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DESCRIPTION JP2007060501

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DESCRIPTION JP2007060501
An internal space of a sealed cabinet is filled with a gas having a specific heat ratio smaller than
that of carbon dioxide gas when at least one or more speaker units are attached to the cabinet.
SOLUTION: In a cabinet 12 in which at least one or more speaker units 11 are attached to at least
one surface 12a and an inner space is sealed, a gas 13 with a specific heat ratio of 1.28 or less is
filled. An acoustic converter 10 is provided. [Selected figure] Figure 1
Electro-acoustic transducer
[0001]
The present invention radiates sound waves at a low frequency by filling a gas having a specific
heat ratio of 1.28 or less in a cabinet in which at least one or more speaker units are attached to
at least one surface and the internal space is sealed. The present invention relates to an
electroacoustic transducer that can increase the efficiency.
[0002]
In general, a speaker unit for emitting a sound wave includes a diaphragm, a voice coil fixed to
the diaphragm, and a magnetic circuit having a magnet for applying a magnetic field to the voice
coil. When an audio signal voltage is applied to the voice coil installed in the motor, current flows
and the diaphragm is driven by the electromagnetic force to generate a sound wave which is a
compressional wave of air on the front of the diaphragm. A cabinet is used for the purpose of
shielding the front and the back so that the back and forth waves are generated, but the front
and back are not canceled so that the internal space on the back side of the diaphragm is Sealing
has the advantage that the shielding effect can be obtained down to low frequencies.
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[0003]
Under the present circumstances, there exist some with which the interior space of the cabinet
which attached the speaker unit was filled with the carbon dioxide gas (patent document 1).
JP-A-4-117900
[0004]
FIG. 3 is a longitudinal sectional view showing a conventional speaker system.
[0005]
The conventional speaker system 100 shown in FIG. 3 is disclosed in the above-mentioned Patent
Document 1 (Japanese Patent Application Laid-Open No. 4-117900), and will be briefly
described with reference to Patent Document 1 here.
[0006]
As shown in FIG. 3, in a conventional speaker system (electro-acoustic transducer) 100, a coneshaped speaker unit 101 as a speaker unit is mounted in a mounting hole 102a1 drilled on one
side (front) 102a of a closed cabinet 102. Is attached to
[0007]
Furthermore, the internal space of the closed cabinet 102 is filled with carbon dioxide gas (CO 2)
103 as a gas (gas) whose product of the second power of sound velocity and density is smaller
than that of air.
[0008]
At this time, since the lowest resonance frequency f0 of the cone-shaped speaker unit 101
depends on the carbon dioxide gas 103, it can be lowered compared to the case of air alone,
whereby good sound wave emission is performed at a low frequency. It is disclosed that excellent
frequency characteristics can be obtained.
[0009]
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By the way, in the conventional speaker system 100, as described above, the lowest resonance
frequency f0 of the cone-type speaker unit 101 is lowered by filling the internal space of the
cabinet 102 to which the cone-type speaker unit 101 is attached with the carbon dioxide gas
103. Recently, with the increase in size of displays and the increase in density of optical
recording media, etc., it is necessary to obtain further superior frequency characteristics to the
speaker system, and this requirement is required in the conventional speaker system 100. No
sufficient measures have been taken against the problem, and the reason will be described below
with reference to FIG.
[0010]
FIG. 4 is a diagram showing frequency characteristics with respect to the volume of the cabinet in
which the speaker unit is attached.
[0011]
Generally, when the speaker unit is attached to one surface of the cabinet and the internal space
of the cabinet is sealed, the air in the internal space of the cabinet is compressed or expanded
when the diaphragm of the speaker unit vibrates, so the atmospheric pressure There is a
pressure difference between the two, which causes a reaction on the diaphragm and prevents
movement of the diaphragm.
[0012]
Here, the smaller the volume of the interior space of the cabinet, the greater the change in
pressure and consequently the greater the degree of interference.
That is, as shown in FIG. 4, when the cabinet volume is large, the cabinet volume is medium, and
the cabinet volume is small, the minimum resonance frequency f0 increases as the cabinet
volume decreases. As the resonance sharpness Q also increases, the efficiency below the lowest
resonance frequency f0 decreases.
[0013]
Under the present circumstances, when the grade of the reaction by the internal / external
pressure difference seen from the diaphragm is represented by spring constant k, a following
formula (1) is materialized.
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[0014]
Incidentally, the volume modulus K of the gas in the cabinet shown in the equation (1) is the
following equation (where the volume V of the inner space of the cabinet is deformed by Δv
under the uniform pressure p): 2) holds.
[0015]
Then, according to the above equation (1), in order to reduce the spring constant k and reduce
the influence of the reaction, increase the volume V of the internal space of the cabinet or reduce
the effective area S of the diaphragm Or, it is sufficient to reduce the bulk modulus K of the
internal space of the cabinet, but increasing the volume V of the internal space of the cabinet
contradicts with the downsizing of the speaker system, and the effective area S of the diaphragm
is If it is smaller, there is a drawback that the stroke for obtaining the necessary sound pressure
is increased.
