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JP2008113102

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DESCRIPTION JP2008113102
In a MFB speaker system, even when an arbitrary amplifier can be selected, it is possible to easily
set a feedback amount suitable for the selected amplifier. An MFB speaker system 100 multiplies
a detection signal related to driving of a speaker 20 driven based on an output signal from a
power amplifier 10 that amplifies an input signal with a gain Ga, and multiplies the detection
signal by a gain β to feed back the input signal. The feedback circuit 30 and a gain control unit
50 that automatically sets the gain index value of the feedback circuit 30 according to the power
amplifier 10 and adjusts the gain β of the feedback circuit 30 based on the gain index value.
[Selected figure] Figure 2
Motional feedback speaker system
[0001]
The present invention relates to a speaker device, and more particularly, to a motional feedback
system for controlling the motion of a vibration system by causing a signal proportional to the
motion of the vibration system of the speaker to be fed back to an amplifier controlling the
motion of the vibration system. The present invention relates to a speaker apparatus of the Back:
MFB type.
[0002]
MFB is intended to improve the characteristics of the poorest performance speaker in the system
by feedback, and more research has been done than before.
[0003]
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1
For example, Patent Document 1 discloses a configuration in which, in an MFB speaker device,
the amount of feedback given to the amplifier can be manually changed in order to adjust the
characteristics of the speaker device and the user's favorite tone.
[0004]
Further, in Patent Document 2, in the MFB type speaker device, in order to control the frequency
characteristics of the speaker according to the reproduced sound level, the feedback amount of
the feedback circuit is adjusted according to the reproduced sound level or the magnitude of the
input signal level. It is disclosed to control.
[0005]
By the way, in the speaker system of the MFB system, it is desired that the user can freely select
the amplifier.
However, in Patent Document 1 and Patent Document 2, making the amplifier replaceable is not
assumed.
[0006]
According to Patent Documents 3-5, in the MFB speaker system, a dual voice coil speaker unit is
used in order to use an amplifier owned by the user or allow the user to freely select an
amplifier. There is disclosed an MFB speaker system configured to add an acoustic signal output
from an amplifier owned by a user to a coil and feed back a signal proportional to the vibration
of a diaphragm to the other voice coil.
[0007]
JP-A-2004-200934 JP-A-62-206999 JP-A-2000-102090 JP-A-2000-270393 JP-A-2000287293
[0008]
As in Patent Literatures 3-5, in the MFB speaker system capable of selecting an arbitrary
amplifier, it is necessary to adjust the feedback amount according to the characteristics of the
amplifier.
08-05-2019
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[0009]
However, it may be difficult for the user to adjust the feedback amount according to the
characteristics of the amplifier.
[0010]
An object of the present invention is to make it possible to easily set an amount of feedback
suitable for a selected amplifier, even when an arbitrary amplifier can be selected in an MFB
speaker system.
[0011]
A motional feedback speaker system according to the present invention multiplies a detection
signal related to driving of a speaker driven based on an output signal from a replaceable power
amplifier that amplifies an input signal by gain β and feeds it back to the input signal. A
feedback circuit, an index value setting unit that automatically sets a gain index value of the
feedback circuit according to the power amplifier, a gain adjustment unit that adjusts the gain β
of the feedback circuit based on the gain index value; And the like.
[0012]
According to one aspect of the motional feedback speaker system of the present invention, the
index value setting unit includes an input operation unit that receives an input of identification
information of a power amplifier, and the identification information input from the input
operation unit. And setting a gain index value of the feedback circuit according to.
[0013]
According to one aspect of the motional feedback speaker system according to the present
invention, the index value setting unit includes a memory for storing a gain index value
corresponding to identification information of a power amplifier, and is input from the input
operation unit. A gain index value corresponding to the identification information is read from
the memory, and the read gain index value is set as a gain index value of the feedback circuit.
[0014]
According to one aspect of the motional feedback speaker system of the present invention, the
motion feedback speaker system further includes a detection unit that detects an output signal
level of the power amplifier, and the index value setting unit is configured to operate when the
feedback circuit is in an inactive state. The gain index value is set on the basis of the relationship
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between the input signal of and the output signal level from the power amplifier corresponding
to the input signal detected by the detection unit.
