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JP2015222939

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DESCRIPTION JP2015222939
An object of the present invention is to increase distortion when performing loud and low
frequency band reproduction in a speaker system. A speaker system applies a first AC signal
having a frequency included in a first frequency band and a correction AC signal to a first
speaker unit to generate a first diaphragm of the first speaker unit. The second alternating
current signal as the first alternating current signal is converted to the second alternating current
signal as the first alternating current signal in a state where the second speaker unit as the first
speaker unit is attached to the closed cabinet having the same internal volume as the speaker
cabinet. The sound pressure reproduced by the vibration of the first diaphragm is equal to the
amplitude when the second diaphragm of the second speaker unit is vibrated by applying to the
speaker unit of The third AC signal having a frequency equal to or higher than the lowest
resonance frequency of the closed cabinet determined by the inner volume and the diameter of
the second speaker unit And a second sound pressure or under reproduced by vibration of the
diaphragm when applied. [Selected figure] Figure 1A
スピーカシステム
[0001]
The present disclosure relates to a speaker system using an open acoustic tube.
[0002]
In a car-mounted speaker system, in order to realize a powerful sound, it is desired to reproduce
at a sufficient volume up to the low range.
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Therefore, in the configuration in which the speaker unit is attached to the closed cabinet, the
sound pressure in the low frequency range is increased by electrically correcting the sound
pressure in the low frequency range to perform reproduction. For example, FIG. 9 shows a
conceptual diagram before and after the correction. FIG. 9 is a diagram showing sound pressure
characteristics with respect to frequency in the configuration in which the speaker unit is
attached to the closed cabinet. In the figure, the solid line indicates the sound pressure
characteristics with respect to the frequency when the sound pressure in the low band is
electrically corrected, and the dotted line indicates the sound pressure with respect to the
frequency when the sound pressure in the low band is not electrically corrected. Show the
characteristics. When electrically correcting the sound pressure in the low frequency range, the
middle or high frequency region is approximately achieved by electrically amplifying a band
lower than the resonant frequency of the closed cabinet, which is determined by the diameter of
the speaker unit and the internal volume of the closed cabinet. It plays the same sound pressure.
[0003]
However, when the low range is electrically amplified, the amplitude of the diaphragm of the
speaker unit also increases in proportion to the sound pressure. Therefore, the vibration mode
and the driving force of the diaphragm deviate from the linear region, and the distortion
contained in the reproduced sound increases, so that the target characteristics can not be
satisfied because the signal can not be sufficiently amplified. In addition, it is necessary to cut the
low frequency component of the sound source in which distortion is significantly generated by a
high pass filter. As a result, there is a problem that sufficient low-pass reproduction can not be
performed.
[0004]
The present disclosure is to solve the above-described conventional problems, and an object of
the present disclosure is to provide a speaker system that achieves high sound pressure
reproduction and low distortion reproduction at low frequencies.
[0005]
The speaker system of the present disclosure includes a speaker cabinet having an opening, a
first speaker unit attached to the speaker cabinet, and at least one acoustic tube whose ends are
open, and one end of the acoustic tube A first AC signal having a frequency included in a first
frequency band, and a first AC signal having a frequency located within the first frequency band,
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the second end of the acoustic tube being connected to the opening, A closed cabinet having the
same internal volume as that of the speaker cabinet when the first diaphragm of the first speaker
unit is vibrated by applying a correction AC signal having the same frequency as the signal to the
first speaker unit. The same second alternating current signal as the first alternating current
signal in a state in which the same second speaker unit as the first speaker unit is attached to the
Note: The sound pressure reproduced by the vibration of the first diaphragm in the case of
equalizing the amplitude when the second diaphragm of the second speaker unit is vibrated by
applying to the second speaker unit. In the case where a third alternating current signal having a
frequency equal to or higher than the minimum resonance frequency of the closed cabinet
determined by the inner volume of the closed cabinet and the aperture of the second speaker
unit is applied to the second speaker unit, An acoustic compliance which is equal to or less than a
sound pressure reproduced by the vibration of a second diaphragm, and the first frequency band
is determined by the acoustic mass of the acoustic tube and the internal volume of the speaker
cabinet excluding the volume of the acoustic tube It includes a first resonant frequency
determined by the component, and the first resonant frequency is smaller than the lowest
resonant frequency of the closed cabinet.
[0006]
According to the speaker system of the present disclosure, it is possible to provide a speaker
system capable of reproduction with high sound pressure and low distortion in a low frequency
band corresponding to the first frequency band. .
[0007]
FIG. 1A is a plan view of a speaker system according to a first embodiment of the present
disclosure.
FIG. 1B is a cross-sectional view of the speaker system in the first embodiment of the present
disclosure.
FIG. 2 is a diagram showing sound pressure frequency characteristics in the first embodiment of
the present disclosure.
FIG. 3 is a diagram showing amplitude frequency characteristics in the first embodiment of the
present disclosure. FIG. 4 is a diagram showing sound pressure frequency characteristics at the
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same amplitude in the first embodiment of the present disclosure. FIG. 5A is a plan view of a
speaker system according to a second embodiment of the present disclosure. FIG. 5B is a crosssectional view of the speaker system in the second embodiment of the present disclosure. FIG. 6
is a diagram showing an amplitude frequency characteristic in the second embodiment of the
present disclosure. FIG. 7 is a graph showing particle velocity characteristics in the second
embodiment of the present disclosure. FIG. 8 is a diagram showing the relationship between the
ratio of the acoustic tube volume to the total internal volume and the particle velocity inside the
acoustic tube in the second embodiment of the present disclosure. FIG. 9 is a conceptual view of
sound pressure frequency characteristics before and after electrical correction when the speaker
unit is attached to the closed cabinet.
