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DESCRIPTION JP2005294887

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DESCRIPTION JP2005294887
To provide an acoustic system which is large enough to be used in general life, has a well-defined
transient response, and can reproduce reproduced sound faithful to a signal, and yet can
reproduce a bass sufficiently and is simple and inexpensive. To get In a speaker system
comprising a speaker unit and a box forming an air chamber on the back side of the unit, a
breathable acoustic resistance material is present in the vicinity of the back surface of the unit
and there is no air passage other than the acoustic resistance material. It includes a structure in
which the inside of the box is divided into a first air chamber on the diaphragm side of the
speaker unit and a second air chamber on the side farther than the diaphragm of the speaker
unit. [Selected figure] Figure 10
Acoustic system parts and acoustic system
[0001]
The present invention relates to an acoustic system and its parts used when converting an
electrical signal to sound, and further relates to an acoustic system part and an acoustic system
for improving the sound quality of a dynamic speaker system.
[0002]
In conventional acoustic systems, a dynamic speaker unit is often used in which a diaphragm
made of paper or resin is driven by an electromagnetic coil because of its economy and handling.
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1
In this method, a voice coil is disposed in a magnetic field generated by a permanent magnet, and
an acoustic signal current is transmitted to the voice coil to vibrate the diaphragm by the
electromagnetic force generated thereby to vibrate air. The dynamic speaker unit is usually a
baffle plate, an open back box, a closed box, a bass reflex type (phase reversal type) to improve
the reduction of the bass due to the backward sound pressure being opposite to the sound
pressure phase in front of it. ) It is used by attaching to a cabinet called a box etc.
[0003]
The baffle plate or the back opening type box is intended to reduce the influence of the rear
sound pressure by the distance until the sound pressure radiated to the rear of the speaker unit
wraps around the front and prevents the reduction of the front sound pressure. is there. In
addition, the closed type and bass reflex type boxes basically try to prevent the reduction of the
sound pressure by shielding the sound pressure radiated to the rear of the speaker unit from the
surroundings.
[0004]
Generally, the bass reproduction capability of the dynamic type speaker unit depends on the area
of the diaphragm, but this alone is not practical because the diaphragm area is too large to obtain
sufficient bass reproduction capability. Therefore, it is usual to give the resonance characteristics
to the low range by the mass of the vibration system such as the diaphragm, that is, the inertia
and the elasticity such as the edge or damper supporting it, and the electrical impedance of the
coil rises near its resonance frequency fo Because of this, even if the current flowing through the
voice coil is small, the vibration system moves relatively large to compensate for the lack of
sound pressure of the bass. The frequency, sound pressure, and impedance characteristics are
shown in FIG. 1, and the dotted line shows the case where there is no resonance, and the solid
line shows the case where there is resonance and shows the case where it is attached to a box of
sufficient size.
[0005]
Furthermore, when this speaker unit is attached to a finite closed box, the sound pressure
characteristics of the bass are adjusted as necessary by the resonance of the box and the speaker
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unit determined by the air volume in the box. The dashed line shows the characteristic. In this
case, the sound pressure can be obtained sufficiently up to the resonant frequency fr of the box,
but the sound pressure drops sharply if the frequency is lower than that. Patent Document 1 is
intended to control the resonance to improve the sound pressure characteristics of the bass.
Patent Document 1: Japanese Patent Application Laid-Open No. 2002-101494
[0006]
However, these conventional techniques have the following problems.
[0007]
First, if the resonance of the system including the unit and the box is too strong, the transient
response becomes worse and it becomes difficult to faithfully reproduce the original sound
signal.
In general, in a speaker unit with weak resonance, the drive magnetic circuit is set relatively
strong to the inertia (mass) of the vibration system, so that it responds sensitively to small
signals. On the contrary, since the driving magnetic circuit is set relatively weak to the inertia of
the vibration system in the speaker unit having strong resonance, the response to a small signal
tends to be slow. For example, when combining a light-weight car with a strong horsepower
engine, acceleration and deceleration are both quick, but conversely, when a heavy-weight car is
combined with a weak engine, acceleration and deceleration become slow.