[0015]
According to one aspect of the motional feedback type speaker system according to the present
invention, the index value setting unit, when the feedback circuit is in the OFF state, has a
frequency equal to or higher than the lowest resonance frequency of the speaker and can
feedback the feedback circuit. The gain index value is set based on the signal level of the output
signal from the power amplifier according to the input signal So having a frequency in a
frequency band, and the gain adjustment unit is configured to turn on the feedback circuit. The
gain β of the feedback circuit is adjusted based on the comparison between the signal level of
the output signal from the power amplifier according to the input signal So and the gain index
value.
[0016]
According to one aspect of the motional feedback speaker system of the present invention, the
index value setting unit responds to an input signal So ′ having a frequency outside the
frequency band to which the feedback circuit can feedback. Setting the gain index value on the
basis of the signal level of the output signal from the signal processing unit, the gain adjustment
unit, when the feedback circuit is in the ON state, has a frequency equal to or higher than the
lowest resonance frequency of the speaker and can feedback the feedback circuit. The gain β of
the feedback circuit is adjusted based on a comparison between the signal level of the output
signal from the power amplifier and the gain index value according to the input signal So having
a frequency in a frequency band. .
[0017]
According to one aspect of the motional feedback type speaker system according to the present
invention, the index value setting unit, when the feedback circuit is in the OFF state, has a
frequency equal to or higher than the lowest resonance frequency of the speaker and can
feedback the feedback circuit. A gain index value is set based on an output sound of the speaker
according to an input signal So having a frequency in a frequency band, and the gain adjustment
unit is responsive to the input signal So when the feedback circuit is on. It is characterized in that
the gain β of the feedback circuit is adjusted based on the comparison between the output
sound of the speaker and the gain index value.
[0018]
According to one aspect of the motional feedback type speaker system according to the present
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invention, the index value setting unit, when the feedback circuit is in the OFF state, has a
frequency equal to or higher than the lowest resonance frequency of the speaker and can
feedback the feedback circuit. Signal adjustment for adjusting the signal level of the input signal
So such that the signal level of the output signal from the power amplifier according to the input
signal So having a frequency within the frequency band matches the predetermined first
reference signal level A second reference signal level determined by the relationship between the
input signal So adjusted by the signal adjustment unit and the first reference signal level is set as
the gain index value, and the gain adjustment unit is configured to When the feedback circuit is
in the on state, the output from the power amplifier according to the adjusted input signal So
Based on the comparison between the signal level and the second reference signal level, and
adjusts the gain β of the feedback circuit.
[0019]
According to one aspect of the present invention, it is possible to automatically set the gain index
value of the feedback circuit according to the power amplifier and adjust the gain β of the
feedback circuit based on the gain index value. In the speaker system, even when any amplifier
can be selected, the feedback amount suitable for the selected amplifier can be easily set.
[0020]
An embodiment specifically showing the best mode for carrying out the present invention will be
described below using the drawings.
[0021]
First, the basic principle of the present embodiment will be described with reference to FIG.
FIG. 1 is a diagram showing a basic configuration of the MFB speaker system in the present
embodiment.
In the MFB speaker system 100, a power amplifier 10 for amplifying an input signal by
multiplying the input signal by a gain Ga, a speaker 20 for driving according to an output signal
of the power amplifier 10 and outputting sound, and a speaker 20 Sensor 22 for outputting a
signal according to motion information such as acceleration and velocity in the vibration system
of the above, a feedback circuit 30 for multiplying the signal output from the vibration sensor 22
by a predetermined gain .beta. 30 includes an auxiliary amplifier 32 which corrects the gain
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which is lowered by incorporating the system 30 into the system 100.
[0022]
In the MFB speaker system configured as described above, the total gain Go representing the
overall sound pressure characteristic is Ga for the gain of the power amplifier 10, Gs for the gain
of the vibration sensor 22, and β for the gain of the feedback circuit 30 Assuming that the gain
of the amplifier 32 is Gh, it is expressed by the following equation (1).