[0008]
The speaker system of the present disclosure includes a speaker cabinet having an opening, a
first speaker unit attached to the speaker cabinet, and at least one acoustic tube whose ends are
open, and one end of the acoustic tube is The other end of the acoustic tube is connected to the
opening and has the same frequency as the first AC signal having the frequency included in the
first frequency band and the first AC signal When the correction AC signal is applied to the first
speaker unit to vibrate the first diaphragm of the first speaker unit, the amplitude is set to the
same as the first speaker unit in the closed cabinet having the same inner volume as the speaker
cabinet With the second speaker unit attached, a second AC signal identical to the first AC signal
is applied to the second speaker unit to provide a second speaker The sound pressure
reproduced by the vibration of the first diaphragm is equal to the internal volume of the closed
cabinet and the diameter of the second speaker unit when the second diaphragm of the unit is
made equal in amplitude to the vibration. When a third AC signal having a frequency equal to or
higher than the lowest resonance frequency of the closed cabinet determined is applied to the
second speaker unit, the sound pressure is equal to or less than the sound pressure reproduced
by the vibration of the second diaphragm, and the first frequency The band includes a first
resonant frequency determined by the acoustic mass of the acoustic tube and the acoustic
compliance component determined by the inner volume of the speaker cabinet excluding the
volume of the acoustic tube, the first resonant frequency being the lowest resonant frequency of
the enclosed cabinet Less than.
[0009]
Assuming that the first resonance frequency is a low frequency, a first AC signal having a
frequency included in the first frequency band is applied to the first speaker unit, and the first
vibration of the first speaker unit is generated. With the amplitude when the plate is vibrated, in
a state where the same second speaker unit as the first speaker unit is attached to the closed
cabinet, the same second alternating current signal as the first alternating current signal is sent
to the second speaker unit The amplitude can be smaller than the second amplitude when the
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second diaphragm of the second speaker unit is vibrated by application.
[0010]
Thus, in the first frequency band, there is room to increase the amplitude when the first
diaphragm is vibrated.
[0011]
In the configuration in which the same second speaker unit as the first speaker unit is attached to
the closed cabinet, the second diaphragm of the second speaker unit is used as the second
diaphragm to increase the sound pressure near the low frequency range. A correction AC signal
that oscillates at an amplitude greater than the amplitude must be applied to the second
loudspeaker unit.
[0012]
Thereby, in the closed cabinet, the distortion included in the sound pressure near the frequency
of the low frequency range is increased.
[0013]
In the present disclosure, when a correction AC signal that increases the amplitude of the first
speaker unit to the second amplitude is applied to the first speaker unit in the first frequency
band, the sound pressure of the low frequency band The distortion contained in is smaller than in
the case of providing the corrected AC signal to the second speaker unit, and the sound pressure
can be made higher.
[0014]
Therefore, the loudspeaker system of the present disclosure can provide a loudspeaker system
capable of reproducing with high sound pressure and low distortion in a low frequency band
corresponding to the first frequency band. .
[0015]
In the loudspeaker system of the present disclosure, the shape of the acoustic tube may be
helical.
[0016]
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With this configuration, a long acoustic pipe can be provided in the speaker cabinet, so that the
first resonance frequency can be set to a low frequency.
[0017]
The speaker system according to the present disclosure may configure an acoustic pipe by
connecting a spiral plate member disposed in a speaker cabinet and two inner wall surfaces
facing each other among the inner wall surfaces of the speaker cabinet. .
[0018]
By this configuration, since a long acoustic tube can be provided in the speaker cabinet, not only
the first resonance frequency can be set to a low frequency, but also the helical type disposed in
the speaker cabinet The plate-like member can also function as a reinforcing plate of the speaker
cabinet, and can prevent box noise of the speaker cabinet and increase rigidity.
[0019]
In the speaker system of the present disclosure, the spiral plate member may double as a
reinforcement of the speaker cabinet.
[0020]
With this configuration, it is not necessary to provide a speaker cabinet with a reinforcing
member separate from the spiral plate-like member.
[0021]
The speaker system of the present disclosure may be configured such that the shape of the
acoustic tube meanders in the cabinet.
[0022]
With this configuration, a long acoustic pipe can be provided in the speaker cabinet, so that the
first resonance frequency can be set to a low frequency.
[0023]
The speaker system of the present disclosure includes a first plate-like member in which one end
surface is connected to the first inner wall surface of the speaker cabinet, and a second inner
member of the speaker cabinet in which one end surface faces the first inner wall surface. And a
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second plate-like member connected to the wall surface, the first plate-like member being
disposed in a plurality with a gap therebetween, the first plate-like member facing one end face
of the first plate-like member The other end face of the plate-like member is located apart from
the second inner wall surface, and the second plate-like member is between adjacent first platelike members and adjacent to each other The other end face of the second plate-like member
located apart from each of the plate-like members of 1 and facing one end face of the second
plate-like member is located away from the first inner wall surface The first plate member and
the second plate member, respectively, of the inner wall surfaces of the speaker cabinet, A of the
inner wall may be configured acoustic tube by connecting different third inner wall surface and a
fourth interior wall surface and the first inner wall surface and the second inner wall surface.
[0024]
By this configuration, since a long acoustic tube can be provided in the speaker cabinet, not only
the first resonance frequency can be set to a low frequency, but also the helical type disposed in
the speaker cabinet The plate-like member can also function as a reinforcing plate of the speaker
cabinet, and can prevent box noise of the speaker cabinet and increase rigidity.
[0025]
In the speaker system of the present disclosure, the first plate-like member and the second platelike member may also serve as a reinforcement for the speaker cabinet.
[0026]
By configuring in this manner, it is not necessary to provide the speaker cabinet with a
reinforcing material separate from the first plate-like member and the second plate-like member.
[0027]
In the loudspeaker system of the present disclosure, the acoustic tube may partially reduce the
area of the cross section perpendicular to the longitudinal direction of the acoustic tube.
[0028]
The area of the cross section perpendicular to the longitudinal direction of the acoustic tube is
not partially reduced, that is, the same acoustic tube (referred to as a first acoustic tube)
everywhere in the area of the cross section perpendicular to the longitudinal direction When
comparing the acoustic tube (second acoustic tube) in which the area of the cross section
perpendicular to the surface is partially reduced, if the length of the first acoustic tube and the
length of the second acoustic tube are the same, The acoustic mass is larger for the second
02-05-2019
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acoustic tube than for the first acoustic tube.
