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DESCRIPTION JPS63313999

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DESCRIPTION JPS63313999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker system having an acoustic tube on the back of the speaker unit. One of the prior art
techniques for expanding the bass range of prior art loudspeaker systems is the acoustic maze
form. Hereinafter, a conventional acoustic maze speaker system will be described with reference
to the drawings. FIG. 8 shows a sectional view of the above speaker system. In FIG. 8, 1 is a
cabinet, 21L, 2b. 20.2 + 1.26 is a partition plate provided on the front and back plates of the
cabinet 1, 3 is an opening provided on the bottom of the m1 face plate of the cabinet 1, 4 is a
speaker unit provided on the top of the front plate is there. The operation of the acoustic maze
speaker system configured as described above will be described below. Partition plate 21L
provided in the cabinet 1. 2b 120, 2d, and 261 constitute an acoustic pipe, and the sound
emitted from the rear surface of the speaker unit 4 is guided to the sound generator pipe and
emitted from the opening thereof. The acoustic tube resonates at a specific frequency determined
by its total length. Assuming that the sound velocity in the L1 air is C, the total length of the
acoustic tube is C, the resonant frequency / n, C / 4L * (2n + 1), n = n, 1, 2.
ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии ии Efficiency can be
improved. In addition, at the frequency at which the 1?2 wavelength of the sound tube is
mounted, the speaker emitted from the opening 3 of the sound tube which is inherently in
reverse phase to the sound emitted from the front of the speaker unit 4 and the sound from the
front The sound from the back of the unit 4 is added in phase due to the half wavelength phase
delay, and the sound pressure level increases. Further, when n = 2, acoustically enhanced sound
is emitted from the aperture 3 of the acoustic tube, as in the case of 3?4 wavelength n = o in the
acoustic tube. Therefore, a highly efficient speaker system can be realized in the low frequency
range. Problems to be Solved by the Invention However, in the configuration as described above,
the acoustic tube repeats resonance even at a frequency of n = 2 or more, and the middle and
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high sound of the rear surface of the speaker unit is radiated through the acoustic tube. This
sound frequently interferes with the sound on the front of the speaker unit to generate valleys
and peaks of sound pressure, and as shown in FIG. 9, the characteristics of the middle to high
range are significantly degraded and the sound quality is degraded. SUMMARY OF THE
INVENTION In view of the above problems, the present invention provides a speaker system in
which the sound pressure characteristic in the middle to high regions is flat as well as the activity
rate in the low frequency region is improved.
Means for Solving the Problem In order to achieve this object, the speaker system of the present
invention is provided with an acoustic tube which is continuously extended from the back of the
speaker unit and whose opening is open to the sound field space, In the tube, at least one boat
having a cross-sectional area smaller than the cross-sectional area of the acoustic tube is further
provided with a plurality of vias. In the present invention, at least one boat having a crosssectional area smaller than the cross-sectional area of the acoustic pipe is provided in the
acoustic pipe, and the acoustic field passes through the acoustic pipe by the reactance
component represented by the acoustic mass in the boat. The acoustically intercepts the midhigh range sound from the back of the speaker unit radiated to the boat, and the boat operates as
an acoustic filter that cuts off the high range. Also, if it is set to sound, from the vicinity of the
frequency where the 3/4 wavelength becomes approximately the same as the length of the
acoustic tube, the impedance is an actance component exhibited by the boat at the following
frequencies, so it does not operate as an acoustic filter. The presence of the boat has no effect on
the bass characteristic, and an effect as an acoustic filter can be obtained in a band higher than
this frequency. EXAMPLES Examples of the present invention will be described with reference to
the drawings. FIG. 1 shows a cross-sectional view of a speaker system according to a first
embodiment of the present invention. In FIG. 1, 6 is a cabinet, 6a-6? is a partition plate which
forms an acoustic pipe in the cabinet 6, 7 is a cross-sectional area of an acoustic pipe provided in
an acoustic pipe composed of partition plates 8 & -6e. It is supported by the shielding plate 8 by
a boat having a small cross-sectional area. An opening 9 is provided at the lower part of the front
plate of the cabinet 5, and the speaker unit 10 is provided at the upper part of the front plate o.
The operation of the speaker system configured as described above will be described below. The
partition plates e & 6e provided in the cabinet 5 constitute an acoustic pipe by the path from the
back surface of the speaker unit 10 to the opening 9, but in the acoustic pipe, the boat 7
supported by the shield plate 8 is provided There is. FIG. 2 shows a mechanical equivalent circuit
of the above speaker system. In the figure, F is the driving force, ZS is the impedance exhibited
by the speaker unit 1o, Zs is the impedance exhibited by the acoustic tube, C is the compliance
exhibited by the cavity formed by the boarder and the shielding plate 8 and the back of the
speaker unit 10, M Is a reactance exhibited by the air mass of the boat 7 and operates as a highfrequency cutoff filter having an arbitrary cutoff frequency according to the values of C and M.
