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JPH077787

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DESCRIPTION JPH077787
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electronically controlled speaker system which eliminates harmonic distortion components
generated during speaker reproduction and reproduces high-quality sound even during highpower reproduction. Is generated through a non-linear circuit to generate a harmonic
component, to be an antiphase signal at the same level as the harmonic distortion generated in
the speaker, to be added to the electrical input signal and added to the speaker.
[0002]
2. Description of the Related Art A loudspeaker generates harmonic distortion due to poor
linearity of a support system such as an edge or a damper or a drive system such as a magnetic
circuit. Here, the horn speaker will be particularly described.
[0003]
Horn speakers are widely used because they have a high efficiency of electricity and sound
conversion and can reproduce the sound pressure of a large output even with a small input
voltage. FIG. 3 shows a horn speaker system. An electric signal from the electric input unit 1 such
as music and voice is amplified by the power amplifier 2 and then connected to and driven by the
horn speaker 3. Fig. 4 shows sound pressure frequency characteristics and harmonic distortion
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1
frequency characteristics at a point on the axis 1 m away from the horn speaker 3 by adding a
sine wave voltage of 1.2 V to the actual horn speaker 3, where A is the reproduction sound
pressure, B indicates second harmonic distortion and C indicates third harmonic distortion. It can
be seen that high efficiency sound pressure is reproduced even by adding a small input voltage,
but a large amount of second harmonic distortion components are also generated. FIG. 5 shows
the on-axis frequency characteristics and harmonic distortion components when an input voltage
of 2 V is applied to the horn speaker 3 measured in FIG. Here, A, B and C indicate the same as in
the case of FIG. The output sound pressure level is about 3.5 dB higher than in the case of FIG. 4,
and the second harmonic distortion component is about 7 dB higher.
[0004]
However, although a horn speaker can reproduce high-power sound with a small input voltage, a
high level second harmonic distortion component is generated and the level is generated. Also,
there is a problem that the larger the output level, the larger the proportion of the distortion
level. A large amount of distortion of the horn speaker occurs because a large sound pressure is
generated in the horn driver and a phase equalizer inside the horn driver to generate air
distortion, and the second harmonic distortion component is mainly.
[0005]
An object of the present invention is, in view of the above problems, to enable low-distortion,
high-quality sound reproduction even when reproducing a high output sound pressure level.
[0006]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
relates to the reverse phase of the harmonic distortion generated when an electrical input signal
such as music or voice is reproduced by a speaker. A non-linear circuit for generating a
component, and a means for automatically adjusting the amount of distortion generated in the
linear circuit by an input voltage applied to the speaker, wherein the output of the non-linear
circuit is amplified and added to the speaker It is.
[0007]
The invention according to claim 2 is characterized in that the non-linear circuit means generates
an anti-phase signal of harmonic distortion generated when an electrical signal such as music or
voice is reproduced by a speaker, and the non-linearity by the input voltage applied to the
speaker A means for automatically adjusting the amount of distortion generated in the circuit; a
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means for subtracting the input signal from the output of the non-linear circuit to extract only
the distortion component; and a means for correcting the gain or phase with respect to the
distortion component. A means for adding the corrected distortion component and the electrical
input signal is provided, and the output of the adder is amplified and added to the speaker.
[0008]
Furthermore, in the invention according to claim 3, in addition to the invention according to
claim 2, the time required to generate distortion in the non-linear circuit and the time required to
correct the gain and phase with respect to the distortion component are corrected. For this
purpose, two delay devices are provided on the electrical input signal line.
[0009]
According to the present invention, the signal applied to the speaker is distorted according to the
input level to generate a harmonic distortion component, and the distortion component
generated by the speaker itself is adjusted to have the same amplitude and the opposite phase.
This signal is added to an electrical input signal and amplified, and input to a speaker, thereby
canceling distortion generated in the speaker and enabling high-quality, high-output sound
pressure reproduction without occurrence of harmonic distortion.
[0010]
EXAMPLE 1 Hereinafter, a first example of the present invention will be described with reference
to FIG.
In FIG. 1, program signals such as music and voice are input from the electric input unit 1, and
generate a reverse phase component of second harmonic distortion generated in the horn
speaker 3 through the non-linear circuit 4.