[0029]
If the first and second acoustic tubes have the same length, the acoustic tube attached to the
speaker cabinet has a larger acoustic mass when the second acoustic tube is attached as
compared to the first acoustic tube. Therefore, the resonant frequency (first resonant frequency)
determined by the acoustic mass of the acoustic tube and the acoustic compliance determined by
the back volume of the speaker unit can be set to a lower value.
[0030]
Also, the resonance frequency set when the first acoustic pipe is used as the acoustic pipe
attached to the speaker cabinet, and the resonance frequency set when the second acoustic pipe
is used as the acoustic pipe attached to the speaker cabinet If they are the same, the length of the
second acoustic tube will be shorter than the length of the first acoustic tube.
Therefore, the second acoustic tube whose length is shorter than that of the first acoustic tube
can be used to have the same resonance frequency as when the first acoustic tube is used.
[0031]
In the speaker system of the present disclosure, the first frequency band is a frequency band of
16 to 45 Hz, and a first AC signal having a frequency near the first resonance frequency is
applied to the first speaker unit. The sound pressure reproduced by the vibration of the first
diaphragm and the sound reproduced by the vibration of the second diaphragm when the second
AC signal identical to the first AC signal is applied to the second speaker unit The pressure may
be substantially the same.
[0032]
In the speaker system of the present disclosure, the same means that the absolute value of
the difference between the sound pressure reproduced by the vibration of the first diaphragm
and the sound pressure reproduced by the vibration of the second diaphragm is within 1 dB. .
[0033]
In the speaker system of the present disclosure, the ratio of the inner volume of the acoustic tube
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to the inner volume of the speaker cabinet may be 5% or more.
[0034]
In the speaker system of the present disclosure, the second resonance frequency determined by
the length of the acoustic tube may substantially coincide with the peak frequency of the sound
pressure of the speaker unit attached to the speaker cabinet.
[0035]
By configuring in this way, it is possible to suppress the sharpness (Q) at the peak frequency of
the speaker unit, and it is possible to further flatten the characteristics at the peak frequency of
the speaker unit.
[0036]
In the speaker system of the present disclosure, the sound absorbing material may be disposed in
a part of the acoustic pipe.
[0037]
With such a configuration, it is possible to reduce a sudden change (dip) in the amplitude
characteristic of the diaphragm of the speaker unit in the vicinity of the second resonance
frequency determined by the length of the acoustic tube.
[0038]
In the loudspeaker system of the present disclosure, the acoustic tube may constitute a wall
around the loudspeaker cabinet.
[0039]
The speaker system of the present disclosure applies the same AC signal having a frequency of a
second frequency lower than the lowest resonance frequency and different from the first
frequency band to each of the first speaker unit and the second speaker unit. When this happens,
the sound pressure of the sound reproduced by the vibration of the first diaphragm and the
sound pressure of the sound reproduced by the vibration of the second diaphragm may be
substantially the same.
[0040]
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9
In the speaker system of the present disclosure, the same means that the absolute value of
the difference between the sound pressure reproduced by the vibration of the first diaphragm
and the sound pressure reproduced by the vibration of the second diaphragm is within 1 dB. .
[0041]
Hereinafter, embodiments of the present disclosure will be described with reference to the
drawings.
(First Embodiment) FIG. 1A is a plan view in which a part of a speaker system according to a first
embodiment of the present disclosure is cut away.
FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A.
[0042]
The speaker system is provided on the speaker cabinet 1, the speaker unit 8 attached to the front
plate 2 of the speaker cabinet 1, the partition plate 11 provided inside the speaker cabinet 1, and
the side plate 6 of the speaker cabinet 1 And the opening 12 being formed.
[0043]
The speaker cabinet 1 includes a front plate 2 to which a speaker unit 8 (first speaker unit) is
attached, a side plate 6 provided with an opening 12, and three other side plates 3 and side
plates A side plate 5, a back plate 7, and a partition plate 11 provided inside the speaker cabinet
1 are provided.
The surfaces of the front plate 2, the side plate 3, the side plate 4, the side plate 5, the side plate
6 and the back plate 7 located outside the speaker cabinet 1 constitute an outer frame of the
speaker cabinet 1.
The outer frame of the speaker cabinet 1 has a hexahedron shape.
02-05-2019
10
Each surface of the front plate 2, the side plate 3, the side plate 4, the side plate 5, the side plate
6, and the back plate 7 located inside the speaker cabinet 1 is an inner wall (or an inner wall
surface) of the speaker cabinet 1. Configure.
[0044]
The partition plate 11 has a spiral shape along the side plate 3, the side plate 4, the side plate 5,
and the side plate 6.
The partition plate 11 is connected (or joined) to two of the inner wall surfaces of the speaker
cabinet 1 facing each other.
For example, the partition plate 11 is connected to the front plate 2 and the back plate 7 inside
the speaker cabinet 1.
The end of the partition plate 11 is connected to the vicinity of the end of the side plate 6 inside
the speaker cabinet 1.
The partition plate 11 may be formed in a spiral shape by connecting the ends of a plurality of
plate-shaped members, or a spiral-shaped plate-shaped member may be used.
Further, when the spiral shaped partition plate 11 is integrally formed with the side surface plate
3, the side surface plate 4, the side surface plate 5 and the side surface plate 6, the outermost
periphery of the spiral shaped partition plate 11 is the side surface plate 3 side. The face plate 4,
the side plate 5, and the side plate 6 are provided.
[0045]
The speaker cabinet 1 is formed by the spiral shaped inner and outer partitions 11, the front
panel 2, the rear panel 7 or the partition 11, the side panels 3, the side panels 4, the side panels
5, the side panels 6, the front panel 2 and the rear panel 7. A helical-shaped acoustic tube 10 is
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11
configured in the inside.
The acoustic tube 10 configured in this way is open at both ends.
One opening (or one end) of the acoustic tube 10 is located in the back volume 9 of the speaker
unit 8.
Further, the other opening (or the other end) of the acoustic tube 10 is connected to the opening
12 provided in the side plate 6.
[0046]
The rear volume 9 of the speaker unit 8 and the outside of the speaker cabinet 1 (outside of the
Spica system) are connected via the acoustic tube 10 and the opening 12.