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That is, since the air mass of the boat 7 moves as an actance component, when the frequency of
the sound passing through the boat 7 becomes high, the impedance becomes large, the high
range component flows to the compliance C, and the attenuated component from the acoustic
pipe opening 9 becomes It is emitted. On the other hand, in the low frequency range, the
impedance exhibited by the boat 7 is small, and the acoustic tube operates in the conventional
manner and radiates the low frequency range component from the gap 9 therebetween.
Therefore, if the high frequency cut-off frequency of the filter is set so that the wavelength
thereof is approximately 3/4 of the length L of the acoustic pipe, the efficiency wave number of
the bass band is conventionally boat using the resonance of the acoustic pipe. The presence of 7
does not affect the characteristics at all, and further frequencies are attenuated by the filter
effect, and there is less interference with the mid-high range radiated from the front of the
speaker unit 1 ░, as shown in FIG. As shown, substantially flat sound pressure characteristics
can be realized from the low range to the middle and high range. In the embodiment of FIG. 1,
the shape of the boat is a cylindrical tube and is supported by the shielding plate 8. However, as
shown in FIG. 4, the cross sectional shape from the acoustic tube to the boat 11 and the boat If
the cross-sectional shape leading to the sound tube is combined by a smooth area change, the
sound flow becomes continuous in the low frequency range where the wavelength is 3/4 or less
of the length of the sound tube, and the sound pressure level is attenuated. The filter effect can
be expected to be the same as that of the embodiment of FIG. 1 due to the reactance component
exhibited by the cylindrical portion of the boat. FIG. 6 shows a cross-sectional view of a speaker
system according to a second embodiment of the present invention. The same reference
numerals as in the first embodiment of FIG. 1 denote the same parts as in the first embodiment.
What is different in FIG. 6 is that the first boat 12 is supported by the shield plate 13 in the
acoustic pipe, and the second boat 15 is further supported by the shield plate 1? through the
space 14. The operation of the speaker system configured as described above will be described
below. FIG. 6 shows a mechanical equivalent circuit of the above speaker system. In the figure, C
is the compliance exhibited by the first port 12 and the vacant chamber formed by the shield
plate 13 and the back of the speaker unit 10, Ml is the reactance exhibited by the first boat 12,
and C1 is the first boat 12 and the shield. The compliance exhibited by the space 14 formed by
the plate 13, the second boat 15 and the shield plate 16, and M 2 is the reactance exhibited by
the second boat 15. In this circuit, C + * M + is further added to the circuit of the first
embodiment shown in FIG. 2 and the number of elements of the high-pass filter is increased.
Therefore, the middle and high tone range is cut off by a larger attenuation curve, and
interference between the middle and high tone emitted from the front surface of the speaker unit
1o and the middle and high tone emitted from the opening 9 of the acoustic tube is substantially
eliminated. It becomes possible. In addition, the impedance due to the reactance component
represented by J * M2 is low as in the first embodiment, and can be reproduced at a conventional
sound pressure level. In the second embodiment of the present invention shown in FIG. 6, the
positions of the first port and the second port are arranged substantially at the central axis of the
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cross section of the acoustic tube, but as shown in FIG. It is possible to effectively attenuate the
high-pass sound of a wavelength shorter than the diameter of the port passing through the port
once it is reflected to the shielding plate 16 if it is arranged so that they are mutually exclusive
from the central axis. It becomes. Further, in the present embodiment, the number of ports is two,
and the arrangement is made via an empty room. However, if the number of ports is further
increased, a more effective high-pass filter can be realized. As described above, according to the
present invention, an acoustic tube is provided on the back of the speaker unit, and a port having
a cross-sectional area smaller than the cross-sectional area of at least one acoustic tube is
provided in the acoustic tube. By configuring the cut-off filter, the bass tube enhancement effect
of the sound tube is maintained as it is, the sound pressure level is largely attenuated only in the
middle and high tone range, and the interference with the middle and high tone emitted from the
front of the speaker unit is eliminated. It is possible to realize a speaker system free from the
sound pressure characteristics of middle and high sound and no sound quality deterioration.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view of a speaker system according to a first embodiment of the
present invention, FIG. 2 is a mechanical equivalent circuit of the speaker system, FIG. 3 is a
sound pressure frequency characteristic diagram of the speaker system, FIG. FIG. 5 is a structural
sectional view of a speaker system having an improved port portion in the first embodiment of
the present invention, FIG. 5 is a structural sectional view of a speaker system according to a
second embodiment of the present invention, and FIG. Equivalent of the mechanical equivalent
circuit.
FIG. 7 is a structural sectional view of a speaker system in which the high frequency range filter
according to the second embodiment of the present invention is improved, FIG. 8 is a structural
sectional view of a conventional speaker system, and FIG. 9 is a sound pressure frequency of the
same speaker system FIG. 1.6 ииииииииии Cabinet, 2a to 26 + 82L to 6e
ииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии 7 , 11.12.15 и и и и и и и и и Port, 8t13, 16 и и и и и
Shielding plate, 14 и и и и и и Vacant. Name of agent Attorney Nakao Toshio and 1 other district
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