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DESCRIPTION JPH04336795

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DESCRIPTION JPH04336795
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
improvement of a bass speaker system.
[0002]
2. Description of the Related Art Conventionally, as a speaker system having an acoustic tube,
those shown in FIGS. 4, 5 and 9 are known. In the figure, 1 is an acoustic tube.
[0003]
As shown in FIG. 4, a speaker unit is attached to one end of the acoustic tube, and the other end
is open. In this case, the side of the speaker unit is regarded as the closed end of the resonance
tube, and the length of the tube is L and the speed of sound in the air is C. Resonance occurs at a
frequency of / 4L (HZ) and its odd multiple, and sound pressure can be efficiently obtained even
in the bass range by appropriately setting the length of L. The sound wave resonating in the
acoustic tube has the highest density on the closed side (unit side) and the lowest density on the
open side, so a small motion of the cone can release large energy and high sound pressure You
can get
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[0004]
Further, the embodiment of FIG. 5 can be regarded as a set of two single-sided closed acoustic
tubes having different lengths bordering a speaker unit, and respective resonance frequencies
can be utilized. The output sound pressure frequency characteristics of the system of FIGS. 4 and
5 are shown in FIGS. In the figure, P1, P2 and P3, P4 are the units shown in FIG. 4 and FIG. 5,
respectively, the sound pressure from the acoustic tube, P shows the synthetic sound pressure,
and the sound pressure from the acoustic tube is for reproduction of the bass range It can be
seen that the effect is exhibited.
[0005]
The example shown in FIG. 9 is, for example, the one disclosed in Japanese Patent Laid-Open No.
2-246699. The basic operation is the same as that shown in FIG. By the enlargement, the tube
resonance frequency can be set low, and unnecessary resonance at f = 3/4 CL (HZ) can be
suppressed to some extent.
[0006]
Also, conventionally, a speaker system having a structure capable of varying the length (volume)
is known.
10 and 11 are, for example, those disclosed in Japanese Patent Laid-Open Nos. 2-41098 and 56795, which do not use the resonance of an acoustic tube as in the present invention, but The
internal volume can be changed by the piston-like slide mechanism and the bellows structure to
change the characteristics of the low range.
[0007]
Although the conventional acoustic tube type speaker system is configured as described above
and is effective for reproduction of the bass region, those shown in FIGS. The frequency of the
sound emitted from is fixed by the length of the tube, for example, if the primary resonance of
the acoustic tube is set to 40 Hz, the length is L = C / 4f = 344/4 × 40 = 2. As it becomes 15 m
and becomes large, there was a problem on movement and installation. In addition, as shown by
the broken line in FIG. 8, the resonance sounds f3, f5, f7... Generated in the higher mode of 3, 5,
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7. There were problems such as interference with the reproduced sound in the high range.
[0008]
Also, although the one shown in FIG. 9 is improved to the reproduction of the bass region, the
point that the resonance frequency is fixed is the same and there is a slight effect on the
reduction of the resonance sound of f3. There is no improvement in the high order peaks above
f4.
[0009]
10 and 11 can change the inner volume, however, in the case of FIG. 10, high-order resonance
generated in the pipe leaks to the outside through the duct, and the one shown in FIG. Since the
entire body of the cabinet is composed of bellows, it is insufficient in strength, and the body itself
resonates at the time of operation or contracts due to internal sound pressure, resulting in an
acoustically undesirable problem.
[0010]
In the conventional speaker using the acoustic tube shown in FIGS. 4 and 5, aluminum, plastic,
laminated paper or the like has been used as the material of the acoustic tube itself.
With metallic materials such as aluminum, the tube itself can maintain its strength, but the
internal loss of the material itself is small, and a long-tailed reverberation and unwanted radiation
have degraded the performance as a speaker.
Further, in the case of an acoustic tube made of plastic or laminated paper, the strength is not
sufficient, and besides the required tube resonance, there are problems such as generation of
abnormal noise due to unnecessary vibration and inability to exhibit sufficient performance.
[0011]
The present invention has been made to solve the above-mentioned problems, and it is an object
of the present invention to obtain an acoustic tube speaker system having excellent performance
and high quality. It is possible to change the structure, suppress generation of high-order mode
resonance sound, and obtain an acoustic tube that is lightweight, rigid and has a large internal
loss.
