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JPH05183980

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DESCRIPTION JPH05183980
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
motional feedback (hereinafter referred to as "MFB") speaker apparatus provided with a passive
radiator in order to improve bass reproduction capability.
[0002]
2. Description of the Related Art In recent years, it has been desired to improve characteristics
such as high sound quality, high output, and expansion of a bass region with the digitization of
audio output equipment in the speaker device, and an MFB speaker device is conventionally used
for this application. ing. Hereinafter, a conventional MFB speaker device will be described.
[0003]
FIG. 4 is a block diagram showing an example of a conventional MFB speaker device. As shown in
the figure, an audio signal from an audio input signal source 1 is amplified by a power amplifier
2 and given to a phase inversion type speaker 3. The phase inversion type speaker 3 has a
speaker unit 5 and a bass reflex port 6 opened at the lower part of the mounting surface in the
phase inversion cabinet 4, and is a speaker capable of reproducing bass with a relatively small
internal volume. The bass reflex port 6 emits the phase-reversed sound radiated from the rear
surface of the diaphragm of the speaker unit 5 to emphasize the bass range.
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[0004]
A detector 7 is attached to the dust cap of the diaphragm of the speaker unit 5. The detector 7 is
a sensor that detects the vibration acceleration of the speaker unit 5 and converts it into a
voltage, and the output thereof is given to the feedback circuit 8. The feedback circuit 8
generates an acceleration signal output from the detector 7, a velocity signal obtained by
integrating the acceleration signal, and a position signal (amplitude) obtained by further
integrating the velocity signal, and changes the gains and phases of these signals. It is a circuit
that outputs a feedback signal. The output of the feedback circuit 8 is provided to the power
amplifier 2 as a negative feedback signal.
[0005]
In the MFB speaker apparatus having such a configuration, the amplitude and phase of the audio
signal input to the power amplifier 2 are controlled so that resonance or anti-resonance is
suppressed at each specific portion of the reproduction frequency, and the reproduction
characteristics in the low band portion While compensating for the distortion of the high
frequency part. FIG. 5 is a diagram showing the frequency characteristic of the speaker unit 5
alone and the resonance frequency characteristic of the bass reflex port 6. The solid line A shows
the frequency characteristic of the speaker unit 5 itself, and the vibration drops sharply around
50 Hz. Curve B shows the resonance frequency characteristic of the cabinet 4 having the bass
reflex port 6 and has a resonance peak near 50 Hz.
[0006]
However, in such a conventional configuration, the air vibration in front of the speaker unit 5 can
be detected by the detector 7 attached to the diaphragm of the speaker unit 5, but from the bass
reflex port 6 The emitted air vibration could not be detected. Therefore, when MFB is applied to
the phase inversion type speaker 3 composed of the speaker unit 5 having frequency
characteristics as shown in FIG. 5 and the bass reflex port 6, the phase of the speaker unit 5
becomes unstable at the antiresonance frequency (around 50 Hz). Become. That is, when a
feedback signal is generated by the feedback circuit 8 by the output of the detector 7, the
feedback signal may be in the same phase where it should be in the opposite phase at the input
of the power amplifier 2. This causes a problem that MFB control in the vicinity of this frequency
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becomes unstable. Furthermore, there is also a problem that distorted sound such as wind noise
from the bass reflex port 6 is generated.
[0007]
The present invention has been made in view of such conventional problems, and in the phase
inversion type speaker, the antiresonance frequency of the speaker unit 5 when the MFB is not
applied matches the resonance frequency of the bass reflex port 6 However, it is an object of the
present invention to realize an MFB speaker device which can stably apply MFB and is excellent
in low frequency characteristics with little distorted sound.
[0008]
The invention according to claim 1 of the present application corrects the low frequency
characteristics of the audio output of an input signal source and a phase inversion type speaker
including a speaker unit and a passive radiator attached to a cabinet. A characteristic correction
circuit, a power amplifier for amplifying the power of the output of the characteristic correction
circuit to drive a speaker unit, a detector attached to a diaphragm of a passive radiator to detect
its vibration, an amplitude of an output signal of the detector, And a feedback circuit that
generates a feedback signal based on the phase and provides the feedback signal to the power
amplifier.
