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JPH0799698

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DESCRIPTION JPH0799698
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker system having a feedback circuit for improving bass reproduction capability.
[0002]
2. Description of the Related Art In recent years, with the recent digitization of audio output
equipment, the speaker system is desired to expand the reproduction band of high sound quality,
high output, and low tone range, and a speaker system having a feedback circuit is often used
conventionally. It was being done.
[0003]
Below, the Kelton type speaker system provided with the conventional feedback circuit is
demonstrated using FIG.
[0004]
As shown in FIG. 10, a Kelton cabinet 2 having a port 7 (the inside of the cabinet is divided into a
cavity 2a and a cavity 2b by a cavity division member 2c, and the speaker unit 1 is attached to
the cavity division member 2c. The voltage proportional to the vibration system speed of the
speaker unit 1 attached to the passive radiator or the cabinet attached with the port 7 at the
opening portion is detected by the bridge circuit 4 having one side of the speaker unit 1 and the
detected voltage is transformed The feedback circuit 5 negatively feedbacks to the power
amplifier 3 for driving the speaker unit 1 as it is or through the differentiation circuit.
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[0005]
However, in the above-described conventional configuration, when the voltage detected by the
bridge circuit 4 is transformed and fed back as it is or through a differentiating circuit, the
electrical impedance of the speaker unit is the voice of the speaker unit. Due to the coil
inductance, it has a curve that gradually rises from the middle to high range (around 400 Hz),
and affects the voltage rise and phase rotation detected by the bridge circuit.
At this time, especially when the voice coil inductance of the speaker unit 1 is large, it is not
possible to control the rise of the middle to high frequency range of the electric impedance, and
the detected voltage detected by the bridge circuit 4 is fed back to the power amplifier. There is a
problem that the positive feedback causes the power amplifier to oscillate and it becomes
impossible to apply feedback using a bridge circuit over a wide band.
[0006]
The present invention solves the above-mentioned conventional problems, and has a first object
to provide a speaker system capable of feedback using a bridge circuit over a wide band.
[0007]
A second object is to provide a speaker system capable of feedback using a bridge circuit over a
wide band by using a plurality of speaker units having different reproduction bands.
[0008]
The third object is to provide a speaker system capable of performing feedback using a bridge
circuit over a wide band by setting the bass reproduction limit frequency lower than in the case
of using a closed cabinet.
[0009]
The fourth object is a speaker system capable of feedback using a bridge circuit over a wide band
by using a plurality of speaker units having lower bass reproduction limit frequencies than in the
case of using a closed cabinet and using different speaker bands. To provide.
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[0010]
A fifth object is to provide a speaker system capable of feedback using a bridge circuit which
does not require a low pass filter for bass reproduction.
[0011]
It is a sixth object of the present invention to provide a speaker system capable of performing
feedback using a bridge circuit over a wide band by combining a speaker unit having a
reproduction band higher than that for bass reproduction.
[0012]
[Means for Solving the Problems] In order to achieve the above first object, the speaker system of
the present invention is a bridge circuit in which the cabinet is sealed except for the sound
pressure radiation part and the speaker unit is one side. A voice coil impedance correction circuit
consisting of a resistor and a capacitor is disposed in parallel to the speaker unit, and after
transforming the detection voltage of the bridge circuit, a feedback circuit that feeds back to the
power amplifier driving the speaker unit as it is or through a differentiation circuit. It has the
provided configuration (first configuration).
[0013]
Further, in order to achieve the above second object, in addition to the configuration of the first
speaker system, the speaker system of the present invention has a configuration in which a
speaker unit having different reproduction bands is connected in parallel to the speaker unit
(second Configuration).
[0014]
In addition to the configuration of the first speaker system, the speaker system of the present
invention has a configuration (third configuration) in which a passive radiator or a port is
attached to a cabinet in order to achieve the third object. There is.
[0015]
In addition to the configuration of the first speaker system, the speaker system of the present
invention has a passive radiator or port attached to a cabinet and a different reproduction band
parallel to the speaker unit to achieve the fourth object. It is the structure which connected the
speaker unit which it has (4th structure).
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[0016]
Further, in order to achieve the fifth object, the speaker system of the present invention is the
same as the first speaker system except for the cabinet, but the cavity 1 and the cavity 2 are
formed by the cavity division member in the cabinet. The speaker unit is attached to the cavity
division member, and a Kelton-type cabinet having a passive radiator or a port attached to the
opening of the cabinet is used (fifth configuration).
[0017]
Furthermore, in order to achieve the sixth object, the speaker system of the present invention is
the same as the first speaker system except for the cabinet and the speaker unit, but the inside of
the cabinet is The speaker unit is divided into the cavity 2 and the speaker unit is attached to the
cavity division member, and a passive radiator or a port is attached to the opening of the cabinet
using a Kelton-type cabinet, and different reproduction bands parallel to the speaker unit It is the
composition (the 6th composition) which connected the speaker unit which it has.