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[0012]
SUMMARY OF THE INVENTION In order to achieve the above object, the speaker system
according to the present invention can adjust the length of the acoustic tube, and the Helmholtz
resonator can be mounted on the wall of the acoustic tube. The vibration control aluminum alloy
(Al-Si-based or Al-Ni-based alloy) is used as the material of the sound pipe or the acoustic tube.
[0013]
By changing the length of the acoustic tube, the speaker system according to the present
invention not only can appropriately set the frequency of tube resonance, but also is
advantageous for movement and installation.
Then, the Helmholtz resonator provided on the wall surface of the acoustic tube suppresses the
generation of the resonance sound in the unnecessary high-order mode.
In addition, by using a vibration-proof aluminum alloy (Al-Si-based or Al-Ni-based alloy) for the
acoustic pipe, it becomes lightweight, has high rigidity, increases the internal loss of the pipe
itself, and suppresses radiation due to unnecessary vibration.
[0014]
Embodiments of the present invention will now be described with reference to the drawings. In
FIGS. 1, 2 and 3, 1 is an acoustic tube, 2 is a speaker unit, 3 is a variable portion for adjusting the
length of the acoustic tube, and the tube wall comprises a port 4a and an air chamber 4b
following it. A Helmholtz resonator 4 is provided.
[0015]
In FIG. 1, the auxiliary pipe 3a of the same diameter is brought into contact with the acoustic
pipe 1 and screwed to adjust the length of the pipe. In FIG. 2, by making the auxiliary pipe 3b of
different diameter slidable on the acoustic pipe 1, the length of the pipe can be adjusted. In FIG.
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3, the acoustic tube 1 is provided with a bellows 3c, and by expanding and contracting, the
length of the tube can be adjusted, and the tube can be bent halfway.
[0016]
The frequency f of the tube resonance of the characteristics shown in FIG. 6 can be changed
according to the change of the length of the acoustic tube as described above, and the frequency
may be set optimally according to the required acoustic effect. For example, L = C / 4f = 344/4
× 50 = 1.72 m to set to 50 Hz, and L ≒ 1 m to set to 80 Hz. In particular, as shown in FIG. 3 (b),
the system of FIG. 3 can move the position of the exit of the resonance sound as shown in FIG. 3
(b), and the size of the entire system can be reduced to a small scale. Furthermore, the structure
shown in FIGS. 1 to 3 can shorten the overall length during movement of the system, which is
advantageous and allows the overall length of the system to be selected according to the
installation space.
[0017]
Further, as shown in FIGS. 1 to 3, by providing the Helmholtz resonator 4 comprising the port 4a
and the air chamber 4b, high-order resonances shown by broken lines f3, f5,... It is possible to
suppress the generation of sound and generate only the necessary primary resonance sound.
Assuming that the frequency to be suppressed by the Helmholtz resonator is f, the speed of
sound in air is C, the port radius is r, the port length is l, and the air chamber volume is V, the
following equation is established.
[0018]
[Equation 1]
[0019]
Therefore, the shape of the resonator may be set according to the high-order resonance
frequency to be suppressed, and in order to operate in a plurality of modes, a plurality of
resonators may be provided according to each condition.
[0020]
In the above embodiment, an example is shown based on the system in which the acoustic tube is
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provided on one side of the speaker unit as shown in FIG. 4, but the acoustic system is used on
both sides of the speaker unit as shown in FIG. The system having a tube may be used, and the
same effect as that of the above embodiment can be obtained by changing the length of one side
or both sides of the acoustic tube.
[0021]
Next, in FIGS. 4 and 5, the vibration-proof aluminum alloy (Al-Si system or Al-Ni system alloy)
according to the present invention was used for the acoustic tube 1.
[0022]
Next, the composition of each example of the present invention will be shown.
Examples 1 and 2 are Al-Si alloys, and Examples 3 and 4 are Al-Ni alloys.
Further, MM * is misch metal (composition: La 35%, Ce 43%, Na 15%, Pr 4%, Sm 1%, other 2%).