[0016]
Therefore, it is sufficient to reduce the bulk modulus K of the gas in the cabinet.
Under the present circumstances, since compression and expansion of the internal gas in an
audio | voice frequency are considered to be an adiabatic process, the volume elastic modulus K
of the gas in a cabinet can also be represented like a following formula (3).
[0017]
The specific heat ratio γ of the above-mentioned gas is the ratio between the constant pressure
heat capacity and the constant volume heat capacity, and what is used for the analysis of
thermodynamics is the constant pressure heat capacity (constant pressure specific heat) and
constant heat capacity (constant volume heat capacity per constant). Ratio to specific heat).
[0018]
At this time, the specific heat capacity of the gas and the specific heat ratio are determined by the
structure of the molecule, in other words, determined by the type of gas, and in Table 1 below,
the constant pressure / constant volume specific heat capacity and specific heat of each gas at
25 ° C. An example of the ratio is shown.
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[0019]
At this time, when air is contained in the internal space of the cabinet, the specific heat ratio of
the air is 1.40, which is the same as oxygen (O 2) shown in Table 1, while on the other hand, the
inside of the cabinet as described in the conventional example. The specific heat ratio of carbon
dioxide gas (CO <2>) is 1.29 when the space is filled with carbon dioxide gas (CO <2>), which
also indicates that carbon dioxide gas having a specific heat ratio smaller than that of air. It can
be seen that better frequency characteristics can be obtained if the gas (CO <2>) is filled, but if
the specific heat ratio of the gas can be further smaller than the carbon dioxide gas (CO <2>), it is
more excellent. It is clear that frequency characteristics can be obtained.
[0020]
Therefore, an electro-acoustic transducer is desired in which when the at least one speaker unit
is attached to the cabinet, the internal space of the sealed cabinet is filled with a gas having a
smaller specific heat ratio than carbon dioxide gas.
[0021]
The present invention has been made in view of the above problems, and the invention according
to claim 1 has a specific heat ratio of 1 in a cabinet in which at least one or more speaker units
are attached to at least one surface to seal an internal space. It is an electroacoustic transducer
characterized by being filled with a gas of .28 or less.
[0022]
The invention according to claim 2 is the electro-acoustic transducer according to claim 1,
wherein the gas contains HFCs (hydrofluorocarbons) or HCFCs (hydrochlorofluorocarbons). It is a
converter.
[0023]
According to the electro-acoustic transducer according to claim 1, by filling at least one or more
speaker units on at least one surface and filling a gas with a specific heat ratio of 1.28 or less in a
cabinet in which the internal space is sealed. The radiation efficiency of the sound wave at a low
frequency can be enhanced, and the sound wave radiation can be better at a lower frequency
than in the conventional example filled with carbon dioxide gas, and a more excellent frequency
characteristic can be obtained.
[0024]
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Further, according to the electro-acoustic transducer of claim 2, when HFCs (hydrofluorocarbons)
or HCFCs (hydrochlorofluorocarbons) are used as the gas having a specific heat ratio of 1.28 or
less, these gases may be used. Are commercially available, and the electroacoustic transducer 10
can be provided inexpensively.
[0025]
An embodiment of an electroacoustic transducer according to the present invention will be
described in detail with reference to FIGS. 1 and 2.
[0026]
FIG. 1 is a longitudinal sectional view showing an electro-acoustic transducer according to the
present invention, and FIG. 2 is a comparative example in the case where air is filled in a cabinet
and in an example where an cabinet is filled with HFC-134a. Is a diagram showing frequency
characteristics of
[0027]
As shown in FIG. 1, in the electro-acoustic transducer (speaker system) 10 according to the
present invention, the speaker unit 11 is mounted in a mounting hole 12a1 formed in the front
surface 12a of the closed cabinet 12.
[0028]
In this embodiment, a single speaker unit 11 is shown attached to the cabinet 12. However, the
present invention is not limited to this. For example, a plurality of speaker units 11 for the low
frequency range, high frequency range, etc. In other words, at least one or more speaker units 11
are attached to at least one surface of the closed cabinet 12.
[0029]
The above-described speaker unit 11 uses a cone type frame 11a attached in a mounting hole
12a1 formed in the front surface 12a of the closed cabinet 12 and a soft rubber material at the
front edge of the frame 11a. Edge member 11b bonded together, a diaphragm 11c vibratably
supported in the frame 11a with the front edge bonded to the edge member 11b, and a voice coil
11d fixed to the rear end of the diaphragm 11c. When a voice signal voltage is applied to the
voice coil 11d installed in the magnetic circuit 11e, a magnetic circuit 11e is provided with a
magnet for vibrating the diaphragm 11c and the voice coil 11d integrally, and a current flows,
causing an electromagnetic force Drive the diaphragm 11c to generate a sound wave which is a
compressional wave of air on the front surface of the diaphragm 11c, Coherence waves of the
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front and back are generated on the back of the diaphragm 11c, but the cabinet 12 seals the
internal space on the back side of the diaphragm 11c so that the compression and compression
waves on the front are not canceled. Shielding effect can be obtained up to the frequency.
