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JPS59185498

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPS59185498
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
improvement of a motional feedback type speaker apparatus equipped with a bridge type speed
detection circuit. [Background of the invention] Conventionally, a bridge type speed detection
circuit is provided as an apparatus for expanding the bass reproduction range of a small speaker
and reducing distortion, and after applying speed feedback to the speaker, the low frequency
band is expanded by the low frequency boost circuit. An apparatus has been proposed. A block
diagram of this device is shown in FIG. The operation of this apparatus will be described below
with reference to the drawing. In FIG. 1, 1 is an input terminal, 2 is a low-pass boost circuit, 3 is a
subtractor, 4 is a power amplifier, 5.6.7 is an impedance element forming a bridge circuit, 8 is a
bass speaker unit, 9 Is a differential amplifier, 10 is a feedback circuit, and 11 is a bridge circuit
input terminal. The input signal from the input terminal 1 is input to the power amplifier 4
through the low-pass boost circuit 2 and the subtractor 3, and the output of the power amplifier
4 is applied to the page input terminal 11 of the ripple circuit. Due to the impedance element
5.6.7 of the adjusted bridge circuit, the differential input Ik of the differential amplifier 9
generates a voltage proportional to the vibration speed of the vibration system (voice coil) of the
bass-peaker unit 8. The voltage is amplified to a desired magnitude by the differential amplifier 9
and input to the feedback circuit 10. The amplitude and phase of the velocity signal are adjusted
by the feedback circuit 10 and input to the subtracter 3 to perform velocity feedback. Assuming
that the sound pressure frequency characteristic of the bass speaker unit 8 before the speed
feedback is 14 in FIG. 2, the sound pressure frequency characteristic changes to 14 by the speed
feedback. The input voltage to the low frequency speaker unit 8 changes from 12 to 12 'by speed
feedback. When the low range boost indicated by 13 is performed by the low range boost circuit,
the input voltage to the bass speaker unit 8 changes to 12 and the sound pressure frequency
characteristic of the speaker changes to 14. As described above, it is possible to expand the bass
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reproduction range while performing the speed feedback to reduce the distortion. However, this
device has the following problems. One is that there is little distortion reduction effect at high
output. This cause will be described with reference to FIGS. 3 to 5. FIG. 3 is a circuit diagram
showing an example of the bridge circuit in FIG. 1. Here, the impedance element 5 is composed
of the coil 17 and the resistor 18, and the impedance elements 6 and 7 are composed of the
resistors 18 and 18, respectively. The bass speaker unit 8 can be regarded equivalently as being
composed of the coil 17, the resistor 18 and the back electromotive force source 16.
The voltage due to the speaker drive co-source 15 is generated between the X point and the Y
point of this special charge bridge circuit, and the equilibrium conditions are good in% equation
(1) (2) in equation (1) (2) where R: resistance 18 Resistance value R 1: resistance value of
resistance 18 ? R 2: resistance value of resistance 18 R 3: resistance value of resistance 18 ? ?
? L: inductance of coil 17 ? However, in the case of the conventional bass loudspeaker unit 8 as
shown in FIG. 4, the resistance R and the inductance L of the loudspeaker change with the input
voltage as shown by the curve 30.31 in FIG. The resistance R increases as the temperature of the
voice coil 24 rises, and the inductance L decreases as the vibration of the voice coil 24 becomes
large and jumps out of the magnetic circuit. As a result, when the output is large, the equilibrium
condition shown in equation (IX2) does not hold (that is, between the point X and the point Y
both of the back electromotive force source 16 and the speaker drive voltage source 15
proportional to the speed signal The voltages overlap, the velocity signal is distorted, and the
distortion reduction effect by the velocity feedback is reduced. In FIG. 4, 19 is a camp, 20 is a
diaphragm, 21 is an edge, 22 is a spider, 23 is a bobbin, 24 is a voice coil, 25 is a center ball, 26
is a top plate, 27 is a permanent magnet, and 28 is Back plate, 29 is a frame. Another problem is
that the low pass boost circuit 2 reduces the effective dynamic range. This will be described with
reference to FIG. In FIG. 6, assuming that the straight line 32 is the power amplifier 4Q saturation
voltage level, the signal level is low as shown by a broken line 33 at a large output when a lowpass boost by AdB is performed as shown by the broken line 34 at a small output. The saturation
voltage level 32 is reached and eventually the dynamic range is reduced by AdB. As described
above, there are problems with the prior art, and the improvement effect is small while the
apparatus becomes complicated. [Object of the invention] An object of the present invention is a
motional feedback type which is excellent in distortion reduction effect at high output and is
suitable for expansion of a bass reproduction range without eliminating the drawbacks of the
prior art described above and reducing the dynamic range. To provide a speaker device of
[Summary of the Invention] In order to achieve the above object, the speaker device according to
the present invention has a speaker structure in which changes in the inductance and resistance
of the speaker become small so that the balance condition of the bridge circuit is satisfied even at
high output. In the case of a large signal, it adopts an automatic variable acid boost circuit that
smoothly reduces the low range boost amount.
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Embodiments of the present invention will be described below with reference to the drawings.