[0023]
[Table 1]
[0024]
Generally, as a mechanism for causing internal friction (damping) in an Al alloy, viscous flow at
the boundaries between second phase particles and matrix, grain boundaries and grain
boundaries, and crystals in dislocations, voids and stacking faults, etc. Absorption of vibrational
energy due to micro defects of
Damping capacity Q-1 represents a scale for converting externally applied vibrational energy into
thermal energy, E represents vibrational energy possessed by the vibration system at the
beginning of one cycle of vibration, and ΔE represents heat during one cycle of vibration. If
energy is converted to energy,
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[0025]
[Equation 2]
[0026]
In the Al-Si alloy of the present invention, when Si is added to Al, Si particles are precipitated in
Al as a matrix to form eutectic crystals.
Then, the interface of the second phase Si particles absorbs the vibration to improve the damping
capacity Q-1.
Fe, Zr, V, Ti and rare earth elements have the function of refining the crystal to increase the grain
boundary, and Na and Sr have the function of refining the Si particle.
Further, when Sn is contained as in the second embodiment, the precipitates are finely
precipitated in the grain boundaries, the viscosity of the grain boundaries is increased, and the
damping ability is improved. The compositions defined in claims 8 and 9 will be described.
[0027]
The Si content is 8 to 20 wt%, preferably 9 to 18 wt%. If it is less than 8 Wt%, sufficient
attenuation ability can not be obtained because less particles are formed. If it exceeds 20 wt%,
the damping ability does not improve because of the formation of coarse Si particles.
[0028]
The content of at least one of Fe, Zr, V and Ti is 0.05 to 0.8 wt%, preferably 0.06 to 0.6 wt%. If it
is less than 0.05 Wt%, the effect of refining the crystal is not sufficient. If it exceeds 0.8 wt%,
coarse metal compounds are formed to impair the damping ability and mechanical properties.
The rare earth element content is 0.05 to 2 wt%, preferably 0.06 to 1.5 wt%. If it is less than 0.05
Wt%, the effect of refining the crystal is not sufficient. On the other hand, if it exceeds 2%, coarse
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metal compounds are formed to impair the damping ability and mechanical properties.
[0029]
One or more of Na and Sr is at most 0.1 wt%, preferably at most 0.05 wt%. If it exceeds 0.1 Wt%,
the miniaturization effect can not be seen. It also impairs the forgery.
[0030]
Sn is 0.005 to 0.1 wt%, preferably 0.008 to 0.08 wt%. If it is less than 0.005 wt%, it is not
sufficient to increase the viscosity of grain boundaries. If it exceeds 0.1 Wt%, the
microsegregation is increased, and the mechanical properties and corrosion resistance are also
degraded without improving the damping capacity.
[0031]
In the Al-Si alloy of the present invention, the average grain size of the second phase particles (Si
particles) needs to be 10 μm or less in the crystal structure, and by setting the average grain
size to 10 μm or less. The interface of the second phase particles can be increased to obtain a
large damping capacity. The average particle diameter is preferably 7 μm or less, more
preferably 5 μm or less.
[0032]
Further, in the Al-Ni alloy of the present invention, when Ni is added to Al, Ni particles are
precipitated in Al as a matrix to form a eutectic structure. The interface of the second phase
Al3Ni particles absorbs vibration to improve the damping capacity Q-1.
[0033]
Further, when Sn is contained as in the fourth embodiment, the precipitates are finely
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precipitated in the grain boundaries, the viscosity of the grain boundaries is increased, and the
damping ability Q-1 is improved. Next, the composition defined in claim 6 and claim 7 will be
described.
[0034]
The Ni content is 4 to 10 Wt%, preferably 4.5 to 8 Wt%. If it is less than 4 Wt%, sufficient
damping ability can not be obtained because less particles are formed. Further, at 10 wt% or
more, due to the formation of coarse particles, the damping ability is not improved and the
mechanical properties are inferior.
[0035]
The content of at least one of Fe, Zr, V and Ti is 0.05 to 0.8 wt%, preferably 0.06 to 0.6 wt%. If it
is less than 0.05 Wt%, the effect of refining the crystal is not sufficient. If it exceeds 0.8 wt%,
coarse metal compounds are formed to impair the damping ability and mechanical properties.