Go = GaGh / (1 + Ga.Gs.Gh..beta.) (1)
[0023]
In the MFB speaker system, the total gain Go is ideally ideally equal to the gain Ga of the power
amplifier, and the adjustment of the total gain Go is conventionally performed by adjusting the
gain β of the feedback circuit.
[0024]
However, bringing the total gain Go close to the gain Ga by adjusting the gain β requires
specialized knowledge and experience, and may be difficult for the user.
Furthermore, when the MFB speaker system is configured to be able to use an arbitrary power
amplifier, the gain Ga of the power amplifier also fluctuates, making it more difficult to adjust the
gain β.
[0025]
So, in this embodiment, in the MFB type speaker system which can use arbitrary power
amplifiers, the gain index value used as the index at the time of adjustment of gain beta is set up
according to a power amplifier.
[0026]
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FIG. 2 is a diagram showing the configuration of the MFB speaker system 100 in the present
embodiment.
In FIG. 2, the frequency characteristic correction unit 40 adjusts the gain for the frequency
outside the frequency band that can be fed back in the feedback circuit 30, and corrects the
frequency characteristic of the system 100 as a whole to be flat.
Here, the frequency band which can be fed back is a band determined by the characteristics of
the speaker and the vibration sensor.
That is, the amplitude of the vibration system of the speaker decreases in proportion to the
square of the frequency of the output signal of the power amplifier.
Therefore, when the frequency of the output signal becomes high to a certain extent, the
vibration sensor can not detect the amplitude of the vibration system of the speaker.
Therefore, the above-mentioned frequency band that can be fed back is a frequency band that
can detect the amplitude of the vibration system of the speaker, and is a band determined in
advance by the characteristics of the vibration system of the speaker or the vibration sensor.
On the other hand, the frequency outside the frequency band that can be fed back refers to the
frequency of the high frequency band where the amplitude of the vibration system of the speaker
can not be detected or the frequency that does not need to be fed back from the characteristics
of the speaker.
[0027]
The auxiliary amplifier 32 amplifies the input signal input through the frequency characteristic
correction unit 40 by multiplying it by the gain Gh, and corrects the overall gain Go of the entire
system 100, which is lowered by incorporating the feedback circuit 30 into the system 100. Do.
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The power amplifier 10 amplifies an input signal input through the auxiliary amplifier 32 and
outputs the amplified signal to the speaker 20.
The speaker 20 is driven based on the input signal from the power amplifier 10 to output sound.
As the speaker 20, for example, by applying an electromagnetic drive to the voice coil in a
magnetic circuit, a vibration system configured by integrating the voice coil with the diaphragm
is moved, and a dynamic speaker that reproduces the sound based on the input signal Etc.
[0028]
The vibration sensor 22 detects drive information such as acceleration and velocity in a vibration
system of the speaker 20, and outputs a detection signal according to the detected drive
information.
As the vibration sensor 22, for example, a sensor that generates a voltage proportional to the
speed of the vibration system can be used as a detection coil attached to the vibration system
moves in the magnetic field.
Alternatively, a sensor may be used which detects a change in capacitance between the movable
electrode and the fixed electrode attached to the vibration system as a voltage signal.
The feedback circuit 30 adjusts the signal output from the vibration sensor 22 with the gain β
and outputs it as a feedback signal.
The drive sensor 22 only needs to output a detection signal related to the drive of the vibration
system of the speaker 20, and is not limited to the above sensor.
[0029]
Now, in the present embodiment, since it is possible to incorporate an arbitrary power amplifier,
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the gain Ga of the power amplifier 10 differs depending on the amplifier selected by the user.
Since the gain Ga is a parameter of the total gain Go as expressed by the equation (1), when the
value of the gain Ga fluctuates, the optimum value of the gain β of the feedback circuit 30 also
fluctuates.
[0030]
Therefore, in the present embodiment, the gain adjustment circuit 34 is provided in the feedback
circuit 30, and the gain adjustment circuit 34 is controlled by the gain control unit 50 to adjust
the gain β.
The gain adjustment circuit 34 includes, for example, a plurality of resistors switchable by a
switch, and the gain control unit 50 can adjust the gain β by selecting the resistor
corresponding to the desired gain β by the switch.
