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JPH1075494

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH1075494
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound reproducing apparatus having a structure for transmitting sound radiated from a speaker
to a listener by reflecting the sound by means of a sound reflecting plate.
[0002]
2. Description of the Related Art In recent years, a wide directivity characteristic of reproduced
sound is secured by diffusing sound over a wide area by using a reflection plate in a sound
reproducing apparatus, and an expansion of a listening area and improvement of a sense of
reality are achieved. Hereinafter, an example of the above-mentioned conventional sound
reproduction apparatus will be described with reference to the drawings.
[0003]
FIG. 10 shows the structure of a conventional sound reproducing apparatus. In FIG. 10, a conical
acoustic reflector 22 integrally formed on the upper cabinet 25 is disposed on the front surface
of the diaphragm of the speaker 21 fixed upward to the upper cabinet 25 and surrounded by the
loudspeaker 21 and the acoustic reflector 22. The space formed is the front room 23. The top
cabinet 25 is fixed to the bottom cabinet 26, and the top decoration cabinet 27 is fixed to the top
cabinet 25 at the top of the acoustic reflector 22.
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1
[0004]
FIG. 11 is a schematic cross-sectional view showing the structure of the front chamber of the
conventional sound reproducing apparatus, FIG. 12 shows an electro-acoustic equivalent circuit
of the conventional sound reproducing apparatus, and FIG. 13 shows acoustic characteristics of
the conventional sound reproducing apparatus. The sound radiated upward from the speaker 21
at the sound pressure P is reflected by the acoustic reflection plate 22, passes through the front
chamber portion 23, and is emitted widely into space. At this time, under the influence of the
characteristic acoustic impedance Zr of the front chamber portion 23 shown in FIG. 12, as shown
by the solid line in FIG.
[0005]
FIG. 14 shows an electrical correction circuit of a conventional sound reproducing apparatus. In
FIG. 14, the output of the power amplifier 20 is connected to the speaker 21 via the correction
circuit 28. The correction circuit 28 is a trap circuit configured by parallel connection of an
inductor Lt and a capacitor Ct, and the resonance frequency of the trap circuit is set near the
center frequency of the middle mountain peak shown by the solid line in FIG. It cancels and
corrects to a substantially flat characteristic. With regard to the attenuation of the high
frequency band, correction is performed by improving the high frequency band characteristics of
the speaker 1 or the like. By the above correction, acoustic characteristics after correction shown
by the broken line in FIG. 13 are obtained.
[0006]
However, in the conventional sound reproducing apparatus as described above, when the
distance between the sound reflecting plate 22 and the speaker 21 is reduced to achieve a
reduction in thickness, the front room portion 23 becomes narrow, and the acoustic
characteristics are improved. Since the peaks in the middle range become sharper and higher, the
Q of the correction circuit 28 needs to be increased, so it is necessary to lower the DC resistance
component of the inductor Lt and increase the L value or increase the filter order. However, there
is a problem that cost increase and loss of component mounting space occur, making it difficult
to reduce the thickness.
[0007]
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2
The present invention is intended to solve the above-mentioned conventional problems, and an
acoustic reproducing apparatus capable of correcting the influence of the characteristic acoustic
impedance Zr of the front chamber portion 23 in the case of achieving thinning even with a
simple and inexpensive electric circuit configuration. It was made for the purpose of providing.
[0008]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a sound
reproducing apparatus according to the present invention is constructed between an acoustic
reflection plate installed on the front of a speaker for converting an electrical signal into acoustic
energy and the speaker. An acoustic equalizer is configured by providing an opening at the neck
of the Helmholtz resonator facing the front chamber, and matching the resonance frequency
characteristics of the acoustic equalizer with the peak on the acoustic characteristic generated by
the acoustic characteristic impedance of the front chamber. It is configured to lower the upper
mountain.
[0009]
According to the present invention, with the above-described configuration, the acoustic
equalizer reduces the influence of the characteristic acoustic impedance Zr of the front chamber
portion on the acoustic characteristics in achieving thinning, and enables correction of the
acoustic characteristics even with a simple and inexpensive electrical circuit configuration.