[0018]
In the first configuration, the gradual increase of the electrical impedance from the middle to
high range (about 400 Hz) is paralleled to the speaker unit by the voice coil inductance of the
speaker unit of the bridge circuit having the speaker unit as one side. The capacitor is flattened
by the resistors and capacitors placed in the circuit, and the rise and phase rotation of the
voltage detected by the bridge circuit are suppressed over a wide band.
As a result, a voltage proportional to the vibration system speed of the speaker unit can be
detected in the speaker unit to apply a velocity type feedback and an acceleration type feedback
through the differentiation circuit.
At this time, the velocity type feedback acts in a direction to make the vibration system velocity
of the speaker unit constant, and functions as a strengthening of the magnetic circuit of the
speaker unit.
In addition, the acceleration type feedback acts in the direction to make the vibration system
acceleration of the speaker unit constant, and works equivalent to the weight of the vibration
system mass of the speaker unit being made heavier.
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Therefore, by applying the above-mentioned velocity type feedback and acceleration type
feedback in combination, a flat sound pressure frequency characteristic can be obtained over a
wide band and ultra low frequency band.
[0019]
Further, in the second configuration, the reproduction band can be expanded by using a plurality
of speaker units having different reproduction bands.
[0020]
In the third configuration, part of the sound radiated from the back of the speaker unit is
radiated through the passive radiator or port together with the sound radiated from the front of
the speaker unit to enhance the bass reproduction sound pressure. Do.
[0021]
In the fourth configuration, part of the sound radiated from the back of the speaker unit is
radiated through the passive radiator or port together with the sound radiated from the front of
the speaker unit to enhance the bass reproduction sound pressure. In addition to the above, the
reproduction band can be expanded by using a plurality of speaker units having different
reproduction bands.
[0022]
In the fifth configuration, the sound radiated from the speaker unit propagates inside the cavity 1
and is radiated from the passive radiator or port which is the opening.
At this time, the resonance of the in-cavity air compliance component of the cavity 1 and the
cavity 2 and the vibration system mass component of the speaker unit and the passive radiator
or port causes a band pass type acoustic filter of about 12 dB / oct to be applied.
[0023]
Furthermore, in the sixth configuration, the sound radiated from the speaker unit propagates
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inside the cavity 1 and is radiated from the passive radiator or port which is the opening.
At this time, in addition to the fact that the band-pass type acoustic filter of about 12 dB / oct is
applied by the resonance of the cavity 1 and cavity 2 air compliance components in the cavity
and the vibration system mass components of the speaker unit and passive radiator or port. The
reproduction band can be expanded by using a plurality of speaker units having different
reproduction bands.
[0024]
An embodiment of the present invention will be described below with reference to the drawings.
[0025]
FIG. 1 shows a first embodiment of the present invention.
A speaker unit 11 has an effective vibration radius of 65 mm, an effective vibration mass of 12.5
g, a direct current resistance of 5.1 Ω, and an aperture 17 cm having a minimum resonance
frequency of 40 Hz.
The speaker unit 11 is attached to a cabinet 12 which is sealed except for the portion to which
the speaker unit 11 is attached, and the inner volume is 13.8 liters.
In addition, the speaker unit 11 is driven by the power amplifier 13. During this time, R1 = 56
K.OMEGA., R2 = 1.6 K.OMEGA., R3 = 0.1.OMEGA. An impedance correction circuit 17 in which Rs
= 27 Ω and Cs = 27 μF are inserted.
16 is a signal source.
[0026]
The detected voltage from the bridge circuit 14 is in direct proportion to the speed of the
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vibration system of the speaker unit 11, and the feedback circuit 15 combines the voltage
obtained by transforming the detected voltage as it is with the voltage transformed through a
one-time differentiation circuit. It is fed back to the power amplifier 13.
At this time, a voltage proportional to the vibration system acceleration can be obtained by
passing the differentiation circuit once.
Further, the impedance correction circuit 17 arranged in parallel to the speaker unit 11 flattens
the gradual rise of the electrical impedance from the middle to high range (around 400 Hz) due
to the voice coil inductance of the speaker unit 11 and is detected by the bridge circuit 14
Suppress voltage rise and phase rotation.
As a result, when the detected voltage is fed back to the power amplifier 13 from the feedback
circuit 15, the detected voltage becomes positive feedback to prevent the power amplifier 13
from oscillating.
[0027]
In the speaker system configured as described above, MFB (motional feedback) is applied to the
speaker unit 11, and the electromagnetic braking resistance (= (magnetic flux density x effective
conductor length) 2 / DC resistance) of the speaker unit 11 and the effective vibration mass Can
be equivalently made very large and can lower the bass reproduction limit frequency.
FIG. 2 shows sound pressure frequency characteristics of the speaker system having the above
configuration.
a is the characteristic before applying feedback, b is the characteristic after applying feedback, c
is the sound pressure of 200 Hz or more of b, raised according to the sound pressure of 200 Hz
or more of a, from before the feedback Also, it can be understood that the bass reproduction
band is lowered by 1 oct or more.
[0028]
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Next, a second embodiment of the present invention will be described with reference to FIG.