[0008]
Therefore, the response to a weak signal is better if the resonance is weak. However, if the
resonance is weak, the amplitude of the vibration system is insufficient near the resonance
frequency, and the sound pressure is insufficient. In particular, in a small-aperture speaker unit,
in order to keep the sound pressure in the space at the same level as the bass and the treble, it is
necessary to vibrate with a larger amplitude in the bass and it becomes painful.
[0009]
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The sound pressure and impedance characteristics when the speaker unit is attached to the box
are as shown in FIG. In FIG. 2, the solid line indicates that resonance is strong, and the dotted line
indicates that resonance is weak.
[0010]
Next, when the speaker unit is attached to a baffle plate or a rear open box, the degree of
attenuation of the bass changes depending on the path length where the sound pressure wraps
around from the rear to the front of the speaker unit, but the path length is finite. There is no
excuse for the decrease in sound pressure.
[0011]
Furthermore, when the speaker unit is attached to a closed box or bass reflex type box, if the
internal volume of the box is small, as described above, the resonance frequency of the system
becomes high, and a bass up to the necessary bass range can not be obtained.
[0012]
In addition, if the sound absorption processing inside the box is insufficient, a standing wave
occurs inside at a specific frequency, and unintended vibration occurs in the diaphragm of the
speaker due to the back sound pressure due to the standing wave, so that the original sound
signal can be faithfully reproduced It becomes difficult.
Moreover, it is considered that the electric impedance is high in the frequency band where the
resonance occurs, and the electric driving force to the vibration system is weak, so that it is likely
to be affected.
If the electric driving force is strong, including the case where the internal resistance of the
amplifier for driving the speaker is very small, it is possible to drive the diaphragm sufficiently
intended against the back surface sound pressure in the resonance frequency band. It should be
possible.
[0013]
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In addition, it is also a factor that in general glass wool and other fibrous sound absorbing
materials, the sound absorbing effect at low frequencies is low and sufficient sound absorbing
effect can not be obtained in the resonance frequency band of a speaker or a box. On the
contrary, when the sound absorption processing becomes excessive, resonance becomes
insufficient and the sound becomes insufficient.
[0014]
As described above, in the speaker system using the conventional dynamic type speaker, there is
a difference in response to a minute signal due to the influence of the resonance of the speaker
unit and the box against the problem of faithful reproduction of the original sound signal.
Vibration not found in the original sound occurs due to the effect of back sound pressure due to
box resonance to the back surface or standing wave, and the vibration of the diaphragm faithful
to the original sound can not be made. Conversely, the vibration of the diaphragm was vibrated
faithfully to the electric signal In the case, there was a contradictory issue that the sound
pressure in the low range was insufficient.
[0015]
On the other hand, there is also a speaker system called horn type speaker system which does
not actively utilize resonance.
This vibrates a lightweight diaphragm with a voice coil and guides the air flow generated by the
vibration in front of the diaphragm to a suitable narrow space acting as an acoustic transformer,
and a horn with large acoustic resistance in front of it. To obtain sufficient sound pressure. In
this case, the degree of resonance is made as small as possible in order to widen the reproduction
frequency band. Therefore, this speaker system is generally known as a system with high clarity
of reproduction and good transient response.
[0016]
However, if it is going to reproduce sufficient low sound with this system, it is necessary to make
the opening of the horn considerably large, and it is difficult to make it large enough to be used
casually in ordinary life. Therefore, the object of the present invention is to make a sound system
which is large enough to be used in general life, has a clear transient response, and can
reproduce reproduced signals faithful to the signal, and yet can reproduce bass well. It aims at
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obtaining cheaply with a common structure.
[0017]
Therefore, according to the first aspect of the present invention, there is provided a speaker
system comprising a speaker unit and a cabinet separating an air layer by a front portion and a
back portion of the unit. In addition, by covering so that there is no air passage, a first air
chamber is formed on the back of the diaphragm of the speaker unit to separate the air layer on
the side farther than the diaphragm of the speaker unit from the first air chamber. A part for an
acoustic system characterized by being arranged in
[0018]
According to a second aspect of the present invention, there is provided a speaker system
comprising a speaker unit and a box forming an air chamber on the back side of the unit, an airpassing acoustic resistance material in the vicinity of the back surface of the unit And the
speaker system having a structure in which the inside of the box is divided into a first air
chamber on the diaphragm side of the speaker unit and a second air chamber on the side farther
than the diaphragm of the speaker unit. It provides an acoustic system.