Further, the effect can be enhanced by providing a plurality of acoustic equalizers as necessary
and gradually shifting the resonance frequency.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION The invention of the sound reproducing
apparatus according to claim 1 of the present invention is a speaker for converting an electric
signal into sound energy, and a sound which is disposed on the front of the speaker and reflected
from the speaker is reflected and transmitted. And an acoustic equalizer including a Helmholtz
resonator provided with an opening of a neck facing the front chamber, and an acoustic reflector
including the acoustic reflector, the acoustic reflector including the speaker and the acoustic
reflector. The peak on the acoustic characteristic is lowered by matching the peak on the acoustic
characteristic caused by the acoustic characteristic impedance of the section and the resonance
frequency characteristic of the acoustic equalizer, and the influence on the acoustic characteristic
of the characteristic acoustic impedance Zr of the front room section Act to be reduced by the
acoustic equalizer.
[0011]
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The invention of the sound reproduction device according to claim 2 of the present invention is,
in the invention according to claim 1, an acoustic characteristic generated by the acoustic
characteristic impedance of the front chamber by providing a plurality of acoustic equalizers
constituted by Helmholtz resonators. The dispersion setting of the resonance frequency of each
acoustic equalizer in the upper mountain frequency band acts to lower the mountain on the
acoustic characteristic over a wide frequency range.
[0012]
Hereinafter, an embodiment of a sound reproducing apparatus according to the present
invention will be described in detail with reference to FIGS. 1 to 9.
[0013]
(First Embodiment) The structure of a sound reproducing apparatus according to the first
embodiment of the present invention is shown in FIG.
In the figure, a conical acoustic reflection plate 2 whose tip is directed to the diaphragm 1 a is
mounted on the front surface, that is, the upper surface of the diaphragm 1 a of the speaker 1
attached to the upper surface of the upper cabinet 5 to convert electrical signals into acoustic
energy. A space formed integrally with the speaker 1 and the acoustic reflector 2 is a front
chamber 3.
The upper cabinet 5 is integrally fixed to the bottom cabinet 6 to form an acoustic box.
The top decoration cabinet 7 has an opening 7a such as a net or a grill, and is fixed to the upper
part of the acoustic reflector 2 to protect these parts and enhance design.
What differs from the prior art is that the acoustic equalizer 4 is integrally formed with the upper
cabinet 5 and the opening 4 a of the acoustic equalizer 4 is installed facing the front chamber 3.
It is preferable that the upper cabinet 5, the acoustic reflection plate 2, the acoustic equalizer 4
and the like are integrally molded of synthetic resin.
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[0014]
In FIG. 1, the sound radiated from the speaker 1 at the sound pressure P is reflected by the
acoustic reflection plate 2, passes through the front chamber 3, and is emitted to a wide area into
space.
FIG. 2 is a schematic cross-sectional view showing the structure of the front chamber of the
sound reproduction apparatus of the present embodiment, and FIG. 3 is an electro-acoustic
equivalent circuit of the sound reproduction apparatus.
In FIG. 2, a sound pressure P is generated from the speaker 1, and the front chamber portion 3
has a characteristic acoustic impedance Zr. The acoustic equalizer 4 comprises a neck 8 and a
cavity 9, and the neck 4 and the cavity 9 constitute a Helmholtz resonator.
[0015]
Assuming that the acoustic resistance of the neck 8 of the acoustic equalizer 4 is Rh, the acoustic
mass of the neck 8 of the acoustic equalizer 4 is Mh, the acoustic capacitance of the cavity 9 of
the acoustic equalizer 4 is Ch, the resonance frequency is Fh, and Q is Qh in this case The
resonant frequency Fh of
[0016]
Where Q h is
[0017]
It is represented by
FIG. 3 shows an electro-acoustic equivalent circuit of the sound reproduction apparatus
according to the present embodiment, and FIG. 4 similarly shows acoustic characteristics of the
sound reproduction apparatus.
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The sound pressure P radiated from the speaker 1 in FIG. 2 is reflected by the acoustic reflection
plate 2, passes through the front chamber 3 and is radiated to space. At this time, under the
influence of the characteristic acoustic impedance Zr of the front room 3, as shown by the solid
line in FIG. 4A, a high mountain is formed in the middle region and the high region is attenuated.