Alternatively, the gain adjustment circuit 34 may include a variable resistor, and the gain control
unit 50 may adjust the gain β by setting the resistance value of the variable resistor to a
resistance value corresponding to a desired gain β.
[0031]
Further, in FIG. 2, the input operation unit 60 receives an input of information such as a gain Ga
or a model number as identification information of a power amplifier connected to the system
100 from the user, and notifies the gain control unit 50 of the input identification information.
Do. The user may input, for example, the gain Ga or the model number indicated in the
specification of the power amplifier or the like.
[0032]
The gain control unit 50 includes an arithmetic unit 52 and a memory 54. In the memory 54, an
optimum gain value is registered in advance as a gain index value for each power amplifier in
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association with identification information such as the gain Ga of the power amplifier and the
model number. Arithmetic unit 52 acquires identification information of the power amplifier
incorporated in system 100 via input operation unit 60, reads out a gain value corresponding to
the acquired identification information from memory 54, and corresponds to the read gain value.
, And controls the gain adjustment circuit 34 to set the gain β of the feedback circuit 30.
[0033]
As described above, in the present embodiment, in the MFB speaker system 100 in which any
power amplifier can be used, the memory 54 is previously associated with the identification
information of the power amplifier, and the gain β of the feedback circuit 30 is used as a gain
index value. It is registered. Therefore, the user can easily set the optimum gain β by inputting
predetermined identification information such as the gain Ga and the model number of the power
amplifier connected to the system 100. Therefore, according to the MFB speaker system 100
according to the present embodiment, an arbitrary power amplifier can be used, and the total
gain Go can be easily adjusted to an appropriate value.
[0034]
Subsequently, a first modification will be described using the drawings. In the above
embodiment, the gain β is registered in advance in the memory 54 in association with the
identification information of the power amplifier, and when the user inputs the identification
information of the power amplifier to be connected, the gain β is automatically set. An example
has been described. On the other hand, in the first modified example, an example will be
described in which the gain β is set by user operation based on the gain index value provided
from the system 100 side.
[0035]
FIG. 3 shows a configuration of an MFB speaker system 100 according to a first modification.
The first modification differs from the embodiment in that an adjustment operation unit 62 and a
display unit 64 are added. The display section 64 displays the gain Ga of the power amplifier 10
and the overall gain Go as a gain index value, and the user can gain so that the overall gain Go
matches the gain Ga via the adjustment operation section 62. Adjust β. The gain may be
displayed as it is, or may be displayed as a bar whose length changes according to the gain value.
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[0036]
Here, the gain Ga can be directly input by the user via the input operation unit 60 and can be
displayed on the display unit 64. Alternatively, gain Ga is registered as a gain index value in
advance in memory 54 in association with identification information such as the model number
of the power amplifier, and identification information such as the model number of the power
amplifier to be connected is input by the user. The gain Ga corresponding to the input
identification information 50 may be read from the memory 54 and displayed on the display unit
64. Further, the total gain Go may be calculated by the calculation unit 52 based on the equation
(1) and displayed on the display unit 64.
[0037]
As described above, in the first modification, while the user compares the gain Ga, which is the
gain index value displayed on the display unit 64, with the overall gain Go, the gains Ga and the
overall gain Go substantially match. Adjust β. According to the first modification, since the target
gain is displayed on the display unit 64, adjustment of the gain β is facilitated.
[0038]
If the gain Ga can be specified, it is possible to calculate the gain β at which the gain Ga and the
general gain Go coincide with each other by calculation based on the equation (1). That is, in
order to make the total gain Go and the gain Ga coincide, it suffices to obtain β satisfying the
following equation (2): Ga = GaGh / (1 + Ga · Gs · Gh · β) (2)
[0039]
The calculation unit 52 may obtain β based on the following expression (3) obtained by
obtaining expression (2) for β. β = (Gh-1) / GhGaGs (3)
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[0040]
In the above, it is necessary to input the identification information of the power amplifier by the
user, but this input operation can be omitted. That is, if it is possible to detect the output signal
level of the power amplifier when the feedback circuit is in the inactive state, the gain index value
can be set according to the relationship with the input signal. This case will be described as
second to fourth modified examples.
