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DESCRIPTION JPS577284
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing the structure of
a back cover of a general horn-type speaker driving unit, FIG. 2 is an enlarged cross-sectional
view of a portion shown in FIG. It is sectional drawing which takes out, expands and shows one
part in one Example of the back cover of the horn type speaker drive part of this invention. 3 · · · ·
· · back cover, 3a, 3b · · · · · · · · thin plate, 3C · · · · · · · · · visco-elastic substance.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a back cover for a
horn type speaker driving portion formed by using a three-layer structure IIi in which a
viscoelastic material is contained in the darkness of two thin plates. FIG. 1 is a cross-sectional
view showing the configuration of the back cover of a general horn type speaker drive part, and
the lFi diaphragm in FIG. 1 FIG. 2F1 back cavity, 3 is a bank surrounding the diaphragm it and
forming a back cavity It is a cover. The back cover 3 is conventionally made of a single material,
i.e., aluminum die-casting, as shown in No. 2 of the prior art. In the case of using such an
aluminum die cast having the wedge 2 鮪 at a portion shown by P-IA in FIG. It is necessary to
lose strength and strength, and to have a wall thickness of Pl-(t). For this reason, it is Klk if a
large volume 1n7i forms a good back cavity. Also, even when raised, the vibration occurred at the
inherent resonance point, and the reaction adversely affected the diaphragm. This device is
considered in view of the above points, and is formed by a three-layer structure in which a viscoelastic substance is sandwiched between two thin plates, and mechanical resonance excited by
sound pressure of the horn is suppressed, which is favorable. It is an object of the present
invention to provide a horn type speaker driving so pack cover which is apt to obtain reproduced
sound. Hereinafter, an embodiment of the back cover of the horn type speaker cage according to
the present invention will be described with reference to the drawings. FIG. 3 is an enlarged cross
section of one embodiment. FIG. 3 is an enlarged cross-sectional view of the portion
corresponding to the circle AK @ in 1 mK. 3 m and 3 b in FIG. 3 are 2 '! It is a thin plate such as a
metal plate of X or a synthetic tree (2) finger plate. This two thin plates 3m. Viscoelastic
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substance 3C is entrapped between 3b. As the two thin plates 3m and 3b, steel plates, M-plates,
acrylics, phenolic resin cages, etc. are used, and when it is made of visco-elastic substance 3C, for
example, complete-Krill pressure-sensitive adhesive etc. Is used. As described above, although the
back cover 3 is formed as a three-layered structure plate in which the visco-elastic substance 3C
and two thin plates 3m and 3b are sandwiched, as an example used in this invention, The
longitudinal elastic modulus and internal loss of a thin plate 3a-viscoelastic 3C-thin plate 3b
three-layer structure (Fe-D (dumping material) -Fe three-layer structure) are shown in
comparison with materials of aluminum and synthetic resin, As shown in Table 1 below, we can
see that the internal loss is extremely large compared to other materials, (3) <!
1) □ As mentioned above, if the back cover VC of the horn type speaker drive unit of this
invention is a viscose with a thin plate of v2 sheets such as a metal cover or a synthetic finger
plate, the back cover itself is a visco-elastic material &! ５１！ With a three-layer structure board,
the vibration of the back cover can be reduced, and the thickness of the back cover can be made
thin. Therefore, with the same external dimensions as K, the back cavity can be carried out by six
persons. Anyway, it is possible to suppress mechanical collisions excited by the sound pressure of
the horn and obtain O-reproduction sound up to a good bass. The simple JIL description IEI- of
this drawing is a cross-sectional view showing the configuration of the back cover of a general
horn-type speaker drive unit, an enlarged cross-sectional view of the portion shown in FIG. The
back cover of the horn-type speaker driving unit according to the invention is the same
protrusion Jl [llell K] as shown in FIG. 3 · · · Back cover 3m, 3b · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
························································································
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 728 "" mMA / i 4 "4 ° 1"
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