Here, the resonance frequency Fh of the acoustic equalizer 4 composed of the Helmholtz
resonator is adjusted to the center frequency of the high mountain in the middle range, and the
Qh is made closer to the Q of the mountain to absorb the high mountain in the middle range by
the acoustic equalizer 4 The acoustic characteristic is as shown by the broken line in FIG. Here,
the resonance frequency Fh of the acoustic equalizer 4 and the Qh of its Q are set by adjusting
the shapes of the neck 8 and the cavity 9.
[0018]
FIG. 5 shows a block diagram of the electrical correction circuit in the present embodiment. The
output of the operational amplifier A1, which is an input buffer amplifier, is applied to the
speaker 1 through the resistor R1, the trap circuit Ls, the high frequency correction circuit 11
and the power amplifier 10. The pseudo inductor Ls is composed of resistors R2 and R3, an
operational amplifier A2 and a capacitor C2, and the pseudo inductor Ls constitutes a resonant
circuit composed of a capacitor C1 and a resistor R7, and a trap circuit composed of a
combination with the resistor R1. The high frequency correction circuit 11 is composed of
resistors R4, R5, R6 and a capacitor C2.
[0019]
The resonance frequency of the trap circuit Ls is made to coincide with the high mountain
frequency in the middle range indicated by the solid line in FIG. 4A, and the resistance R7 is set
to Q of the trap circuit so as to make the acoustic characteristics more flat. The high frequency
correction circuit 11 is set to correct the high frequency attenuation characteristics shown by the
solid line in FIG. 4A. FIG. 4B shows the frequency characteristics of the electrical correction
circuit of the sound reproduction device according to the present embodiment configured as
described above. The solid line in FIG. 4C is the acoustic characteristic of the sound reproduction
apparatus before correction, and the broken line is the acoustic characteristic in the case where
the acoustic equalizer 4 and the electrical correction circuit of FIG. 5 are combined.
[0020]
As described above, according to the present embodiment, the height of the mountain in the
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middle region on the acoustic characteristic generated by the characteristic acoustic impedance
Zr of the front chamber 3 is suppressed by the acoustic equalizer 4, and the acoustic circuit 4 is
simple and inexpensive. Characteristic correction can be realized.
[0021]
Second Embodiment FIG. 6 shows the structure of a sound reproducing apparatus according to a
second embodiment of the present invention.
The difference between FIG. 6 and the one in the first embodiment is that the first acoustic
equalizer 12, the second acoustic equalizer 13, and two acoustic equalizers are provided. The
other points are the same as those in the first embodiment of FIG. The same parts as those of the
reproducing apparatus are denoted by the same reference numerals and the description thereof
is omitted. The first and second acoustic equalizers 12 and 13 are integrally formed with the
upper cabinet 5a, and the openings 12a and 13a are disposed facing the front chamber 3. In FIG.
7 which is a cross-sectional view schematically showing the structure of the anteroom portion of
the sound reproduction device of the second embodiment, the first acoustic equalizer 12
constitutes a Helmholtz resonator by the neck portion 14 and the cavity portion 15. The second
acoustic equalizer 13 constitutes a Helmholtz resonator by the neck portion 16 and the cavity
portion 17.
[0022]
FIG. 8 shows an electroacoustic equivalent circuit of the acoustic reproduction device of the
present embodiment. Sound pressure P of the speaker 1, characteristic acoustic impedance Zr of
the front chamber 3, acoustic resistance and acoustic mass of the neck 14 of the first acoustic
equalizer 12 as Rh1 and Mh1, and acoustics of the cavity 15 of the first acoustic equalizer 12.
Let the capacity be Ch1. The acoustic resistance and acoustic mass of the neck portion 16 of the
second acoustic equalizer 13 are Rh2 and Mh2, and the acoustic capacitance of the cavity
portion 17 of the second acoustic equalizer 13 is Ch2.
[0023]
The resonance frequencies Fh1 and Fh2 of the first acoustic equalizer 12 and the second
acoustic equalizer 13, respectively Qh1 and Qh2 of Q are
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[0024]
[0030] is represented.