[0041]
First, a second modification will be described below using the drawings.
[0042]
FIG. 4 shows a configuration of an MFB speaker system 100 according to a second modification.
In the second modification, a switch 36 for turning on / off the feedback function of the feedback
circuit 30, a gain switching circuit 34 for switching the gain of the auxiliary amplifier 32, and an
output detector 70 for detecting the output voltage of the power amplifier 10 are provided. This
is different from the above embodiment.
[0043]
In the second modification, first, the feedback circuit 30 is turned off by opening the switch 36,
and the gain of the auxiliary amplifier 32 is set to 1. In this state, the input signal So not
subjected to the feedback action is input to the power amplifier 10, and the output voltage Vo of
the output signal output from the power amplifier 10 is detected according to the input signal So.
In the second modification, this output voltage Vo is set as a gain index value. Next, the feedback
circuit 30 is turned on, and the gain of the auxiliary amplifier 32 is set to Gh. In that state, the
input signal So subjected to the feedback action is input to the power amplifier 10, and the
output voltage Vt of the output signal output from the power amplifier 10 is detected according
to the input signal So, and the output voltage Vt is a gain The gain β is adjusted to coincide with
the output voltage Vo which is an index value.
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[0044]
Here, the output voltage of the power amplifier 10 has a correlation with the overall gain Go of
the system 100. On the other hand, the output voltage Vo of the power amplifier 10 according to
the input signal So which is not subjected to the feedback action (when the switch 36 is open and
the gain of the auxiliary amplifier 32 is 1) is the original gain of the power amplifier 10 It has a
correlation with Ga. Therefore, when an input signal higher than the lowest resonance frequency
(low band limit frequency) on the sound pressure frequency characteristic of the speaker 20 is
input, the feedback operation is received (the switch 36 is closed and the gain of the auxiliary
amplifier 32 is When the output voltage Vt from the power amplifier 10 according to the input
signal So matches the output voltage Vo having a correlation with the gain Ga, it is equivalent to
the overall gain Go matching the gain Ga of the amplifier Do. That is, in the case where the input
signal So is in a feedbackable frequency band and at least the lowest resonance frequency of the
speaker 20, the gain β of the feedback circuit 30 is set so that the output voltage Vt matches the
output voltage Vo. The total gain Go can be adjusted to an ideal value in the MFB speaker system.
[0045]
As described above, according to the second modification, the system 100 adjusts the gain β of
the feedback circuit 30 such that the total gain Go matches the gain Ga even if the user does not
input the identification information of the power amplifier 30. Therefore, the feedback amount
suitable for the power amplifier connected by the user can be easily set.
[0046]
As described above, the input signal So needs to be a frequency signal within a frequency band to
which the feedback circuit 30 can feedback, and a frequency signal higher than the lowest
resonance frequency. Therefore, for example, the input signal So may be input by reproducing a
so-called test CD in which a predetermined frequency signal fi satisfying the above conditions is
recorded. Alternatively, a signal generation unit that outputs a predetermined frequency signal fi
may be provided in the system 100 and input from the signal generation unit.
[0047]
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In the second modification, the gain control unit 50 adjusts the gain β so that the output voltage
Vt of the power amplifier 10 when the feedback circuit 30 is on matches the output voltage Vo
when the feedback circuit 30 is off. An example was described. However, for example, as in the
first modification, the adjustment operation unit 62 and the display unit 64 are provided in the
system 100, and the output voltage Vo as the gain index value and the output voltage Vt are
displayed on the display unit 64, By operating the adjustment operation unit 62, the user may
adjust the gain β so that the output voltage Vt matches the output voltage Vo.