The rear volume 9 is an internal space of the speaker cabinet 1 located behind the speaker unit
8.
The rear volume 9 does not include the space in the speaker cabinet 1 in which the acoustic tube
is disposed.
Accordingly, the rear volume 9 is an internal space of the speaker cabinet 1 excluding the space
where the acoustic tube is disposed.
[0047]
The speaker system of the first embodiment has, for example, two resonance frequencies.
One is a resonant frequency determined by the acoustic mass of the acoustic tube 10 and the
acoustic compliance determined by the back volume of the speaker unit 8, and the other is a
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resonant frequency determined by the length of the acoustic tube 10.
The rear volume of the speaker unit 8 is the volume of the space corresponding to the rear
volume 9.
That is, the rear volume of the speaker unit 8 is the internal volume of the speaker cabinet 1
excluding the volume of the acoustic tube 10.
[0048]
In the following description, the resonance frequency determined by the acoustic mass of the
acoustic tube 10 and the acoustic compliance determined by the back volume of the speaker unit
8 in the speaker system of Embodiment 1 will be described as a first resonance frequency.
Further, the resonance frequency determined by the length of the acoustic tube 10 in the speaker
system of the first embodiment will be described as a second resonance frequency.
[0049]
The operation of the loudspeaker system configured as described above will be described.
When an AC signal (for example, AC voltage or AC current) is applied to the speaker unit 8, a
diaphragm (first diaphragm: not shown) included in the speaker unit 8 vibrates to reproduce
sound.
The reproduced sound is radiated to the outside of the speaker cabinet 1.
At this time, the reproduced sound is also radiated to a rear volume 9 which is an internal space
of the speaker cabinet 1 which is a rear surface of the diaphragm.
02-05-2019
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[0050]
The sound radiated to the internal space of the speaker cabinet 1 is propagated inside the
acoustic tube 10.
Of the sound propagated inside the acoustic tube 10, only the sound radiated by the vibration of
the diaphragm according to the AC signal having a frequency near the first resonance frequency
is a speaker through the acoustic tube 10 and the opening 12 It is radiated to the outside of the
cabinet 1.
[0051]
In order to explain the effect of the speaker system of Embodiment 1, the same speaker unit as
the speaker unit 8 (second speaker in a closed cabinet having an inner volume obtained by
adding the back volume of the speaker unit 8 and the inner volume of the acoustic tube 10 The
unit is compared with the attached speaker system (referred to as a speaker system to be
compared).
The internal volume of the closed cabinet is equal to the internal volume of the speaker cabinet
1.
This closed cabinet does not have the acoustic tube 10 (especially the partition plate 11) as
shown in FIG. 1 inside.
The speaker system to be compared has a resonant frequency determined by the diameter of the
speaker unit attached to the closed cabinet and the inner volume of the closed cabinet.
[0052]
In the following description, in the speaker system to be compared, the resonance frequency
determined by the diameter of the speaker unit attached to the closed cabinet and the inner
volume of the closed cabinet will be referred to as the minimum resonance frequency of the
closed cabinet.
02-05-2019
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[0053]
In the speaker system of the first embodiment, the acoustic mass of the acoustic tube 10 and the
rear volume of the speaker unit 8 are designed such that the first resonance frequency is smaller
than the lowest resonance frequency of the closed cabinet.
The acoustic mass of the acoustic tube 10 depends, for example, on the length and crosssectional area of the acoustic tube 10.
Therefore, if one of the length and the cross-sectional area of the acoustic tube 10 is changed,
the acoustic mass of the acoustic tube 10 changes accordingly.
[0054]
The inner dimensions of the speaker cabinet 1 shown in FIGS. 1A and 1B are 307 mm long ×
366 mm wide × 65 mm high.
The internal volume of the speaker cabinet 1 is a value obtained by adding the volume of the rear
volume 9 and the internal volume of the acoustic tube 10. In this example, the total internal
volume of the speaker cabinet 1 is 5 liters (L).
The speaker unit 8 is an electrodynamic speaker having a diameter of 16 cm.
The cross section of the acoustic tube 10 is 65 mm long × 11 mm wide, and 2 m in length.
The ratio of the internal volume of the acoustic tube 10 to the total internal volume is 28%.
[0055]
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15
In such a configuration, the first resonance frequency in the speaker system of Embodiment 1 is
16 Hz. On the other hand, the lowest resonance frequency in the closed cabinet created in
consideration of the above values is 70 Hz.
[0056]
When an alternating current signal having the same amplitude is applied to each of the speaker
unit 8 of the speaker system of the first embodiment and the speaker unit of the speaker system
to be compared, FIG. It is a figure which shows the relationship (sound pressure frequency
characteristic) with the sound pressure (SPL: Sound Pressure Level) of the sound radiated ¦
emitted from a diaphragm. In FIG. 2, the horizontal axis is the frequency of the AC signal to be
applied, and the vertical axis is the sound pressure of the speaker system.
[0057]
The speaker unit 8 (first speaker unit) of the speaker system according to the first embodiment
and the speaker unit (second speaker unit) of the speaker system to be compared are the same
speaker unit.
[0058]
When alternating current signals having the same amplitude are applied to each of the speaker
unit 8 of the speaker system of Embodiment 1 and the second speaker unit of the speaker system
to be compared, FIG. It is a figure which shows the relationship (amplitude frequency
characteristic) with the amplitude of the diaphragm of a speaker unit.
In FIG. 3, the horizontal axis is the frequency of the AC signal to be applied, and the vertical axis
is the amplitude of the diaphragm of the speaker unit (specifically, the value obtained by
calculating the logarithm of the amplitude).
[0059]
From the amplitude characteristics (solid line) of the diaphragm of the second speaker unit of the
speaker system to be compared, the amplitude of the second diaphragm below the lowest
resonance frequency of the closed cabinet (in this example, 70 Hz or less) is substantially
constant. I understand that there is.
02-05-2019
16
[0060]
Therefore, in the speaker system to be compared, in order to amplify the sound pressure below
the lowest resonance frequency of the closed cabinet, it is necessary to increase the amplitude of
the second diaphragm of the second speaker unit.