The amount of the second harmonic distortion is controlled by the output level of the power
amplifier 2. As the output increases, the amount of the second harmonic distortion component
generated increases, and as the output decreases, the amount decreases. The control signal is
controlled through the control line 5 as described above.
The electrical signal that has passed through the non-linear circuit 4 is a combination of signals
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of reverse phase components of distortion generated in the horn speaker 3, and this electrical
signal is input to the power amplifier 2 and amplified, and then applied to the horn speaker 3.
The sound reproduced from the horn speaker 3 is expressed by the following equation.
[0011]
P = H · E (1) where P is the sound pressure level reproduced by the horn speaker 3, H is the
transmission characteristic of the horn speaker, and E is the electrical input signal.
[0012]
However, since the horn speaker 3 generates the second harmonic distortion as shown in FIGS. 7
and 8, the transfer characteristic H is divided into the distortion-free component Hs and the
distortion component Hn as shown by the following equation.
[0013]
H = Hs + Hn (2) The second harmonic distortion is generated by the distortion generation circuit,
and the electric signal E at this time can be expressed by E = Es-En (3).
Here, the negative sign is attached to the distortion component in order to show that it has an
anti-phase relationship with the distortion generated in the horn speaker 3.
[0014]
Therefore, when equations 2 and 3 are substituted into equation 1, P = (Hs + Hn) (Es-En) = HsEsHsEn + HnEs-HnEn ... (4) Here, distortion is generated in horn speaker 3 in the circuit Since the
distortion component is generated so as to cancel the second harmonic component, in equation
4, −HsEn + HnEs = 0 (5).
Therefore, equation 4 is expressed as the following equation.
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[0015]
P = HsEs−HnEn (6) Here, Hn · En is the product of the distortion component generated by the
horn speaker 3 and the distortion component generated by the non-linear circuit, and since it is a
very weak sound, it is ignored it can.
This is because, for example, a distortion component of 3% is generated in the horn speaker. At
this time, the amount of distortion En generated in the non-linear circuit is also 3%, and Hn · En is
0.03 × 0.03 = 0.0009, which is 0.09%.
[0016]
(Embodiment 2) FIG. 2 shows a second embodiment of the present invention. An electrical signal
is input to the electrical signal unit 1 such as music and voice, and then branched into two. One is
input to the delay circuit 6 having a delay time of τ 1, and the other is input to the non-linear
circuit 4. The non-linear circuit 4 produces an antiphase component that cancels the second
harmonic distortion component generated by the horn speaker 3 according to the output level of
the power amplifier 2. That is, the amount of distortion generated in the non-linear circuit 4 is
controlled by a control signal passing through the control line 5 connecting the output of the
power amplifier 2 and the non-linear circuit 4. The delay time τ 1 of the delay circuit 6 is set to
be equal to the time required to generate a distortion component in the non-linear circuit 4. From
the signal that has passed through the non-linear circuit 4, the electric signal component input in
the electric signal unit 1 is subtracted by a subtractor 9 to separate only the distortion
component. The signal of only the distortion component is input to the transfer function
correction circuit 8 and corrected so as to match the frequency characteristic of the distortion
amount generated by the horn speaker 3. The delay circuit 7 corresponds to the time required
for correction by the transfer function correction circuit 8. The output of the correction circuit 8
is added to the original signal output from the delay circuit 7 through the adder 10, amplified by
the power amplifier 2, and applied to the horn speaker 3. As a result, as shown by equation 5, a
high-power sound without distortion is reproduced from the horn speaker 3.
[0017]
As mentioned above, although it paid attention to the horn speaker 3, even if it attaches to a
normal speaker, this system can be used by the same means, and can eliminate the distortion
component which generate | occur | produces in a speaker system.
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[0018]
As described above, according to the present invention, the harmonic distortion component in
antiphase with the harmonic distortion generated in the speaker is included in the signal for
driving the speaker to drive the speaker itself. The generated harmonic distortion components
cancel each other out, and it is possible to achieve high-quality sound reproduction without
distortion even at the time of high-output sound pressure reproduction.
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