[0030]
Here, in this embodiment, in order to lower the lowest resonance frequency f0 of the speaker
unit 11, a specific heat ratio of 1.28 or less smaller than a specific heat ratio of 1.29 of carbon
dioxide gas (CO2) in the internal space of the sealed cabinet 12 And containing HFCs
(hydrofluorocarbons) or HCFCs (hydrochlorofluorocarbons) consisting of molecules of 3 atoms or
more as a gas satisfying the condition of a specific heat ratio of 1.28 or less. doing.
[0031]
At this time, as the specific heat ratio of the gas becomes smaller according to the equation (3),
the bulk modulus K of the gas in the cabinet 12 can be set smaller, and the specific heat ratio of
the gas is preferably 1.20 or less.
[0032]
More specifically, for example, HFC-134a (1,1,1,2-tetrafluoroethane) having a specific heat ratio
of 1.1186 is used as the HFCs (hydrofluorocarbons), or HCFCs (hydro As chlorofluorocarbons,
for example, R-22 (chlorodifluoromethane) having a specific heat ratio of 1.185 is used.
[0033]
Furthermore, as a gas other than the above, R-410A (HFC-32 / HFC-125... 50/50 wt%) having a
specific heat of 1.175 or R-407C (HFC-32 / HFC) having a specific heat of 1.144 23/25/52 wt%),
R-404A (HFC-143a / HFC-125 / HFC-134a ... 52/44/4 wt%) with a specific heat of 1.1118 A
mixture of HFCs such as R-507A (HFC-143a / HFC-125... 50/50 wt%) which is 1.117 may be
used.
[0034]
At this time, the filling amount of HFCs (hydrofluorocarbons) or HCFCs
(hydrochlorofluorocarbons), which is superior to carbon dioxide gas, may be 40% or more by
volume ratio, but the filling amount is high if the amount is high. The bass characteristics are
better obtained.
[0035]
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Here, as a comparative example to this embodiment, the case where air with a specific heat ratio
of 1.40 is filled with a volume ratio of 100% in the cabinet 12 and the HFC with a specific heat
ratio of 1.1186 in the cabinet 12 as an embodiment Compared with the case where the volume
ratio of -134a is 100%, HFC-134a can reduce the volume modulus K to 1.1186 / 1.4 = 0.80 times
compared to the case of air. Therefore, this can lower the lowest resonance frequency f0 by
about 11%, and can improve the efficiency of the low band by about 2 dB.
[0036]
And the result of having calculated the frequency characteristic by an above-mentioned
comparative example and an above-mentioned example is shown in FIG.
As apparent from FIG. 2, the frequency characteristics better than the comparative example are
obtained in the example.
[0037]
In the prior art described above, since the cabinet is filled with carbon dioxide gas having a
specific heat ratio of 1.29, the frequency characteristic when this carbon dioxide gas is used is
not shown in FIG. Needless to say, although it is superior to the comparative example, it is lower
than the present example.
[0038]
Furthermore, although not shown here, in the bass reflex type electroacoustic transducer in
which a cylindrical port for resonating air is formed on at least one surface of the cabinet to
which the speaker unit is attached, the cylindrical port is also provided. A vibratable movable
partition using a soft membrane that does not transmit gas molecules is attached to the inlet,
middle, or outlet of the case to seal the inside of the cabinet, and the specific heat ratio is smaller
in this cabinet than carbon dioxide gas It is also possible to fill and configure.
[0039]
As described above in detail, according to the electroacoustic transducer pertaining to the
present invention, a specific heat ratio is 1.28 or less in a cabinet in which at least one speaker
unit is attached to at least one surface to seal an internal space. By filling the gas, the radiation
efficiency of the sound wave at a low frequency can be enhanced, and the sound wave emission
is better at a lower frequency than the conventional example filled with a carbon dioxide gas, and
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a more excellent frequency characteristic is obtained. Be
[0040]
In addition, when HFCs (hydrofluorocarbons) or HCFCs (hydrochlorofluorocarbons) are used as
the gas having a specific heat ratio of 1.28 or less, these gases are commercially available, so the
electroacoustic transducer 10 is used. It can be provided inexpensively.
[0041]
FIG. 1 is a longitudinal sectional view showing an electro-acoustic transducer according to the
present invention.
It is the figure which showed each frequency characteristic when the case where air is filled in a
cabinet as a comparative example, and when filling a cabinet inside as an Example HFC-134a.
It is the longitudinal cross-sectional view which showed the conventional speaker system.
It is a figure showing the frequency characteristic to the volume of the cabinet which attached
the speaker unit.
Explanation of sign
[0042]
DESCRIPTION OF SYMBOLS 10 ... Electro-acoustic conversion apparatus, 11 ... Speaker unit, 11a
... Frame, 11b ... Edge member, 11c ... Diaphragm, 11d ... Voice coil, 11e ... Magnetic circuit, 12 ...
Cabinet, 12a ... Front surface, 12a1 ... Mounting hole, 13 ... Gas with a specific heat ratio of 1.28
or less.
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