[0019]
According to the third aspect of the present invention, there is provided an acoustic system using
the parts for acoustic system according to the first aspect or the acoustic system according to the
second aspect provided with a bass amplifier circuit.
[0020]
In general, it is known that breathable porous materials have an acoustic resistance.
It is believed that the friction between the air particles occurs as the air flow passes through a
large number of small holes in the material.
[0021]
In the first aspect of the invention, the inventor considered covering the vicinity of the rear of the
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diaphragm of the cone-shaped dynamic speaker unit with the air-permeable porous material to
reduce the degree of resonance of the unit.
In this case, the volume of the first air chamber on the rear surface of the diaphragm of the
speaker unit is small, and the air flow from the first air chamber due to the density of air
generated in the air chamber on the rear side due to the vibration of the speaker diaphragm
Since all the exchange takes place only through the small holes of the acoustic resistance
material, the acoustic load (resistance) of the diaphragm is increased, excessive vibration at
resonance to the electric drive signal of the diaphragm of the speaker unit is suppressed, and
resonance phenomenon Is effective.
[0022]
This approximates to the relationship between the solid line and the dotted line in FIG. 2, and the
solid line corresponds to the case where the acoustic resistance material of claim 1 does not
exist, and the dotted line corresponds to the case where the acoustic resistance material exists.
[0023]
By using the acoustic resistance material according to claim 1, excessive vibration due to the
resonance of the diaphragm of the speaker unit is suppressed and the fidelity of the vibration of
the diaphragm to the signal is increased, so the transient response is improved and the sound
quality is clear. become.
In addition, since the air flow is not completely shut off because there is adequate air
permeability, the vibration of the diaphragm at low frequencies is not suppressed at all, and the
diaphragm drives the voice coil even at low frequencies. The force can be suitably vibrated and
the air pressure is reduced accordingly when the air flow comes out of the acoustically resistant
material to the outer air layer.
It is considered that this is because the energy flow due to the friction of air particles due to the
air flow passing through the small holes in the acoustically resistant material and the vibration of
the acoustically resistant material itself occurs.
[0024]
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Therefore, in this case, the sound pressure in the reverse phase of the back surface of the
diaphragm is weakened in the low frequency range compared to when the speaker unit is
electrically driven in the naked state, so the sound pressure returns in front of the speaker unit.
Can be increased. That is, the invention of claim 1 can provide parts for an acoustic system
having these effects.
[0025]
Next, according to the second aspect of the invention, in the speaker system comprising the
speaker unit and a box forming an air chamber on the back side of the unit, a sound resistance
material having air permeability in the vicinity of the back surface of the unit is used. Including a
speaker system that is covered so that there is no air passage, and the inside of the box is divided
into a first air chamber on the diaphragm side of the speaker unit and a second air chamber on
the side farther than the diaphragm of the speaker unit An acoustic system was provided.
[0026]
According to this structure, the speaker unit can reduce the degree of resonance as in claim 1,
and the back surface sound pressure of the diaphragm due to the resonance of the second air
chamber in the box vibrates the speaker unit through the acoustic resistance material. It will
reach the board and its effect can be made smaller by the presence of the acoustically resistant
material.
[0027]
Therefore, as indicated by the solid line in FIG. 1, the resonance frequency is less likely to be
pulled higher by the resonance frequency of the second air chamber in the box as shown by the
alternate long and short dash line. .
Furthermore, the back sound pressure influence on the diaphragm by the standing wave of the
second air chamber of the box can be weakened by the presence of the acoustic resistance
material, and vibration excitation other than the vibration of the diaphragm by the drive signal to
the voice coil Can be weakened, so that the diaphragm vibrates faithfully to the drive signal.