FIG. 7 is a block diagram showing a speaker apparatus according to an embodiment of the
present invention, and the speaker apparatus shown in FIG. 7 has a low pass boost circuit 2
compared to that shown in FIG. In the automatic variable low pass boost circuit 2 ', the bass
speaker unit is changed from eight to eight. The bass speaker unit 8 has the structure shown in
FIG. 8, and the center ball 25 is longer than the upper end surface of the voice coil 24 by the
length H. H should be approximately equal to the maximum amplitude expected at the maximum
output sound pressure level. Therefore, the inductance of the voice coil 24 hardly changes
because it is always in the center ball 25 or the voice coil 24 even when the amplitude is large at
the time of high output. In addition, heat is easily dissipated from the voice coil to the center ball,
and the temperature rise of the voice coil is reduced. As a result, the changes in the resistance R
and the inductance L of the bass speaker unit 8 are as shown in FIGS. 30 and 31. The balance
condition of the bridge circuit is almost satisfied even at the time of large output. Therefore, an
accurate velocity signal can be obtained even at a large output, and the distortion reduction
effect by velocity feedback can be sufficiently exhibited. FIG. 9 is a characteristic diagram
showing the operating characteristics of the automatic variable low-pass boost circuit 2. As
shown by the broken line 33 at high output, 115 indicates the low-pass boost of AdB indicated
by the broken line 34 at low output. Reduce to prevent the low pass level from reaching the
saturation voltage level 32 of the power amplifier. FIG. 10 shows input / output characteristics in
the low band of the power amplifier when the conventional low band boost circuit 2 and the
automatic variable low band boost circuit 2 are added. Assuming that the straight line 35 is the
input / output characteristic of the power amplifier alone, when performing the AdB low-pass
boost with the conventional low-pass boost circuit 2, the input / output characteristic becomes
the dotted line 36, and the dynamic range decreases. In the case of the automatic variable lowpass boost circuit 2, at low output, low-pass boost is performed as usual with AdB, but at high
output, the boost ? amount is reduced smoothly as indicated by the alternate long and short
dash line 37. The same dynamic range as in the case is secured. FIG. 11 is an automatic variable
low pass boost circuit 2 f. In the lock diagram, 1 is an input terminal, 38 is an automatic variable
low pass boost circuit output terminal, 39 is an adder, 40 is a control voltage generation circuit,
41 is a voltage control amplifier, and 42 is a low pass filter. The signal from the input terminal 1
is divided into two paths, one of which is directly input to the adder 39, and the other is input to
the filter filter 42.
The output of the filter 42 is divided into two paths, one of which is input to the voltage control
amplifier 41 and the other of which is input to the control voltage generation circuit 40. The
control voltage generation circuit 40 first converts the output of the low / (filter 42 into a DC
signal indicating an absolute value, and then compares it with a reference voltage. If the signal
DC voltage is larger than the reference voltage, When the voltage is smaller than the signal DC
voltage, the reference voltage is output to the voltage control amplifier 41 as a control signal. In
the voltage control amplifier 41, the control signal changes the amplification degree of the
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output from the low pass filter 42 to change the low range boost amount. By providing the
reference voltage, a constant low-pass boost can be performed at the time of a small signal. FIG.
12 shows the relationship between the harmonic distortion level in the low band and the input
voltage. In the case of the conventional speaker device, the second harmonic distortion is shown
by the solid line 44, and the third harmonic distortion is shown by the broken line 43. The
second harmonic distortion is shown by a dotted line 44 ', and the third harmonic distortion is
shown by an alternate long and short dash line 43, so that the distortion at the time of large
output is greatly reduced. As described above, according to the present invention, in the motional
feedback type speaker apparatus equipped with the bridge type speed detection circuit, the
equilibrium condition of the bridge circuit is almost satisfied even at the large output, so the
large output There is an effect that the distortion reduction effect at the time of In addition, the
dynamic range does not decrease because of the automatic variable low range boost circuit in
which the low range boost amount decreases smoothly at high output.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing an example of a conventional motioner / I / 11 feedback type
speaker device, and FIG. 2 is a characteristic diagram showing frequency characteristics for
explaining the operation principle of FIG. Fig. 4 is a circuit diagram showing an example of a
bridge circuit, Fig. 4 is a cross-sectional view showing a structure of a bass loudspeaker unit used
in the conventional example of Fig. 1, and Fig. 5 is used for the conventional example and the
present invention. Figure 6 is a characteristic diagram showing the characteristics of the low-pass
boost circuit used in the conventional example, and FIG. FIG. 8 is a cross-sectional view showing
the structure of a speaker used in the present invention, and FIG. 9 is a characteristic diagram for
explaining the characteristics of an automatic variable low-pass boost circuit used in the present
invention. , Figure 10 is a conventional low A characteristic diagram for explaining the difference
in operation between the boost circuit and the automatic variable low-pass boost circuit of the
present invention, FIG. 11 is a block diagram of the automatic variable boost circuit, and FIG. 12
is lower harmonic distortion level vs. input voltage FIG. 8 is a characteristic diagram showing the
change of V in the case of the conventional example and the case of the present invention in
comparison.
Signs 1 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и -и и Impedance
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elements, 8, 8 и и и и и и и и и Loudspeaker unit и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и bridge circuit Input terminals 12, 12, 12 Speaker driving voltage
characteristics 13, Boost circuit characteristics 14.14, 14 Speaker sound pressure characteristics
15,. ииииииииии Speaker drive voltage source, 16 ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии Coil, 18, 18, 18.
ииииииииииии Resistance, 19 иии ....... Bobbin 24... Voice coil 25 25, 25... Center ball 26 26 Top plate 27
Permanent magnet 28. и и и и и и и и Back plate, 29 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и Automatic
variable low-pass boost circuit и и и и и и и и и и и и и и и и и и и и и I / O characteristics of the power amplifier,
38 и и и и и и и и и Automatic variable low-pass frequency и и и и и и и и и и и и и и и и и и и и Adder, 40 и и и и и
Control voltage generation circuit, 41 и и и и и и Voltage control amplifier, 42 и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и Attorney Attorney Namiki
Akio 1st vA Figure 11 Figure 4 Figure 5 Figure 7 Figure 8 Figure 9 (Perio 51 51 10 ? ? ? ? N
N U U U 12 ? ? ? ?
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