[0048]
Furthermore, without displaying the output voltage Vo or the output voltage Vt on the display
unit 64, the user operates the adjustment operation unit 62 while adjusting the gain β by the
user's manual operation while letting the user listen to the output sound of the speaker 20. It is
also good. That is, first, with the feedback circuit 30 turned off, the voice of the speaker 20 is
input to the user when the input signal So of a signal within the feedbackable frequency band
and above the lowest resonance frequency of the speaker 20 is input. to make listen. Next, the
feedback circuit 30 is turned on, and the user hears the sound of the speaker 20 when the input
signal So is input. The user adjusts the gain β through the adjustment operation unit 62 so that
the sound of the speaker 20 when the feedback circuit 30 is on matches the sound of the speaker
20 when the feedback circuit 30 is off. That is, in this case, the output sound of the speaker 20
when the feedback circuit 30 is in the off state corresponds to the gain index value. Further, for
example, an audio sensor for detecting the output audio level of the speaker 20 is separately
provided in the system 100 without relying on the user's hearing, and the audio sensor detects
the output audio of the speaker 20 when the feedback circuit 30 is off. Set the output sound level
as a gain index value. Next, the feedback circuit 30 detects the output voice of the speaker 20 in
the on state by the voice sensor, and the gain β is set by the gain control unit 50 or user
operation so that the output voice level matches the gain index value. You may adjust.
[0049]
In addition, in the second modification, an example has been described in which the gain of the
auxiliary amplifier 32 is set to 1 when setting the gain index value, and the gain of the auxiliary
amplifier 32 is switched to Gh when adjusting the gain β of the feedback circuit 30. However,
the present invention is not limited to this. For example, when the switch 36 is open and the gain
of the auxiliary amplifier 32 is set to Gh, the output signal voltage of the power amplifier 30
detected is multiplied by 1 / Gh, and this is set as a gain index value. After that, the switch 36 is
08-05-2019
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set to the closed state, and the gain β of the feedback circuit 30 is set so that the output signal
voltage of the power amplifier 10 detected with the gain of the auxiliary amplifier 32 remaining
at Gh matches the gain index value. You may adjust. In this case, the gain switching circuit 34
can be omitted.
[0050]
Subsequently, a third modification will be described. The configuration of the MFB speaker
system according to the third modification may be the same as that of the second modification,
as shown in FIG.
[0051]
In the second modification, the function of the feedback circuit 30 is turned off to obtain an input
signal not subjected to the feedback action, and the output voltage Vo from the power amplifier
10 corresponding to the input signal is used as a reference. An example of adjusting the gain β
has been described. However, even if the feedback circuit 30 is in the ON state, for example, if it
is an input signal that is higher than the lowest resonance frequency of the speaker 20 and is a
predetermined frequency fi ′ outside the frequency band where the feedback circuit 30 can
feedback. An input signal not subjected to feedback can be obtained. Therefore, the same effect
can be obtained by adjusting the gain β using the output voltage Vo 'at that time as a gain index
value.
[0052]
Therefore, in the third modification, first, the gain control unit 50 sets the feedback circuit 30 in
the on state, and sets the gain of the auxiliary amplifier 32 to a predetermined gain Gh. In this
state, the frequency signal fi ′ satisfying the above conditions is input to the power amplifier 10
through the frequency characteristic correction unit 40 and the auxiliary amplifier 32, and the
output voltage Vo ′ at that time is used as a gain index value in the output detector 70. To
detect. Next, the gain control unit 50 turns on the feedback circuit 30, and with the gain of the
auxiliary amplifier 32 remaining at the predetermined gain Gh setting, it is equal to or higher
than the lowest resonance frequency of the speaker 20, and the feedback circuit 30 can perform
feedback. The frequency signal fi within a certain frequency band is input to the power amplifier
10 via the frequency characteristic correction unit 40 and the auxiliary amplifier 32. Next, the
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output voltage Vt at that time is detected by the output detector 70, and the gain β is adjusted
so that the detected output voltage Vt matches the output voltage Vo '. Thereby, similarly, the
gain Ga and the overall gain Go can be made to substantially coincide with each other.
[0053]
Subsequently, a fourth modified example will be described below using the drawings.
[0054]
FIG. 5 shows the configuration of an MFB speaker system 100 according to a fourth modification.
The third modification is different from the above-described embodiment and the other
modifications in that a comparator 80 and an input level adjustment unit 86 are provided. The
comparator 80 includes a first comparator 82 and a second comparator 84 that compare the
output voltage with a predetermined reference voltage. The input level adjustment unit 86
adjusts the input signal level (input voltage) of the frequency signal to be input.
