JP2004221880

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DESCRIPTION JP2004221880
An object of the present invention is to solve an increase in unnecessary vibration in a frequency
band exceeding a resonance frequency. A voice coil VC is driven by a first magnetic circuit MA to
vibrate a diaphragm 2, and an actuator coil CA is vibrated by a second magnetic circuit MB. A
second vibration system 15 not including the vibration plate 2 driven in the opposite direction
and a low pass filter 13 having a predetermined frequency as a cutoff frequency, and an output
of the low pass filter 13 is electrically Connected. [Selected figure] Figure 3
Speaker device
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device, and more particularly to a speaker device provided with a vibration system that
vibrates by a magnetic circuit. [0002] A speaker device provided with a vibration system that
vibrates by a magnetic circuit, for example, a moving coil type dynamic speaker is known as a
home or car speaker device. In such a speaker device, when the voice coil is electromagnetically
driven in the magnetic circuit, the voice coil vibrates integrally with the diaphragm and radiates
acoustic energy. In such a speaker device, unnecessary vibration is generated around the
magnetic circuit as a reaction when the diaphragm is driven, so as shown in FIG. 1, it is generated
by the magnetic circuit 101 included in the moving coil type speaker device. A reverse magnetic
circuit 102 generating a magnetic flux opposite to the magnetic flux, and a sub voice coil 103
driven by the magnetic flux generated by the reverse magnetic circuit 102 are provided behind
the magnetic circuit 101 to cancel unnecessary vibration. There is a speaker device (see, for
example, Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 6217391 (FIG. 1) SUMMARY OF THE INVENTION However, the reverse magnetic circuit 102 for
canceling unnecessary vibration is a magnetic circuit 101. The frame 105 is provided on the side
of the diaphragm 104 (cone) driven by the magnetic circuit 101 and the opposite magnetic
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circuit 102 does not have the same frame. The mechanical impedance when looking at the side of
the frame 105 from the side and the mechanical impedance when looking at the side of the
frame 105 from the reverse magnetic circuit 102 differ. Further, above the division frequency of
the diaphragm 104, the mechanical impedance seen from the voice coil of the magnetic circuit
101 and the mechanical impedance of the vibration system seen from the sub voice coil 103 of
the reverse magnetic circuit 102 are different. Therefore, the vibration system of the reverse
magnetic circuit 102 for canceling the unnecessary vibration may cancel the reaction of the
vibration by the magnetic circuit 101 below the resonance frequency generated from the
structure of the speaker unit and the structure of its attachment. Although this can be done, at
frequencies higher than this resonance frequency, the above reaction can not be canceled, and
there is also a frequency band that increases unnecessary vibration. An example of measuring
the effect when the magnetic circuit (corresponding to the reverse magnetic circuit 102) for
canceling the unnecessary vibration is provided as described above is shown in the graph of FIG.
FIG. 2 shows the results of measuring the vibration acceleration of the frame of the speaker
device by changing the frequency of the audio signal in each case with and without a cancellation
magnetic circuit. The resonance frequency generated from the structure of the speaker unit and
the structure of its attachment in the measured speaker device is about 550 Hz. In the graph of
FIG. 2, in the frequency band from 55 Hz to the resonant frequency (about 550 Hz) of the audio
signal, the suppression effect of the vibration acceleration of the frame by the cancel magnetic
circuit can be seen, but the resonant frequency (about 550 Hz) In the above frequency band, the
suppression effect of the vibration acceleration of the frame can not be seen, and conversely, it
can be seen that there is a frequency band in which the vibration acceleration of the frame is
larger than in the case without the cancellation magnetic circuit. The problem to be solved by the
present invention is, for example, to solve the problem that unnecessary vibration increases in
the frequency band exceeding the resonance frequency generated in the above-mentioned prior
art. According to a first aspect of the present invention, there is provided a first vibration system
in which a voice coil is driven by a first magnetic circuit to vibrate a diaphragm, and a second
magnetic circuit. The actuator coil has a second vibration system not including a diaphragm
driven in a direction opposite to the first vibration system, and a low pass filter having a
predetermined frequency as a cutoff frequency, The output of the low pass filter is electrically
connected. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments
according to the present invention will be described in detail based on the drawings. The same or
corresponding components are denoted by the same reference numerals in each embodiment.