[0061]
On the other hand, in the speaker system of Embodiment 1 (the speaker system in which the
speaker unit 8 is attached to the speaker cabinet 1), the first resonance frequency is a frequency
smaller than the lowest resonance frequency of the closed cabinet (16 Hz in this example) It is
designed to be
[0062]
From FIG. 3, in the speaker system of Embodiment 1, an AC signal having a frequency included in
a first frequency band including a first resonance frequency (in this example, 16 Hz to 45 Hz,
more preferably 16 Hz to 30 Hz) It can be understood that the amplitude of the diaphragm of the
speaker unit 8 is smaller than the amplitude of the second diaphragm of the second speaker unit
in the speaker system to be compared.
[0063]
Next, the sound pressure frequency characteristics (dotted line) of the speaker system in the first
embodiment shown in FIG. 2 and the sound pressure frequency characteristics (solid line) of the
speaker system to be compared have similar characteristics.
In particular, in the first frequency band described above, the absolute value of the difference
between the sound pressures of the two is within 1 dB, and the characteristics of the two are
considered to be substantially the same.
In addition, since the absolute value of the difference between the two characteristics is within 1
dB in the second frequency band (for example, 45 Hz to 65 Hz) which is smaller than the lowest
resonance frequency and different from the above first frequency band, The characteristics are
considered to be substantially the same.
02-05-2019
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[0064]
From the sound pressure characteristics shown in FIG. 2, in the case where the same speaker unit
is attached to the speaker cabinet 1 of the first embodiment and the case where the same
speaker unit is attached to the closed cabinet, AC signals of the same frequency and the same
amplitude are respectively applied For example, in terms of sound pressure characteristics with
respect to frequency, it is considered that there is no significant difference between the two.
[0065]
Further, FIG. 2 shows sound pressure characteristics of second-order distortion and third-order
distortion included in the sound reproduced in the speaker system in the first embodiment and
the speaker system to be compared.
Sound pressure frequency characteristics of the speaker system in the first embodiment, the
speaker system in the comparison object, and the second order distortion in the first frequency
band from the sound pressure frequency characteristics of the third order distortion It can be
understood that the sound pressure is lower than the second-order distortion and the third-order
distortion in the speaker system to be compared.
[0066]
Therefore, it can be said that the speaker system in the first embodiment is superior to the
speaker system to be compared in terms of reducing distortion of reproduced sound (or in terms
of low distortion reproduction).
[0067]
On the other hand, the amplitude characteristics of the diaphragm (first diaphragm) of the
loudspeaker unit 8 (first loudspeaker unit) in the loudspeaker system of Embodiment 1 shown in
FIG. 3 and the second loudspeaker unit of the loudspeaker system to be compared As shown by
the amplitude characteristics of the diaphragm (second diaphragm), the amplitudes of the two in
the second frequency band (45 Hz to 65 Hz) lower than the lowest resonance frequency (70 Hz)
of the closed cabinet are substantially the same.
02-05-2019
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On the other hand, in the first frequency band, it can be understood that the amplitude
characteristics of the two are largely different.
[0068]
In the speaker system to be compared shown in FIG. 3, it can be understood that the amplitude of
the second diaphragm is substantially constant in the first frequency band.
[0069]
As described above, the closed cabinet does not have the acoustic tube 10.
Thus, the loudspeaker system to be compared does not resonate at the first resonant frequency.
Therefore, it can be understood that no noticeable change occurs even if an alternating current
signal having a frequency near the first frequency is applied to the second speaker unit.
[0070]
On the other hand, in the speaker system of the first embodiment, the resonance is designed to
occur at the first resonance frequency.
Therefore, when an alternating current signal having a frequency included in the first frequency
band (in particular, a frequency near the first resonance frequency) is applied to the first speaker
unit, the amplitude of the first speaker unit is the same alternating current. It can be understood
that the amplitude is smaller than the amplitude of the second speaker unit when the signal is
applied to the second speaker unit.
[0071]
From the above, in the first frequency band, the amplitude of the diaphragm of the loudspeaker
unit 8 (first loudspeaker unit) of the loudspeaker system in the first embodiment is the second
loudspeaker of the loudspeaker system to be compared. It can be understood that the amplitude
of the diaphragm of the unit is smaller.
02-05-2019
19
[0072]
The inventors employ the configuration of the speaker system according to the first embodiment,
and in the first frequency band, the amplitude of the diaphragm (first diaphragm) of the speaker
unit 8 (first speaker unit) is It was noted that there is a margin that can be made large enough to
be equal to the amplitude of the diaphragm (second diaphragm) of the second speaker unit of the
speaker system to be compared.
[0073]
That is, in the first frequency band, the speaker unit 8 when the AC signal (first AC signal)
including the frequency included in the first frequency band is applied to the speaker unit 8 of
the speaker system of the first embodiment. The vibration of the second speaker unit when the
same amplitude signal value of the diaphragm and the same AC signal (second AC signal) as the
first AC signal are applied to the second speaker unit of the speaker system to be compared What
is different from the value of the plate amplitude is as described with reference to FIG.
[0074]
For example, an alternating current signal (a corrected alternating current signal) which is an
alternating current signal including the first resonance frequency and equal to the value of the
amplitude of the diaphragm of the second speaker unit is transmitted to the speaker unit 8
together with the first alternating current signal. If applied, the value of the amplitude of the
diaphragm of the speaker unit 8 at the first resonance frequency can be increased.
[0075]
This holds true not only for AC signals containing the first resonance frequency, but also for AC
signals containing a frequency of the first frequency band (in this example, 16 Hz to 45 Hz,
preferably 16 Hz to 30 Hz). .
[0076]
At this time, distortion generated when the value of the amplitude of the diaphragm of the
speaker unit 8 is increased can be smaller than distortion generated when the value of the
amplitude of the diaphragm of the second speaker unit is increased.
[0077]
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Also, if the value of the amplitude of the diaphragm of the speaker unit 8 in the first frequency
band is increased, the sound pressure of the speaker unit 8 in the first frequency band is
increased.