[0028]
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Thus, according to the invention of claim 2, when the speaker unit is attached to the box, it is
possible to provide a speaker system in which the diaphragm vibrates faithfully to the drive
signal applied to the voice coil of the speaker unit. Thus, it is possible to provide an acoustic
system in which the transient response of the reproduced sound is increased and the clarity of
the reproduced sound is improved.
[0029]
The invention of claim 3 provides an acoustic system using the parts for acoustic system of claim
1 or the acoustic system of claim 2 provided with a bass amplifier circuit.
As described in the effects of the invention of claim 1 and claim 2, by using the parts for acoustic
system and the acoustic system, the vibration of the diaphragm of the speaker unit has an effect
of faithfully vibrating by the source signal, The sound pressure of the bass is reduced as shown
by the dotted line in FIG. 2 compared to the source signal, and it can not be said that the sound
pressure including the sound pressure is faithful.
[0030]
Therefore, by adding to the system a bass enhancement circuit that compensates for the drop in
bass sound pressure, it is possible to obtain an acoustic system capable of almost faithful original
sound reproduction.
[0031]
FIG. 3 shows the situation.
In the figure, the solid line indicates the frequency sound pressure characteristics using the parts
for sound system of claim 1 or the sound system of claim 2, but the sound pressure decreases as
the frequency decreases.
Therefore, by adding an electric circuit having a low-pass amplification characteristic as shown
by a dotted line to the system, it is possible to improve the frequency to sound pressure
characteristic as shown by a dot-and-dash line.
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[0032]
In this case, the vibration of the diaphragm of the speaker unit according to claims 1 and 2 is
true to the source signal, and the transient response is also well-defined. While maintaining the
sound pressure, the transient response is good and a faithful reproduced sound can be obtained.
In addition, the means of claims 1 to 3 is very simple and inexpensive because only the addition
of an acoustic resistance material or the addition of a bass amplifier circuit to the conventional
structure is required.
[0033]
FIG. 4 shows an embodiment of claim 1 of the present invention. In the figure, reference numeral
101 denotes a ring-shaped acoustic resistance material made of a porous material having air
permeability, and is formed of, for example, a sponge-like material such as urethane foam.
Reference numeral 102 denotes a plate-like acoustic resistance material formed of an acoustic
resistance material similar to 101. The surfaces 1012 and 102 of 101 are adhered with an
adhesive, double-sided tape or the like as shown in 1 of FIG. 5, and a concave portion is formed
on the inner surface so as to wrap the rear surface shape of the speaker unit. Further, the
acoustic resistance material 1 of FIG. 5 may not be a combination of two shapes as shown in FIG.
4, but may be integrally formed in advance by a mold or the like.
[0034]
The acoustic resistance material 1 of FIG. 5 is used as shown in FIG. In FIG. 6, 2 is a speaker unit
and 3 is a baffle plate. The speaker unit is attached to the opening 301 of the baffle plate 3 from
its front surface with a screw or the like. The front surface portion 1011 of the acoustic
resistance material 1 is attached to the back surface of the baffle plate 3 with an adhesive or a
double-sided tape. The reference numeral 4 denotes a lead wire for electrically drawing out the
voice coil terminal of the speaker unit, which leads from the inside of the acoustic resistance
material 1 to the outside without impairing the confidentiality.
[0035]
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Due to this structure, a small space (first air chamber) 5 where air can not pass through other
than the acoustic resistance material 1 is generated on the back side of the diaphragm 201 of the
speaker unit 2, and the resonance characteristic of the speaker unit 2 is the above-mentioned
claim As described in the effect of the first invention, the solid line to the dotted line in FIG. 2 can
be used. Further, in the first air chamber 5, the wall surface in the first air chamber is a sound
resistance material having small holes, so it has a sound absorbing effect, and if it is a material
having elasticity such as urethane foam, the wall surface itself is Because it is soft, there is almost
no occurrence of standing waves. The degree of characteristic change from the solid line to the
dotted line in FIG. 2 can be adjusted by the foaming degree, thickness, etc. of the acoustic
resistance substance 1.