The solid line in FIG. 9A indicates the acoustic characteristic of this acoustic reproduction device.
The resonance frequencies Fh1 and Fh2 of the first and second acoustic equalizers 12 and 13
composed of Helmholtz resonators are set to be dispersed in the middle mountain frequency
band of the acoustic characteristics, and the middle mountain peaks approach flat By setting Qh1
and Qh2 as described above, the mountain in the middle of the acoustic characteristics is
absorbed, and the acoustic characteristics as shown by the broken line in FIG. 9A are obtained.
Here, the setting of the resonance frequency and Q of each acoustic equalizer adjusts and sets
the shape of each neck and cavity. Further, as in the first embodiment, by performing correction
as shown in FIG. 9B using the electric correction circuit shown in FIG. 5, acoustic characteristics
close to flat as shown by the broken line in FIG. 9C can be obtained. .
[0025]
As described above, according to the present embodiment, a simple and inexpensive electric
circuit can be obtained by suppressing the height of the mountain in the middle region on the
acoustic characteristics generated by the characteristic acoustic impedance Zr of the front
chamber 3 by two acoustic equalizers. Correction of acoustic characteristics can be realized.
[0026]
The use of two acoustic equalizers as in the present embodiment is an effective means in the case
where the middle mountain frequency band on acoustic characteristics is relatively wide, and the
number of acoustic equalizers should be further increased. It is needless to say that it is possible
to flatten the peaks of the middle region on the acoustic characteristics by
[0027]
As described above, according to the sound reproducing apparatus of the present invention, the
opening portion of the neck portion is provided facing the front chamber portion formed
between the sound reflecting plate installed on the front surface of the speaker and the speaker.
The acoustic characteristics are obtained by matching the resonance frequency and Q value of
the acoustic equalizer to the high peaks of the midrange on the acoustic characteristics
generated by the characteristic acoustic impedance Zr of the front chamber portion. A high
mountain in the upper middle range can be absorbed to facilitate correction by the electric
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circuit, and a plurality of acoustic equalizers can be provided and correction over a wide
frequency band can be performed by shifting their resonance frequencies with one another.
Simple and inexpensive electricity Correction of acoustic characteristics in the circuit
configuration can be realized.
[0028]
Brief description of the drawings
[0029]
1 is an exploded perspective view showing the structure of the sound reproduction apparatus
according to the first embodiment of the present invention.
[0030]
Fig. 2 is a schematic cross-sectional view showing the structure of the front chamber as well
[0031]
Fig. 3 also shows an electroacoustic equivalent circuit diagram of the acoustic reproduction
device
[0032]
Fig. 4 same as the acoustic characteristic chart
[0033]
Similarly to FIG. 5, the electric correction circuit diagram in the first embodiment
[0034]
6 is an exploded perspective view showing the structure of the sound reproduction apparatus
according to the second embodiment of the present invention.
[0035]
Fig. 7 is a schematic cross-sectional view showing the structure of the front chamber as well.
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[0036]
Similarly to FIG. 8, an electroacoustic equivalent circuit diagram of the acoustic reproducing
apparatus
[0037]
Fig. 9 is also the acoustic characteristic diagram
[0038]
10 is an exploded perspective view showing the structure of the conventional sound reproducing
apparatus
[0039]
Fig. 11 is a cross-sectional schematic view showing the structure of the front chamber as well
[0040]
The same electroacoustic equivalent circuit as FIG. 12
[0041]
Fig. 13 same as the acoustic characteristic chart
[0042]
Fig. 14 same as the electric correction circuit diagram
[0043]
Explanation of sign
[0044]
Reference Signs List 1 speaker 2 acoustic reflection plate 3 front room 4 acoustic equalizer 5
upper cabinet 6 bottom cabinet 7 decoration cabinet 8 neck 9 of acoustic equalizer 4 cavity part
of acoustic equalizer 4 Zr characteristic cavity of front chamber 3 acoustic impedance Rh of
acoustic equalizer 4 Acoustic resistance Mh of the neck 8 Acoustic mass Ch of the neck 8 of the
acoustic equalizer 4 Acoustic capacity of the cavity 9 of the acoustic equalizer 4
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