Therefore, the sound pressure characteristic of the first frequency band corresponding to the low
frequency band of the speaker system of the first embodiment is improved.
[0078]
FIG. 4 is a diagram showing sound pressure frequency characteristics (dotted line) when the
correction AC signal is applied to the speaker unit 8 together with the first AC signal in the first
frequency band in the speaker system according to the first embodiment. is there.
Further, FIG. 4 shows the characteristic of the acoustic impedance to the frequency in the
speaker system to be compared, and the sound pressure characteristic to the frequency in the
speaker system to be compared shown in FIG.
Further, as shown in FIG. 4, from the acoustic impedance characteristic with respect to the
frequency of the closed cabinet, it is indicated that the lowest resonance frequency of the closed
cabinet is around 70 Hz.
[0079]
As shown in FIG. 4, in the first frequency band, a speaker unit that corrects the alternating
current signal having the same frequency as the frequency of the first alternating current signal
together with the first alternating current signal having the frequency included in the first
frequency band It can be understood that the sound pressure characteristic in the first frequency
band is improved in the speaker system according to the first embodiment because the voltage is
applied to V.8.
[0080]
The sound pressure near the first resonance frequency (70 dB in this example) is an AC signal
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(third AC signal) having the same amplitude as the first AC signal as the speaker unit 8 (or the
second speaker unit). Smaller than the sound pressure (90 dB in this example) applied to the
At this time, the third AC signal has a frequency equal to or higher than the lowest resonance
frequency of the closed cabinet (70 Hz or higher in this example).
This is because the reproduction sound pressure in the first band does not require a sound
pressure higher than the reproduction sound pressure in the band higher than the lowest
resonance frequency.
[0081]
Therefore, the speaker system according to the first embodiment can improve the sound
pressure characteristic of the low frequency band (16 Hz to 45 Hz in this example) by applying
the correction AC signal in the first frequency band. .
[0082]
As described above, the speaker system of the first embodiment adjusts the acoustic compliance
determined by the acoustic mass of the acoustic tube 10 and the back volume of the speaker unit
8 to reduce the resonance frequency (the first frequency) in the low frequency band. It has a
great feature in that it is configured to have a resonant frequency.
[0083]
By configuring in this way, it is possible to allow a margin to increase the amplitude of the
diaphragm of the speaker unit 8 without any problem in the low frequency band.
Thereby, by applying the correction AC signal to the speaker unit 8, the sound pressure
characteristic of the low frequency band corresponding to the first frequency band can be
improved.
[0084]
Therefore, compared with the speaker system which attached the same speaker unit as speaker
unit 8 to the closed cabinet which has the volume which added the back volume of speaker unit
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8 and the inner volume of sound pipe 10 compared with the speaker system of this embodiment
In the low frequency band, high sound pressure and low distortion can be reproduced.
[0085]
Moreover, the speaker system in the comparison object uses a closed cabinet.
In the case of a closed cabinet, reinforcements need to be provided inside the cabinet in order to
prevent ringing and to increase rigidity.
However, in the speaker system according to the first embodiment, the structure of the acoustic
tube 10 (in particular, the structure in which the partition plate 11 is disposed in a spiral and the
partition plate 11 is connected to the front plate 2 and the back plate 7) is a reinforcement. In
order to be able to double as an effect, it is not necessary to provide a special reinforcing
material for reinforcing the speaker cabinet 1.
[0086]
In addition, resonance of the acoustic tube 10 occurs at a frequency at which the length of the
acoustic tube 10 is a half wavelength.
As a result, the amplitude at that frequency is suppressed and the sound pressure is also reduced.
For example, when the length is 2 m as in the case of the acoustic tube 10 in the first
embodiment, the resonance of the acoustic tube 10 occurs at 85 Hz. Looking at the 85 Hz
characteristics in FIGS. 2 and 3, both the sound pressure and the amplitude decrease.
[0087]
Although not used in the first embodiment, for example, when a peak is included in the
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23
characteristics of the speaker unit 8, the peak is reduced by matching the peak frequency with
the resonant frequency of the acoustic tube 10, and the sound pressure frequency characteristic
is flat. I can improve the sex. This is also effective for the peak characteristics that occur when
the speaker unit 8 is attached to the cabinet.
[0088]
Also, each of a resonance frequency (first resonance frequency) determined by the acoustic
compliance determined by the back volume of the speaker unit 8 and the acoustic mass of the
acoustic tube 10 and a resonance frequency (second resonance frequency) determined by the
length of the acoustic tube 10 In order to set the frequency to the target frequency, the crosssectional area of the acoustic tube 10 may be partially changed. As a result, the second
resonance frequency can be changed without changing the acoustic compliance determined by
the rear volume of the speaker unit 8 and the first resonance frequency.
[0089]
Further, in the acoustic tube 10 of the present embodiment, the area of the cross section
perpendicular to the longitudinal direction of the acoustic tube is not partially reduced, that is,
the area of the cross section perpendicular to the longitudinal direction of the acoustic tube 10 is
everywhere. The explanation is given using the same as an example. Such an acoustic tube is
referred to as a first acoustic tube. However, it is not limited to this. For example, what reduced a
part of cross-sectional area of the cross section perpendicular ¦ vertical to the length direction of
the acoustic tube 10 may be used as an acoustic tube. Such an acoustic tube is referred to as a
second acoustic tube. When comparing the first acoustic tube and the second acoustic tube,
when the lengths are the same, the acoustic mass of the second acoustic tube is larger than the
acoustic mass of the first acoustic tube.
[0090]
As described above, in the speaker system of the present embodiment, resonance occurs at a
resonance frequency (first resonance frequency) determined by the acoustic mass of the acoustic
tube 10 and the acoustic compliance determined by the back volume of the speaker unit 8.
[0091]
In the case where the length of the acoustic tube 10 mounted in the speaker cabinet 1 is limited,
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when the first acoustic tube is used as the acoustic tube 10, the resonant frequency lower than
the resonant frequency corresponding to the limited value of the length is In some cases, it can
not be set as the resonance frequency of 1.