The rare earth element content is 0.05 to 2 wt%, preferably 0.06 to 1.5 wt%. If it is less than 0.05
Wt%, the effect of refining the crystal is not sufficient. Also, if it exceeds 2 Wt%, coarse metal
compounds are formed to impair the damping ability and mechanical properties.
[0036]
Sn is 0.005 to 0.1 wt%, preferably 0.008 to 0.08 wt%. If it is less than 0.005 wt%, it is not
sufficient to increase the viscosity of grain boundaries. If it exceeds 0.1 Wt%, microsegregation is
increased, and the mechanical properties and corrosion resistance are degraded, as well as the
damping ability is not improved.
[0037]
In the Al-Ni alloy of the present invention, the average grain size of the second phase particles
(Al-Ni particles) needs to be 10 μm or less in the crystal structure, and should be 10 μm or less.
Thus, the interface of the second phase particles can be increased, and a large damping capacity
can be obtained. The average particle diameter is preferably 7 μm or less, more preferably 5
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μm or less. Next, examples of the present invention and comparative examples are shown in
comparison.
[0038]
[Table 2]
[0039]
As apparent from the above, the thermal conductivity is superior to that of ordinary purity Al
(99.5 wt%), and the damping ability Q-1 is Al (99 for both the Al-Si alloy and the Al-Ni alloy of the
present invention). One digit larger compared to .5 Wt%, and the elastic modulus and density are
in the same range, so the internal loss can be significantly improved over the conventional
configuration without losing the light weight characteristics and rigidity. It can be seen that the
material is very good.
Recently, Zn-Al based alloys (trade name: Kosmar Z) are noted, but the Al-Si based alloys and AlNi based alloys according to the present invention have larger damping ability, while Zn-Al There
is also a corrosion resistance problem with the base alloys, and the density is nearly doubled,
which is not suitable for weight reduction.
[0040]
In the above embodiment, although the acoustic tube is shown to extend linearly, other shapes
may be used, and the entire acoustic tube may not have the same cross-sectional area, and
similar effects can be expected.
[0041]
Although the above-described example of using the vibration-proof aluminum alloy in FIGS. 4
and 5 has been described, the use of the vibration-proof aluminum alloy in the acoustic tube
shown in FIGS.
[0042]
As described above, according to the present invention, since the length of the acoustic tube can
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be adjusted, the frequency of tube resonance can be changed to change the low range
characteristic of the speaker system. Not only there is an effect that a speaker system having
excellent portability can be obtained, but the Helmholtz resonator can suppress the generation of
unwanted higher-order resonance noise.
Furthermore, according to the present invention, since the damping aluminum alloy is used as
the acoustic pipe, unnecessary reverberation and generation of inherent sound of the pipe itself
can be suppressed, and an acoustic pipe-shaped speaker having excellent performance with less
incidental sound can be obtained. There is.
[0043]
Brief description of the drawings
[0044]
1 is a cross-sectional view of a speaker system for connecting an auxiliary pipe to an acoustic
pipe according to an embodiment of the present invention.
[0045]
2 is a cross-sectional view of a speaker system for connecting a different diameter auxiliary pipe
to an acoustic pipe according to an embodiment of the present invention.
[0046]
3 is a cross-sectional view of a loudspeaker system provided with a bellows according to an
embodiment of the present invention.
[0047]
FIG. 4 is a cross-sectional view of a system in which a speaker unit is attached to one end of an
acoustic tube.
[0048]
FIG. 5 is a cross-sectional view of a system in which a speaker unit is mounted in the middle of an
acoustic tube.
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[0049]
6 is a diagram showing the output sound pressure frequency characteristics of FIG.
[0050]
7 is a diagram showing the output sound pressure frequency characteristics of FIG.
[0051]
FIG. 8 is a graph showing output sound pressure frequency characteristics of the Helmholtz
resonator.
[0052]
9 is a diagram showing an example of the prior art.
[0053]
10 is a diagram showing an example of the prior art.
[0054]
11 is a diagram showing an example of the prior art.
[0055]
Explanation of sign
[0056]
DESCRIPTION OF SYMBOLS 1 sound pipe 2 speaker unit 3a same diameter auxiliary pipe 3b
different diameter auxiliary pipe 3c bellows part 4 Helmholtz type resonance body 4a port 4b air
chamber
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