[0009]
The invention according to claim 2 of the present application is a phase inversion type speaker
including a speaker unit and a passive radiator attached to a cabinet, a characteristic correction
circuit for correcting low frequency characteristics of audio output of an input signal source, and
a characteristic correction circuit. Power amplifier for amplifying the power to drive the speaker
unit, first detector and second detector attached to the speaker unit and the diaphragm of the
passive radiator for detecting its vibration, and the first detection The feedback signal is
generated based on the amplitude and phase of the output signal of the second detector, and the
feedback signal is generated based on the amplitude and phase of the output signal of the And a
second feedback circuit that generates and provides the feedback signal to the power amplifier.
[0010]
According to the present invention having such a feature, the sound signal from the input signal
source is corrected by the characteristic correction circuit for the sound pressure in the low
frequency range, and is applied to the power amplification circuit.
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When the power amplification circuit drives the speaker unit, the detector detects the vibration
of the diaphragm of the speaker unit or passive radiator.
The feedback circuit then generates a feedback signal based on the amplitude and phase of the
detector output signal and provides it to the power amplifier.
The feedback signal output from the feedback circuit and the original audio signal are
synthesized, and the power amplifier outputs a drive signal of the speaker unit whose bass range
has been corrected. As a result, the bass reproduction limit frequency of the speaker is expanded,
and feedback is applied to the harmonic components, so that the harmonic distortion is also
reduced in the high-tone reproduction frequency band. Also, passive radiators emit sound waves
from a wide cross-sectional area.
[0011]
A first embodiment of the present invention will be described with reference to the drawings. FIG.
1 is a block diagram showing the configuration of an MFB speaker apparatus according to a first
embodiment of the present invention. In the figure, the input signal source 1, the power amplifier
2 and the speaker unit 5 are the same as those in the prior art. A characteristic correction circuit
9 is provided between the input signal source 1 and the power amplifier 2. The characteristic
correction circuit 9 corrects the frequency characteristic of the audio input signal, and in
particular is a circuit for emphasizing the audio signal in the low frequency band shown in FIG.
The phase-reversal speaker 10 differs from the prior art in that the speaker unit 5 is mounted on
the phase-reversing cabinet 11, and the passive radiator 12 is mounted at the lower opening of
the mounting surface. The passive radiator 12 is a diaphragm having no drive coil, and is a
substitute for the bass reflex port 6 of FIG. 4 and can prevent a dip due to a standing wave. A
detector 13 is attached to the diaphragm of the passive radiator 12. The detector 13 detects the
vibration acceleration of the diaphragm, and its output is given to the feedback circuit 14.
[0012]
If the detector 13 detects, for example, the acceleration of the diaphragm of the passive radiator
12 as in the feedback circuit 8 of FIG. 4, the feedback circuit 14 further includes an acceleration
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signal, a velocity signal obtained by integrating the acceleration signal, and a velocity signal It is
a circuit that generates integrated position signals (amplitudes), changes the gains and phases of
these signals, and outputs feedback signals. The output of the feedback circuit 14 is provided to
the power amplifier 2 as a negative feedback signal.
[0013]
In the MFB speaker apparatus having such a configuration, the difference in the frequency
characteristic of the phase inversion type speaker 10 according to the presence or absence of the
feedback of the signal of the detector 13 attached to the passive radiator 12 is shown in FIG.
Curve C shows the frequency characteristics when the MFB of the MFB speaker 10 is not applied.
A curve D shows the frequency characteristics when MFB is applied without using the
characteristic correction circuit 9, and a curve E shows frequency characteristics when MFB is
applied using the characteristic correction circuit 9.
[0014]
When MFB feedback is not applied, a peak occurs in the frequency band of 100 to 200 Hz as
shown by curve C, but when feedback is applied, as shown by curve D, it is flat at an ultra low
frequency band of 150 to 50 Hz. Sound pressure characteristics can be obtained. This is because
the acceleration of the diaphragm of the speaker unit 5 and the passive radiator 12 is controlled
to be constant by negatively feedbacking the acceleration of the passive radiator 12 to the power
amplifier 2 of FIG. That is, by increasing the effective vibration mass of the passive radiator 12,
the bass reproduction limit is expanded.
