JPS58107793

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DESCRIPTION JPS58107793
[0001]
An object of the present invention is to provide a flat plate speaker having a flat plate diaphragm
and capable of reproducing flat sound pressure frequency characteristics up to a high range. In
general, a flat plate spill force having a flat plate diaphragm is configured as shown in FIGS. 1
and 2. In FIGS. 1 and 2, an annular magnet 7, an annular yoke 8 and a center ball 6 constitute a
magnetic circuit having an annular magnetic gap. A cylindrical voice coil 3 is disposed in the
magnetic gap, and an electrical signal is supplied to the voice coil 3 to induce a driving force.
This driving force is transmitted to the flat plate diaphragm 1 via the voice coil bobbin 2 and the
conical or elliptical conical drive cone 4. The end of the diaphragm is fixed via a free edge 9 to a
frame 10 attached to the magnetic circuit. The voice coil bobbin 2 is attached to the frame 10 via
a damper 6 having a wavelike suspension. A flat speaker having such a flat diaphragm. It is often
used to reproduce flat sound pressure characteristics up to the high range. However, when the
vibration mode of the flat plate diaphragm 1 at high frequency is observed, only the portion
where the voice coil bobbin 2 is joined to the flat plate diaphragm 1 as shown by the curve A in
FIG. The amplitude was found to be small. The sound pressure frequency characteristic of this
flat panel speaker is such that a sound pressure valley occurs at a frequency fa (3 to 5 KHz) as
shown by the solid line B in FIG. Was. That is, in the flat plate speaker described above, it was
found that the vibration mode of the flat plate diaphragm 1 vibrates only in the vicinity of the
voice coil joint as shown in FIG. 3 near the frequency at which the sound pressure characteristics
become valleys. For this reason, there is a problem that a valley of sound pressure in the sound
pressure frequency characteristic is generated. The present invention solves the abovementioned conventional drawbacks, and it is a sound wave at a junction between a voice coil
bobbin or a conical drive cone for transmitting a driving force induced to a voice coil to a flat
diaphragm and the flat diaphragm. By attaching a shield that blocks sound waves to the front
side of the flat plate from which sound is emitted, the valleys of the sound pressure on the sound
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pressure frequency characteristics are eliminated to reduce the high frequency banding, and the
flat sound pressure frequency It is intended to reproduce the characteristics. That is, an acoustic
resonant circuit is formed by attaching a shielding plate that blocks an acoustic wave at an
appropriate distance on the front surface of the flat diaphragm.
In this acoustic resonance circuit which portion for a distributed constant circuit by mass, but
which part can not that capacity, the side surface of the shielding plate is open, the acoustic
resonance of the distributed constant part thereof corresponded to the opening Configure the
circuit. Therefore, if the resonance frequency of this resonance circuit is made to coincide with
the valley portion of the sound pressure characteristic, the sound pressure characteristic will
swell. Also, in the region higher than this resonance frequency, the sound insulation effect works
and the sound is blocked. Therefore, high frequency peaks are reduced, and the overall sound
pressure characteristics become flat. Hereinafter, an embodiment of the flat loudspeaker of the
present invention will be described. 6 to 7 show an embodiment of the present invention, and in
FIGS. 1 and 2, the same reference numerals indicate the same components. In FIGS. 6 to 7, the
difference from FIGS. 1 and 2 lies in the front surface of the junction of the voice coil bobbin 2
and the flat plate diaphragm 1 (the portion where the vibration width is largest at high
frequencies). The shield plate 11 having a width W is disposed at an appropriate distance d. As
described above, the space narrowed by the shielding plate 11 and the flat diaphragm 1 serves
as an acoustic circuit. The distance d between the shielding plate 11 and the flat plate diaphragm
1 and the width W of the shielding plate 11 differ depending on the frequency at which the
sound pressure characteristics become valleys, but the plate diaphragm 1 does not touch the
shielding plate 11 at a low frequency band It is necessary. From the experimental results, it was
found that the width W was approximately the same as the diameter of the voice coil 3. The
measurement result of the sound pressure characteristic when the shielding plate 11 is attached
is shown by a dotted line C in FIG. As apparent from FIG. 4, it can be seen that flat sound
pressure characteristics are reproduced. Although this shield plate 11 may be formed by bending
a rectangular flat plate as shown in FIG. 8, it may be a shield plate 11 'having an opening 12 as
shown in FIG. At this time, desired characteristics can be obtained by changing the aperture ratio,
the shape of the apertures, and the like. As described above, according to the present invention,
the flat plate from which a sound wave is emitted at the junction of the voice coil or conical drive
cone for transmitting the driving force induced to the voice coil to the flat diaphragm and the flat
diaphragm. Since a shielding plate for blocking sound waves is attached to the front side of the
diaphragm, the valleys of the sound pressure on the sound pressure frequency physical property
are eliminated to reduce high frequency peaks and reproduce a flatter sound pressure frequency
characteristic. It has the advantage of being able to provide a flat loudspeaker that can be
[0002]
Brief description of the drawings
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[0003]
1 is a top view of a conventional loudspeaker speaker, FIG. 2 is a cross-sectional view of the
loudspeaker, FIG. 3 is a vibration mode diagram of a diaphragm in the high frequency range of
the loudspeaker, and FIG. Comparison curve of the sound pressure frequency characteristics of
the present invention and the sound pressure frequency characteristics of the flat panel speaker
of the present invention, FIG. 6 is a top view showing an embodiment of the flat panel speaker of
the present invention, and FIG. FIG. 7 is a side sectional view of the same speaker, FIG. 8 is a
perspective view of a shielding plate used for the same speaker, and FIG. 9 is a perspective view
showing other than the shielding plate used for the flat panel speaker of the present invention is
there.
1 ······ Flat plate diaphragm, 2 ······· Voice coil bobbin 3 ··· Fist · voice coil 4 ··· Building drive cone 6
······ · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Frame, 11.11 '· · · · · ·
shielding plate. Name of Agent Attorney Nakao Toshio and 1 other person Figure 1 Figure 2
Figure 13 Figure 14 Figure 14 Figure 5 Figure 8 vA Figure 9
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