[0092]
As long as the first acoustic pipe and the second acoustic pipe have the same length, the acoustic
tube 10 attached to the speaker cabinet 1 has an acoustic mass in which the second acoustic
pipe is attached as compared to the first acoustic pipe. Of the first resonance frequency can be
set lower than in the case of attaching the first acoustic tube.
[0093]
Moreover, it is set when using the 2nd acoustic pipe as a resonance frequency set when using a
1st acoustic pipe as acoustic pipe 10 attached to the speaker cabinet 1, and the acoustic pipe 10
attached to the speaker cabinet 1 If the resonant frequency is the same, the length of the second
acoustic tube is shorter than the length of the first acoustic tube.
Therefore, the second acoustic pipe whose length is shorter than that of the first acoustic pipe
can be used to have the same resonance frequency as when the first acoustic pipe is used.
[0094]
When the first acoustic tube as described above is used as the acoustic tube 10, the resonance
frequency determined by the length of the acoustic tube 10 is higher as the length thereof is
shorter.
Therefore, if the sound pressure frequency characteristics do not include peaks and it is not
necessary to suppress them, the second resonance frequency (the length of the sound tube 10
outside the reproduction band of the speaker system can be reduced by shortening the length of
the sound tube 10 It is desirable to set the resonance frequency determined by
[0095]
In the first embodiment, a unit of an electrodynamic system is used as the speaker unit 8, but a
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unit of another drive system such as a piezoelectric system may be used.
[0096]
Moreover, although the above-mentioned acoustic tube 10 was comprised with one acoustic
tube, you may comprise with a several acoustic tube.
For example, even if a speaker system is configured using two acoustic tubes whose crosssectional area is half the length of the acoustic tube 10 of the first embodiment and the length is
the same as the length of the acoustic tube 10 of the first embodiment. Almost the same effect as
the speaker system of the first embodiment can be obtained.
[0097]
Second Embodiment FIG. 5A is a plan view in which a part of a speaker system according to a
second embodiment of the present disclosure is cut away.
FIG. 5B is a cross-sectional view taken along line 5B-5B of FIG. 5A.
[0098]
The speaker system includes the speaker cabinet 100, the speaker unit 8 attached to the front
plate 102 of the speaker cabinet 100, the partition plate 111a and the partition plate 111b
provided inside the speaker cabinet 100, and the side of the speaker cabinet 100 It is comprised
by the opening part 112 provided in the face plate 105. FIG.
[0099]
The speaker cabinet 100 includes a front plate 102 to which the speaker unit 8 is attached, a
side plate 105 provided with an opening 112, and other three side plates 103, 104 and 106. A
rear plate 107, a partition plate 111a (a first plate-like member) provided inside the speaker
cabinet 100, and a partition plate 111b (a second plate-like member) are provided.
[0100]
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One end face of the partition plate 111 a is further connected to the side plate 105 (the first
inner wall surface of the speaker cabinet 100) on the inner side of the speaker cabinet 100.
Further, one end face of the partition plate 111 b is further connected to the side plate 106 (the
second inner wall surface of the speaker cabinet 100) on the inner side of the speaker cabinet
100.
The partition plate 111 a and the partition plate 111 b are respectively connected to the front
plate 102 (the third inner wall surface of the speaker cabinet 100) on the inner side of the
speaker cabinet 100. Further, the partition plate 111 a and the partition plate 111 b are
respectively connected to the back plate 107 (the fourth inner wall surface of the speaker cabinet
100) on the inner side of the speaker cabinet 100. Thereby, the partition plate 111 a and the
partition plate 111 b also serve as the reinforcing material of the speaker cabinet 100.
[0101]
In the speaker system shown in FIGS. 5A and 5B, a plurality of partition plates 111a is provided.
Moreover, in the speaker system shown to FIG. 5A and FIG. 5B, the partition plate 111b has
multiple.
[0102]
For example, the distance between adjacent partition plates 111a and the distance between
adjacent partition plates 111b are the same. Further, for example, it is assumed that the
thickness of the partition plate 111a and the thickness of the partition plate 111b are the same.
Moreover, the space ¦ interval of the adjacent partition plate 111a and the partition plate 111b is
the same, respectively. The distance between the adjacent partition plates 111a is larger than the
thickness of the partition plate 111b. And the space ¦ interval of the adjacent partition plate
111b and the space ¦ interval of the side plate 103 and the partition plate 111b nearest to the
side plate 103 are larger than the thickness of the partition plate 111a.
[0103]
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The partition plate 111 a is positioned between the adjacent partition plates 111 b and between
the side surface plate 103 and the partition plate 111 b closest to the side surface plate 103. At
this time, the end surface (the other end surface) facing the end surface (one end surface) on the
side where the partition plate 111 a is connected to the side surface plate 105 on the inner side
of the speaker cabinet 100 Located away. Further, the end surface (the other end surface) facing
the end surface (one end surface) of the side where the partition plate 111 b is connected to the
side surface plate 106 at the inner side of the speaker cabinet 100 is separated from the side
surface plate 105 at the inner side of the speaker cabinet 100 Located.
[0104]
With this configuration, the inside of the speaker cabinet 100 is meandered by the partition plate
111a, the partition plate 111b, the front plate 102, the back plate 107, the side plate 103, the
side plate 105, and the side plate 106. The acoustic tube 110 is configured. One opening of the
acoustic tube 110 is located in the rear volume 109 of the speaker unit 8, and the other opening
is connected to the opening 112 provided between the end of the side plate 105 and the side
plate 103. It is done.
[0105]
The operation of the loudspeaker system configured as described above is substantially the same
as that of the first embodiment. The difference is in the configuration position of the acoustic
tube 110.
[0106]
In the speaker cabinet 1 according to the first embodiment, the helical acoustic tube 10 is
provided with the spiral partition plate 11 formed along the four sides of the side plate 3, the
side plate 4, the side plate 5, and the side plate 6. Formed.
[0107]
On the other hand, in the second embodiment, as shown in FIG. 5A, one end of the partition plate
02-05-2019
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111a is connected to the side surface plate 105, and one end of the partition plate 111b is
connected to the side surface plate 106.
Therefore, the rigidity of the speaker cabinet 100 is further improved as compared with the first
embodiment, and unnecessary sound from the speaker cabinet 100 due to the vibration of the
speaker unit 8 is suppressed.