Except for the cabinet 22 and the speaker units 28a and 28b, the second embodiment is the
same as the first embodiment.
The cabinet 22 has a three-way structure in which two speaker units 28a and 28b having a
reproduction band different from the speaker unit 21 in addition to the speaker unit 21 are
attached, and the speaker unit 28b is connected in parallel to the speaker unit 21 via a capacitor
C. It is connected.
The capacitor C is a filter for high pass of the speaker unit 28 b and determines the cross
frequency with the reproduction band of the speaker unit 21.
[0029]
Next, a third embodiment of the present invention will be described with reference to FIG. Except
for the cabinet 32, it is the same as the first embodiment. The cabinet 32 includes a passive
radiator 38 in addition to the speaker unit 31. The passive radiator 38 amplifies part of the
sound radiated from the back of the speaker unit 31 through the passive radiator 38 in phase
with the sound radiated from the front of the speaker unit 31 to enhance the bass reproduction
sound pressure. Do. With this configuration, the reproduction limit frequency can be lowered
compared to the first embodiment. FIG. 5 shows sound pressure frequency characteristics of the
speaker system of this configuration. a is the characteristic before applying feedback, b is the
characteristic after applying feedback, c is the sound pressure of 200 Hz or more of b, raised
according to the sound pressure of 200 Hz or more of a, from before the feedback Also it can be
seen that the bass reproduction band is lowered by nearly 1 oct. The amount of increase in sound
pressure at this time is smaller than that in the first embodiment, and the superiority of the bass
region due to the structure of the cabinet 32 is shown (except for frequencies below 40 Hz). In
the present embodiment, a portion that radiates part of the sound radiated from the back of the
speaker unit 31 is a passive radiator, but this may be a port.
[0030]
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Next, a fourth embodiment of the present invention will be described with reference to FIG.
Except for the cabinet 42, the passive radiator 48 and the speaker units 49a and 49b, the second
embodiment is the same as the first embodiment. The cabinet 42 has a 3-way structure in which
two speaker units 49a and 49b having a reproduction band different from the speaker unit 41 in
addition to the speaker unit 41 are attached, and the speaker unit 49b is connected in parallel to
the speaker unit 41 via the capacitor C. It is connected. The capacitor C is a filter for high pass of
the speaker unit 49 b and determines the cross frequency with the reproduction band of the
speaker unit 41. In the present embodiment, the passive radiator 48 is a portion that radiates a
part of the sound radiated from the rear surface of the speaker unit 41, but this may be a port.
Moreover, although the passive radiator 48 was attached to the back surface of the speaker unit
41 in FIG. 6, it is not limited to the back surface.
[0031]
Next, a fifth embodiment of the present invention will be described with reference to FIG. Except
for the cabinet 52, the second embodiment is the same as the first embodiment. In the cabinet
52, the inside of the cabinet is divided into a cavity 52a and a cavity 52b by a cavity division
member 52c, the speaker unit 51 is attached to the cavity division member 52c, and a passive
radiator 58 is provided at the opening of the cabinet 52. In this configuration, the sound radiated
from the speaker unit 51 propagates inside the cavity 52a, is radiated from the passive radiator
58 which is the opening, and the in-cavity air compliance component of the cavity 52a and the
cavity 52b, the speaker unit 51 and the passive radiator The resonance of 58 vibration system
mass components results in a band-pass acoustic filter of approximately 12 dB / oct. FIG. 8
shows sound pressure frequency characteristics of the speaker system of this configuration. It
can be seen that a is a characteristic before feedback, and b is a characteristic after
feedback, so that the characteristic is flat over 1 oct or more by applying feedback. In the present
embodiment, the portion to which sound is radiated is a passive radiator, but this may be a port.
[0032]
Next, a sixth embodiment of the present invention will be described with reference to FIG. Except
for the cabinet 62, the passive radiator 68, and the speaker units 69a and 69b, the second
embodiment is the same as the first embodiment. The cabinet 62 has a three-way structure in
which two speaker units 69a and 69b having a reproduction band different from the speaker
unit 61 in addition to the speaker unit 61 are attached, and the speaker unit 69b is connected to
the speaker unit 61 in parallel via a capacitor. It is done. This capacitor is a filter for high pass of
the speaker unit 69 b and determines the cross frequency with the reproduction band of the
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speaker unit 61. In the present embodiment, the portion to which sound is radiated is a passive
radiator, but this may be a port.
[0033]
As described above, according to the speaker system of the present invention, the voice coil
impedance correction circuit consisting of the resistor and the capacitor is arranged in parallel to
the speaker unit which is one side of the bridge circuit. It is possible to suppress the rise of the
detection voltage and the phase rotation, and to perform power amplification using a bridge
circuit over a wide band. Further, since a plurality of speaker units having different reproduction
bands are used, the reproduction band can be expanded. In addition, since the speaker unit and
the phase-reversal type cabinet including the passive radiator or port are used, the bass
reproduction sound pressure can be enhanced. Furthermore, since the speaker unit and the
Kelton type cabinet composed of passive radiators or ports are used, band pass acoustic filters
can be applied.
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