JPS57148988

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DESCRIPTION JPS57148988
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a half sectional view of a conventional speaker,
FIG. 2 is a half sectional view showing one embodiment of the present invention, and FIG. 3 is an
output sound pressure characteristic diagram. - 10 ...... diaphragm 10a ...... inner diaphragm, 10b
...... outer diaphragm, 11 ...... voice coil, 12.13 ... · · Fixing ring.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a loudspeaker
having a circular drive part, and a diaphragm being provided on the inside and the outside of the
drive part, and having flat output sound pressure characteristics. It provides a speaker. FIG. 1
shows a half sectional view of a conventional speaker. The diaphragm 1 is composed of an inner
diaphragm 1a formed of a part of a conical shape having an apex angle θ of the cross section
and an outer diaphragm 1b formed of a part of a cone having the same apex angle θ of the cross
section). It is driven by the voice coil 2 with the portion of the apex angle of the tiger r2 + -5 as
the center of the diaphragm. The inner end of the inner diaphragm 1a is fixed to the magnetic
circuit 4 by the fixing ring 3, and the outer diaphragm 1b is similarly fixed to the other position
of the magnetic circuit 4 by the fixing ring 6. ing. In the above-described conventional speaker
configuration, the natural frequency of each of the inner diaphragm 1a and the outer diaphragm
1b is largely different, so that the phase of vibration is different. Sound pressure characteristics
will be disturbed. The broken line m in FIG. 3 shows the result of measuring the output sound
pressure characteristic of this conventional speaker, and at the frequency to +, the inner
diaphragm 1a and the outer diaphragm 1b vibrate in a mode close to opposite phase, It can be
seen that there are 11 large valleys in the characteristic curve. In the above configuration, such
disturbances in characteristics always occur, making it difficult to obtain a flat output sound
pressure characteristic. The present invention solves the above-mentioned conventional defect,
and realizes a flat output sound pressure characteristic speaker by making the cross-section 092
"-1 apex angle of each of the inner diaphragm 11L and the outer diaphragm 1b different. It is
something to try. Hereinafter, an embodiment of the sewage system will be described with
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reference to the drawings. ′\。 FIG. 2 is a half sectional view of the speaker of this
embodiment. ゝ -1-10 is a vibration composed of an inner diaphragm 101L constituted by a part
of a conical shape having an apex angle of θ1 and an outer diaphragm 10b constituted by a
portion of a conical shape having an apex angle of 02 It is a board. Reference numeral 11
denotes a voice coil for driving the above-mentioned apex portion. The inner end of the inner
diaphragm 101L and the outer end of the outer diaphragm 10b are fixed at predetermined
positions of the magnetic circuit portion 14 by fixing rings 12.13. In the above configuration, the
apex angle of the cross section is θ1> θ2, whereby the natural frequency of the outer
diaphragm 10b becomes large, and these θ1. It is possible to make it approximately equal to the
natural frequency of the inner diaphragm 10 & by appropriately selecting the value of θ2.
Therefore, as shown by a solid line B in FIG. 3, a speaker having a flat output sound pressure
characteristic without large valleys can be obtained.
)1. In FIG. 2, .phi.2 / 2 is the support radius of the fixed ring 12 by 093, .phi.2 / 2 is the
support # -small by the fixed ring 13, and .phi.0 / 2 is one drive radius. As is apparent from the
following Example 1, the present invention has an imaging plate on which the inner and outer
peripheral portions are respectively supported and fixed, and a drive portion coupled to the
diaphragm, and the imaging operation is performed. The plate is formed by a part of a conical
surface having an apex angle of 02 and an internal 1 + 111 oscillating portion formed by a part
of a conical surface having an apex angle of 01 inside the one driving portion and an I actuator.
By making the cross section apex angle to be 01> · 02, the characteristic vibration plates of the
inner and outer vibration portions can be made substantially equal, and the output single
pressure characteristic is flat. To provide an excellent speaker that can be
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