[0108]
In the second embodiment, as in the first embodiment, the total internal volume of the back
volume 109 and the internal volume of the acoustic tube 110 is 5 liters. The speaker unit 8 is an
electrodynamic speaker having a diameter of 16 cm. The cross section of the acoustic tube 110
is 65 mm long × 11 mm wide, and 2 m in length. The ratio of the internal volume of the acoustic
tube 110 to the total internal volume is 28%.
[0109]
With the above configuration, the resonance frequency determined by the acoustic mass of the
acoustic tube 110 and the acoustic compliance component of the rear volume 109 of the speaker
unit 8 is set to 16 Hz. The sound pressure characteristics and the amplitude characteristics with
respect to the frequency in the speaker system of the second embodiment are the same as those
shown in FIGS.
[0110]
A configuration in which the resonance frequency is set to 16 Hz under the condition of the
entire cabinet volume 5L using the speaker unit 8 is present other than the 2 m acoustic tube
110 described above. For example, when the cross-sectional area of the acoustic tube 110 is
equivalent to φ 9.5 mm, the length of the acoustic tube 110 can be realized with 16 cm. The
ratio of the internal volume of the acoustic tube 110 to the total internal volume of the speaker
cabinet 100 in that case is 0.3%.
[0111]
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In the low frequency band of 100 Hz or less, the sound pressure frequency characteristics
substantially match except for the characteristic of 85 Hz which is the resonance frequency of
the acoustic tube 110.
[0112]
FIG. 6 shows the amplitude of the speaker unit 8 in a speaker system having an acoustic pipe
length of 2 m and 16 cm.
In the figure, the solid line shows the amplitude frequency characteristic when using a 0.16 m
long acoustic tube in the speaker system according to the present embodiment, and the dotted
line shows the sound in the speaker system according to the present embodiment. An amplitude
frequency characteristic at the time of using an acoustic pipe with a pipe length of 2 m is shown.
Even if the acoustic pipe 110 is configured to have the same 16 Hz, the amplitude at the
resonance frequency of 16 Hz is smaller when the acoustic pipe length is 2 m. This is considered
to be because the viscosity of the air increased because the cross-sectional area of the acoustic
tube 110 decreased.
[0113]
As a result, when compared as the reproduction sound pressure in the case of the same
amplitude, the reproduction sound pressure is larger in the speaker system of the second
embodiment in which the length of the acoustic tube 110 is 2 m.
[0114]
In addition, particle velocities generated in the acoustic tubes 110 of 2 m and 16 cm in acoustic
pipe length are compared.
FIG. 7 shows particle velocity characteristics in the acoustic tube 110 at 16 Hz.
[0115]
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A particle velocity of 16 cm in acoustic pipe length is approximately 10 times as high as that of
the acoustic pipe 110 of the second embodiment. As a result, wind noise is generated in the
speaker system having an acoustic pipe length of 16 cm. That is, it can be seen that with the
acoustic pipe length of 16 cm, even if the resonance frequency can be 16 Hz, the speaker system
does not have good characteristics.
[0116]
Therefore, from the condition that particle velocity in the acoustic tube 110 and wind noise do
not occur, the ratio of the inner volume of the acoustic tube 110 to the total inner volume of the
speaker cabinet 100 is 5% or more to use as a speaker system is necessary.
[0117]
Further, FIG. 8 shows the relationship between the ratio of the acoustic tube volume to the total
internal volume and the particle velocity inside the acoustic tube.
As understood from this result, when the ratio of the inner volume of the acoustic tube is less
than 5%, the value of the particle velocity inside the acoustic tube rapidly increases. Therefore,
the ratio of the inner volume of the acoustic tube to the total inner volume of the speaker cabinet
is required to be 5% or more.
[0118]
The thickness of the partition plate in the first and second embodiments may be any value as
long as the rigidity of the speaker cabinet can be secured using the partition plate.
[0119]
Moreover, although the acoustic pipe 110 is connected with the front plate 102 and the back
plate 107 to which the partition plate 111a, the partition plate 111b, and the speaker unit 8
were attached, it is not limited to this.
For example, a plurality of partition plates may be connected in the shape of a tube to constitute
an acoustic tube having a meandering shape. In that case, it is desirable to give priority to the
02-05-2019
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aspect ratio of the acoustic tube cross section. For example, when a plurality of partition plates
are connected to form a tube, and an acoustic tube having a meandering shape is used, such an
acoustic tube is used as the side plate 103, the side plate 104, the side plate 105, and the side
plate 106. It may be disposed along the inner wall surface. In the meandering shape of the
acoustic tube, the continuity of the particle velocity inside the acoustic tube is improved by
making the shape of the inner wall of the portion to be folded back by the meandering into a
curved shape (a shape that takes R).
[0120]
Further, as in the first embodiment, when the characteristics of the speaker unit include a peak, it
is possible to reduce the peak by matching the peak frequency with the resonance frequency of
the acoustic tube.
[0121]
In addition, by disposing the sound absorbing material inside the acoustic pipe (for example, at
the cabinet side entrance portion), it is possible to reduce a sharp change (dip) in the amplitude
characteristic in the vicinity of the second resonance frequency determined by the length of the
acoustic pipe .
[0122]
In the second embodiment, the cross-sectional area of the acoustic tube 110 is fixed, but R may
be provided in the shape of the opening.
It leads to the reduction of wind noise.
[0123]
Although the speaker system according to the embodiment has been described above with
reference to the drawings, the present invention is not limited to the illustrated embodiment.
Various modifications and variations can be made to the illustrated embodiment within the same
or equivalent scope of the present invention.
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[0124]
The present disclosure can be applied as a speaker system characterized by low-frequency
reproduction such as in-vehicle and TV.
[0125]
REFERENCE SIGNS LIST 1, 100 speaker cabinet 2, 102 front plate 3, 4, 5, 6, 103, 104, 105, 106
side plate 7, 107 rear plate 8 speaker unit 9, 109 rear volume portion 10, 110 acoustic tube 11,
111 a, 111b partition plate 12, 112 opening
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