First Embodiment FIG. 3 is a block diagram showing a configuration of a speaker device
according to a first embodiment of the present invention, and FIG. 4 is a cross-sectional view
showing an example of a speaker unit 14. As shown in FIGS. 3 and 4, the speaker device 10
according to the first embodiment has a first vibration system 16 that vibrates the diaphragm 2
with the voice coil VC driven by the first magnetic circuit MA. A second vibration system 15 not
including the diaphragm 2 whose actuator coil CA is driven in the direction opposite to the first
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vibration system 16 by the second magnetic circuit MB, and a low pass filter having a
predetermined frequency as a cutoff frequency And 13. The voice coil VC is electrically
connected to the output of the audio signal amplified by the amplifier 11 (first amplifier), and the
actuator coil CA is the audio amplified by the amplifier 12 (second amplifier). The output of the
signal is electrically connected via the low pass filter 13.
In the first embodiment, the amplifier 12 (second amplifier) for driving the actuator coil CA is
separate from the amplifier 11 (first amplifier) for driving the voice coil VC, so the amplification
factor is Can be set with the amplifier. The speaker unit 14 has a first magnetic circuit MA
including a magnet MGa, a plate 9 a and a yoke 1 a, a voice coil VC, and a diaphragm 2 as
components constituting the first vibration system 16. As components constituting the twovibration system 15, there is provided a second magnetic circuit MB consisting of a magnet MGb,
a plate 9b and a yoke 1b, an actuator coil CA, and a weight 4 attached to the rear of the bobbin
6b of the actuator coil CA. Further, the bobbin 6a of the voice coil VC is connected to the frame 3
via the damper 7a, and the diaphragm 2 is connected to the frame outer periphery 3a and the
panel (mounting plate for the speaker unit) 5 via the edge 8 thereof. ing. The bobbin 6b of the
actuator coil CA is connected to the plate of the magnetic circuit MB via the damper 7b. Next, the
operation and operation of the speaker device 10 will be described. FIG. 5 is an explanatory view
of a mechanical circuit that is mechanically equivalent to the speaker unit 14. As shown in FIG. 5,
in the mechanical circuit of the speaker unit 14, the equivalent mass m1 of the frame outer
periphery 3a + panel 5 is connected to the panel compliance Cp, and the equivalent mass m0
serving as the load of the first vibration system 16 (vibration system Speaker edge compliance Ce
between equivalent static mass + air load mass) and equivalent mass m1, frame compliance Cf
between equivalent mass m2 and equivalent mass m1 of magnetic circuit MA + magnetic circuit
MB + frame outer periphery 3a, equivalent mass m2 And the equivalent mass m0, the damper
compliance Cda is present, and the damper compliance Cdb is present between the equivalent
mass m2 and the mass M0 of the weight 4. Here, the mass M0 of the weight 4 is such that the
force Fa applied to the equivalent mass m0 (vibration system equivalent stationary mass + air
load mass) serving as the load of the vibration of the first vibration system 16 balances the force
Fb applied to the mass M0 Set to Then, the operation of the speaker device 10 shown in FIG. 3 is
as follows. In FIG. 3, an external amplifier 11 that amplifies the audio signal and outputs the
amplified audio signal to the speaker device 10 amplifies the audio signal and sends the output
to the voice coil VC of the speaker unit 14.
On the other hand, the internal amplifier 12 amplifies the audio signal and sends its output to the
low pass filter 13. The low pass filter 13 has the lowest resonance frequency (for example, the
lowest resonance frequency) at which the frame compliance Cf, which is equivalent compliance
occurring in the frame 3, and the equivalent mass m2 and equivalent mass m1, which are
equivalent masses before and after the frame compliance Cf And cut the audio ¦ voice signal of
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the frequency band more than about 550 Hz, and let only the audio ¦ voice signal of the
frequency band below this resonance frequency pass. That is, when the frequency of the audio
signal exceeds the resonance frequency, the second vibration system 15 for canceling the
reaction of the speaker unit 14 has a reaction as shown in the graph of FIG. 2 described above.
Since the effect of canceling is eliminated and the unnecessary vibration may be increased on the
contrary, the sound signal exceeding the resonance frequency is cut and only the sound signal
having a frequency lower than the resonance frequency is allowed to pass. Thus, the voice coil
VC constituting the first vibration system of the speaker unit 14 is driven by the output of the
amplifier 11 (first amplifier), and the second vibration system 15 of the speaker unit 14 is It is
driven by the output of the low pass filter 13. Second Embodiment FIG. 6 is a block diagram
showing a configuration of a speaker device according to a second embodiment. As shown in
FIGS. 6 and 4, the speaker device 20 according to the second embodiment has a first vibration
system 16 that vibrates the diaphragm 2 with the voice coil VC driven by the first magnetic
circuit MA. A second vibration system 15 not including the diaphragm 2 whose actuator coil CA
is driven in the direction opposite to the first vibration system 16 by the second magnetic circuit
MB, and a low pass filter having a predetermined frequency as a cutoff frequency And 13. An
output of the voice signal amplified by the voice coil VC and the low pass filter 13 is electrically
connected to the voice coil VC, and an output of the low pass filter 13 is electrically connected to
the actuator coil CA. As described above, the second embodiment can reduce the cost because
only one amplifier is required to amplify the audio signal. The speaker unit 14 in the second
embodiment is configured in the same manner as in the first embodiment, and the operation and
operation thereof are also the same as those described with reference to FIG. 5 described above. .