[0015]
As described above, according to the present embodiment, by applying MFB, the bass
reproduction limit frequency of the speaker is expanded, and feedback is also applied to the
harmonic components, so that harmonic distortion in the high sound reproduction area can be
reduced. Also, by using a passive radiator instead of the bass reflex port, not only distortion noise
such as wind noise generated from the bass reflex port is eliminated, but also sound waves can
be emitted from a wider cross-sectional area compared with the bass reflex port. You can get a
bass with a sense of volume.
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[0016]
An MFB speaker apparatus according to a second embodiment of the present invention will be
described. FIG. 3 is a block diagram showing the configuration of an MFB speaker apparatus
according to a second embodiment of the present invention. In the figure, the input signal source
1, the power amplifier 2, the phase inversion type speaker 10, and the characteristic correction
circuit 9 are respectively the same as those of the first embodiment, and the description thereof
will be omitted. Unlike the first embodiment, the speaker unit 5 and the passive radiator 12
attached to the cabinet 11 are respectively provided with a first detector 13a and a second
detector 13b for detecting the vibration. The detectors 13a and 13b are the same as the detector
13 shown in FIG.
[0017]
The outputs of the detectors 13a and 13b are applied to a first feedback circuit 14a and a second
feedback circuit 14b. Similar to the feedback circuit 14 shown in FIG. 1, the feedback circuits 14a
and 14b respectively generate an acceleration signal output from the detectors 13a and 13b, a
velocity signal obtained by integrating the acceleration signal, and a position signal obtained by
further integrating the velocity signal. It is a circuit which changes the gain and phase of these
signals and outputs a feedback signal. The outputs of feedback circuits 14 a and 14 b are
summed and provided to power amplifier 2.
[0018]
As described above, in the sound pressure frequency characteristics of only the speaker unit 5 of
the phase inversion type speaker 10 when MFB is not applied, a sharp drop in sound pressure of
the speaker unit 5 occurs at the same portion as the resonant frequency of the passive radiator
12 Even in some cases, the acceleration signals of the speaker unit 5 and the passive radiator 12
are processed and returned together. Then, the change in phase of the passive radiator 12 is
detected by the detector 13b, so that the rapid change in phase of the speaker unit 5 and the
passive radiator 12 can be suppressed, and the frequency characteristic at MFB can be made flat.
[0019]
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In the first and second embodiments, the detectors 13, 13b and 13a respectively detect the
accelerations of the passive radiator 12 and the speaker unit 5, but these detectors may be the
velocity, the amplitude or the diaphragm of the diaphragm. These combined signals may be
detected. If the detector is a sensor that detects the speed of the diaphragm, it is effective to
increase the damping of the speaker unit 5 equivalently. If the detector is a sensor that detects
the amplitude, the suspension of the speaker unit 5 is equivalent. It is effective when you want to
make it harder.
[0020]
As described above, according to the present invention, it is possible to expand the bass
reproduction limit frequency of the speaker device and to reduce the harmonic distortion in the
high-tone reproduction region. In particular, even if the sound pressure frequency characteristics
of the speaker unit when MFB is not applied drop sharply near the resonance frequency of the
bass reflex port or the passive radiator, if the vibration of the passive radiator is detected and a
feedback signal is given to the power amplifier, The abrupt phase change of the diaphragm of the
speaker unit can be suppressed to stabilize the MFB feedback characteristic. Furthermore, by
providing a passive radiator, sound waves can be emitted from a wide cross-sectional area, so
that an advantageous MFB speaker device having a sense of acoustic sensitivity can be realized.
[0021]
Brief description of the drawings
[0022]
1 is a block diagram showing the configuration of the MFB speaker apparatus in the first
embodiment of the present invention.
[0023]
2 is a graph showing the sound pressure frequency characteristics of the first embodiment of the
present invention and the conventional MFB speaker device.
[0024]
<Figure 3> It is the block diagram which shows the constitution of the MFB speaker device in
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2nd execution example of this invention.
[0025]
4 is a block diagram showing an example of a conventional MFB speaker apparatus.
[0026]
FIG. 5 is a graph showing the sound pressure frequency characteristics of the phase-reversal type
speaker unit and the bass reflex port or the passive radiator when MFB is not applied.
[0027]
Explanation of sign
[0028]
1 input signal source 2 power amplifier 5 speaker unit 9 characteristic correction circuit 10
phase inversion type speaker 11 cabinet 12 passive radiators 13, 13a, 13b detectors 14, 14a,
14b feedback circuit
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