeaker, the rearward end of the diaphragm is connected with the moving coil and, by way of a centering membrane, with the loudspeaker enclosure while its front end is connected with the loudspeaker enclosure by way of a bead. The centering membrane and the bead cause the diaphragm to be mobile as unimpededly as possible in the axial direction of the loudspeaker so as to produce the sound pressure but to be guided in the radial direction of the loudspeaker, i.e. to practically not move at all or as little as possible in this later direction. The diaphragm must here be connected with the bead along its forward circumferential edge.
The tone quality of a loudspeaker is here dependent, inter alia, on the proper functioning of the centering membrane and of the bead, as well as on the behavior of the diaphragm itself.


SUMMARY OF THE INVENTION

It is the object of the invention to configure the diaphragm of a loudspeaker in such a way that, on the one hand, the costs for glueing the diaphragm to the bead are reduced and the tone quality of the loudspeaker is improved.
The above object is generally achieved according to the present invention by a loudspeaker diaphragm which is formed of a two-layer material including a first plastic film, for providing form stabilization, having a second plastic film, for damping partial vibrations, applied or laminated to the first film, and with the diaphragm bean for connecting the diaphragm to a loudspeaker enclosure being a continuation of the same two-layer material. The modulus of elasticity of the first and second films is about 2.10.sup.3 N/mm.sup.2 and 10-500 N/mm.sup.2, respectively, and the thickness of the first and second films is about 200 .mu.m.+-.40 .mu.m and 100 .mu.m.+-.50 .mu.m, respectively.
In the solution according to the invention, the two films which together form the diaphragm, each by themselves perform different tasks. The first film, preferably composed of polycarbonate and having a relatively high modulus of elasticity, takes over the task of providing the required form stability of the diaphragm. It thus gives the diaphragm the stiffness required for distortion-free reproduction. The second, laminated film is configured as a thermal polyurethane film and serves to dampen partial vibrations of the diaphragm. Compared to the first film, it has a significantly lower modulus of elasticity. With such a two-layer diaphragm, requirements for form stability of the diaphragm, on the one hand, and damping of partial vibrations, on the other hand, can be met in such a way that the tone quality of the loudspeaker is improved. The second, thermal film preferably also extends over the outer edge region of the diaphragm and can therefore advantageously be additionally employed to simplify the process of glueing the bead to the diaphragm. The second, thermal film then serves to dampen partial vibrations in the diaphragm region and additionally for a hot sealing process or a hot pressing process in the edge region for fastening the bead to the diaphragm. The diaphragm according to the invention is particularly suitable for a cone loudspeaker in a television receiver.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of embodiments thereof and reference to the drawing figures wherein in:
FIG. 1 is a schematic sectional view showing the structure of a cone loudspeaker;
FIG. 2 is a partial sectional view of the cone diaphragm FIG. 1 at region "A"; and
FIG. 3 is a partial sectional view showing another configuration of diaphragm and bead at region "B" of FIG. 1.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a loudspeaker including an enclosure 1, a magnet 2, a moving coil 3, a centering membrane 4, a conical diaphragm 5 and a bead 6. Centering membrane 4 and bead 6 are each connected with the edge of diaphragm 5 by means of a hot sealing process, a hot pressing process or by ultrasonic welding. The inner edge of centering membrane 4 is connected with moving coil 3 and the outer ed

REFERENCES:
patent: 3093207 (1963-06-01), Bozak
patent: 3285364 (1966-11-01), Cohen
patent: 4140203 (1979-02-01), Niguchi et al.
patent: 4190746 (1980-02-01), Harwood et al.

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