Third Embodiment FIG. 7 is a block diagram showing a configuration of a speaker device
according to a third embodiment.
As shown in FIGS. 7 and 4, the speaker device 30 according to the third embodiment has a first
vibration system 16 that vibrates the diaphragm 2 with the voice coil VC driven by the first
magnetic circuit MA. A second vibration system 15 not including the diaphragm 2 whose
actuator coil CA is driven in the direction opposite to the first vibration system 16 by the second
magnetic circuit MB, and a low pass filter having a predetermined frequency as a cutoff
frequency And an amplifier 32 with a built-in low pass filter. An output of the audio signal
amplified by the amplifier 11 is electrically connected to the voice coil VC, and an output of the
audio signal amplified by the low-pass filter built-in amplifier 32 is electrically connected to the
actuator coil CA. Connected to As described above, in the third embodiment, since the amplifier
and the low pass filter are integrated, the device can be made smaller. The speaker unit 14 in the
third embodiment is configured in the same manner as in the first embodiment, and the
operation and operation thereof are also the same as those described with reference to FIG. 5
described above. . The structure of the speaker unit 14 in each embodiment is not limited to that
shown in FIG. 4. For example, the magnetic circuit MA of the first vibration system and the
magnetic circuit of the second vibration system It may be a structure having a common MB. The
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low pass filter 13 in each embodiment may be a circuit combining a choke coil, a resistor, a
capacitor, etc., that is, it may be an analog circuit including a choke coil, or may be a digital
circuit. It may be Although the speaker unit 14 described in FIG. 4 is provided with a coneshaped diaphragm, the configuration of the present invention is a dome-shaped or the like if it is
a dynamic speaker unit using a magnetic circuit. It is applicable also to a speaker unit etc. The
amplifiers 11 and 12, the low pass filter built-in amplifier 32, and the speaker unit 14 do not
have to be all housed in the same case. As described above in detail, according to the first
embodiment of the present invention, the first vibration system 16 causes the voice coil VC to be
driven by the first magnetic circuit MA to vibrate the diaphragm 2. And a second vibration
system 15 not including the diaphragm 2 whose actuator coil CA is driven in the direction
opposite to the first vibration system 16 by the second magnetic circuit MB, and a low pass
having a predetermined frequency as a cutoff frequency An output of the low pass filter 13 is
electrically connected to the actuator coil CA.
Thus, in the configuration in which the reaction of the speaker unit 14 caused by the first
vibration system 16 is canceled using the second vibration system 15, the lowest resonance
frequency at which the equivalent mass m2 and the equivalent mass m1 resonate. Since the
frequency band of the audio signal exceeding (for example, about 550 Hz) may increase
unnecessary vibration, it is cut and the second vibration system 15 is not operated in such a
frequency band. Conversely, unnecessary vibration can be prevented from increasing. The
second embodiment and the third embodiment have similar effects. BRIEF DESCRIPTION OF THE
DRAWINGS FIG. 1 is a diagram showing a speaker apparatus configured to cancel a conventional
unnecessary vibration. FIG. 2 is a graph showing the result of measuring the effect when a
magnetic circuit for canceling unnecessary vibration is provided. FIG. 3 is a block diagram
showing a configuration of the speaker device according to the first embodiment. FIG. 4 is a
cross-sectional view showing an example of a speaker unit. FIG. 5 is an explanatory view of a
mechanical circuit that is mechanically equivalent to the speaker unit. FIG. 6 is a block diagram
showing a configuration of a speaker device according to a second embodiment. FIG. 7 is a block
diagram showing a configuration of a speaker device according to a third embodiment.
[Description of the code] 10 speaker device 11 amplifier (first amplifier) 12 amplifier (second
amplifier) 13 low pass filter 14 speaker unit 15 first vibration system 16 second vibration system
32 amplifier with low pass filter
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