[0055]
In the fourth modification, first, the output voltage Vt of the output signal output from the power
amplifier 10 according to the input signal not subjected to the feedback action matches the
predetermined first reference voltage Vk1. Adjust the signal level of the input signal. Thereafter,
the feedback circuit 30 is turned on, and the output voltage Vt 'of the output signal output from
the power amplifier 10 according to the level-adjusted input signal matches the second reference
voltage Vk2 determined in advance. Adjust the gain β.
[0056]
More specifically, first, the feedback circuit 30 is turned off, and the gain of the auxiliary
amplifier 32 is set to a predetermined gain Gh. In this state, a frequency signal fi within a
frequency band which is equal to or higher than the lowest resonance frequency of the speaker
20 and to which the feedback circuit 30 can feedback is input to the power amplifier 10 via the
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frequency characteristic correction unit 40 and the auxiliary amplifier 32. Next, the output
detector 70 detects the output voltage Vj at that time, and the first comparator 82 compares the
output voltage Vj with the first reference voltage Vk1. Furthermore, gain control unit 50 refers to
the comparison result and controls input level adjustment unit 86 to adjust the input signal level
of frequency signal fi such that output voltage Vj matches first reference voltage Vk1. .
[0057]
Next, the feedback circuit 30 is turned on to set the auxiliary amplifier 32 to a predetermined
gain Gh. In this state, the frequency signal fi after level adjustment is input to the power amplifier
10. Next, the output detector 70 detects the output voltage Vj 'at that time, and the second
comparator 84 compares the output voltage Vj' with the second reference voltage Vk2. The gain
control unit 50 refers to the comparison result and controls the gain adjustment circuit 34 to
adjust the gain β such that the output voltage Vj 'matches the second reference voltage Vk2.
[0058]
In the fourth modification, the second reference voltage Vk2 corresponds to the gain index value,
and the second reference voltage Vk2 has a value smaller than the first reference voltage Vk1 by
the gain which is lowered by turning on the feedback circuit 30. . That is, the second reference
voltage Vk2 corresponds to a value obtained by subtracting the gain Gh from the first reference
voltage Vk1.
[0059]
By adjusting the gain β as described above, the gain Ga and the overall gain Go can be made to
substantially coincide with each other.
[0060]
As in the first modification, the adjustment operation unit 62 and the display unit 64 are
provided in the system 100, and the second reference voltage Vk2 and the output voltage Vj 'are
displayed on the display unit 64, and the user adjusts By operating the operation unit 62, the
gain β may be adjusted such that the output voltage Vj ′ matches the second reference voltage
Vk2.
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[0061]
Also, as in the second modification, the frequency signal fj that is equal to or higher than the
lowest resonance frequency of the speaker 20 may be input by reproducing the test CD, or a
signal generator may be separately provided and input. It is also good.
[0062]
Furthermore, each unit constituting the MFB speaker system 100 according to the abovedescribed embodiment and each modification may be configured by hardware or may be
configured by software.
Of course, one part may be configured by hardware, and the other may be configured by
software.
[0063]
In each of the above-described embodiment and each modification, the feedback signal from the
feedback circuit 30 is input to the input side of the auxiliary amplifier 32, but may be input to
the output side of the auxiliary amplifier 32.
[0064]
It is a figure for demonstrating the basic composition of a MFB system speaker system.
It is a functional block diagram showing the composition of the MFB method speaker system
concerning this embodiment.
It is a functional block diagram which shows the structure of the MFB system speaker system
which concerns on a 1st modification.
It is a functional block diagram which shows the structure of the MFB system speaker system
which concerns on a 2nd modification and a 3rd modification. It is a functional block diagram
which shows the structure of the MFB system speaker system which concerns on a 4th
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modification.
Explanation of sign
[0065]
Reference Signs List 10 power amplifier 20 speaker 22 vibration sensor 30 feedback circuit 32
auxiliary amplifier 34 gain adjustment circuit 36 switch 40 frequency characteristic correction
unit 50 gain control unit 60 input operation unit 62 adjustment operation unit 64 display Part,
70 output detector, 80 comparator, 86 input level adjustment part, 100 MFB speaker system.
08-05-2019
19
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