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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a conventional speaker, FIG. 2 is
a cross-sectional view thereof, FIG. 3 and FIG. 4 are explanatory diagrams of its driving method,
and FIG. FIG. 6 is a diagram of sound pressure frequency characteristics of the conventional
speaker and the speaker of the present invention, and FIG. 7 is a connection diagram of a voice
coil of the speaker of the present invention. 1 ······· Flat diaphragm, 2 ······························· Voice coil,
11 ··············· Capacitor. 141 ° T
Detailed description of the invention The present invention is also related to a speaker
configured to drive a flat diaphragm by a plurality of voice coils, and the objective is to improve
the pressure frequency characteristics with a simple configuration. It is the purpose. In general, a
speaker using a rectangular flat diaphragm)), tJ = @ ′ ′ 21! JItCyr <f ′ ′ <rKms ° 1 ′ ′ 71
′, in FIG. 2, the rectangular flat diaphragm 1 is supported on the frame 8 by the ENO β and the
9882 2 and the diaphragm 1 has one dovetail 5, A voice coil 3.3 'supported by a damper 4, 4' is
coupled to the magnetic gap of the magnetic circuit consisting of 5 ', magnet 6, 6' and lower
play) 7.7 '. As shown in FIGS. 3 and 4, this voice coil 3 ′ 3 ′ has a vibration mode A at the time
of resonance of the free vibration of the rectangular flat diaphragm 1. It is connected to the
respective clauses A ′ and B ′ ′ ′ of B. The vibration mode A has two nodes A 'and A "as
shown in FIG. 3, and the vibration mode B has four nodes B', BN, B" and B "'. The frequency f of
this vibration mode B is defined as f3. In vibration mode C, as shown in FIG. 3, the nodes C ', C
"IC! This is a non-symmetrical vibration, which is "three", and its frequency is defined as f2. And
the damping material 9 is joined to the position of the maximum amplitude of this vibration
mode C. On the other hand, as shown in FIG. 6, the voice pressure frequency characteristic of the
conventional speaker of such a configuration, in which the voice coil 3.3 'is connected in series
and driven by the AC signal source 10, is shown in FIG. It is shown in the figure. The vibration
modes at resonance frequencies f1 and 98 and f3 are damped by the effect of line drive by voice
coil 3, 3 'and the sound pressure becomes flat, and the asymmetrical mode at resonance
frequency f2 is suppressed by damping material 9 The sound pressure can be expanded to a flat
or even higher-order resonance frequency fH. However, a peak of sound pressure occurs at a
high-order resonance frequency fH, which adversely affects acoustically, causing a problem. The
present invention solves the above-mentioned conventional drawbacks □, and the present
invention will be described with reference to the drawings of the C embodiment. FIG. 7 shows an
embodiment of the present invention. In FIG. 7, a capacitor 11 is connected in parallel to the
voice coil 3 'and a filter is connected between the voice coils 3' and 1 ''. The cut frequency fc is
about 70% of the high-order resonance frequency fH.
In a specific example, when using a voice coil 3.3 'and an 89 voice coil with a diameter of 19
cabinets, and its high-order resonance frequency fH is 2 KHz-), the cond / is 11 becomes about
89 μF 904 If a capacitor 11 is connected to the voice coil 3 'to form a filter, the phase and
amplitude of the current flowing through the voice coil 3', that is, the driving power distribution
is controlled at the peak frequency, and the vibration mode is changed. As a result, as shown by
the broken line in FIG. 6, the sound pressure frequency characteristic can suppress the highorder resonance frequency fH to a low level and flatten it. Although the filter 11 is configured by
inserting the capacitor 11 in the above embodiment, an inductance may be used other than this.
As described above, according to the present invention, in order to remove the sound pressure
peak with a simple configuration in which a passive element such as 1 inductance or capacitance
is inserted into the voice coil, the high-order resonance frequency peak of high voltage frequency
characteristics is suppressed. It has the advantage that it can be planarized.