[0036]
FIG. 7 shows an example in which the acoustic resistance material 1 is bonded to a ring-shaped
frame 6 fixed between the baffle plate 3 and the speaker unit 2 according to the second
embodiment of the invention of claim 1, and FIG. An example in which the frame 6 is fixed to the
back surface of the baffle plate 3 and FIG. 9 is an example in which an acoustic resistance
material is bonded so as to cover the opening 202 of the frame of the speaker unit 2. The first air
chamber 5 or 7 is formed.
[0037]
FIG. 10 is a cross-sectional view of a speaker system in which the speaker unit 2 and the acoustic
resistance material 1 are attached to the closed box 8 according to the second embodiment of the
present invention.
In FIG. 10, the speaker unit 2, the baffle portion 801, the acoustic resistance material 1, and the
first air chamber 5 are the same as those shown in FIG. In FIG. 10, 9 is a second air chamber, and
10 is a sound absorbing material.
[0038]
In this way, an acoustic system is obtained in which the effect described in the above-mentioned
invention of claim 2 is obtained by dividing the inside of the box 8 into the first air chamber 5
and the second air chamber 9 with the acoustic resistance substance 1 in this way. You can get it.
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[0039]
FIG. 11 shows an embodiment in which the box is of the open back type, and FIG. 12 is an
embodiment in which the box reflex is of the bass reflex type (phase inversion type).
11, 11 in FIG. 12, and 9 in FIG. 12 correspond to the second air chamber, but any effect that the
acoustic resistance material 1 reduces the vibrational influence of the resonance or the standing
wave on the diaphragm of the speaker unit 2 is. It is similar to the case of FIG.
[0040]
In the embodiment of FIG. 12, reference numeral 12 denotes a resonance port called a duct, but
the effect is that the frequency is slightly different from the resonance of the second air chamber,
and the diaphragm of the speaker unit by the second air chamber is It has nothing to do with the
influence of
[0041]
FIG. 13 shows a first embodiment of the invention shown in claim 3. In FIG.
In FIG. 13, reference numeral 13 is an electric signal of a sound source, 14 is an amplifier, for
example, a preamplifier, 15 is a bass amplifier circuit, 16 is a power amplifier for driving a
speaker, and 17 is a speaker system similar to FIG.
[0042]
The bass amplifier circuit 15 of FIG. 13 may be, for example, a circuit using CR as shown in FIG.
The circuit of FIG. 14 constitutes a treble attenuation circuit having a first cutoff characteristic
with R1 and C1, and a bass boost circuit having a second cutoff characteristic with R2 and C1.
The attenuation characteristic is shown in FIG. As such, it has a characteristic that it attenuates at
6 dB / oct from the first cutoff frequency fcL to the second cutoff frequency fcH. An amplifier
(AMP) may be provided as shown in FIG. 14 as necessary.
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[0043]
In the sound system in which the bass amplifier circuit 15 is added as shown in FIG. 13, the
frequency-sound pressure characteristics (solid line in FIG. 3) of the seventeen speaker systems
are comprehensively selected by appropriately selecting fcH in FIG. An improved characteristic
can be obtained as indicated by an alternate long and short dash line.
[0044]
It is also possible to use such a bass amplifier circuit in two stages as shown in FIG.
In general, the frequency sound pressure characteristics of the speaker system shown in FIG. 10
are as shown in FIG. That is, the sound pressure drop of the bass starts from the bass bend point
fc1 of the speaker unit, and the frequency drops further, and the sound pressure further drops
from the bass bend point fc2 due to the influence of the box volume.
[0045]
Therefore, by using two stages of bass amplifier circuits having different characteristics as shown
in FIG. 16 in combination, it is possible to eliminate the lack of sound pressure of bass below the
bass curve fc2 as well. Furthermore, if the bass amplifier circuits of FIG. 13 and FIG. 16 are used,
the effect of compensating the frequency-phase characteristics of the speaker system 17 of FIG.
13 and FIG. 16 to some extent can be expected.
[0046]
That is, it is known that the frequency-phase characteristic of the speaker system is generally as
shown in FIG. That is, as the frequency decreases from the bass bending point fc1 of the speaker
unit, the phase gradually advances with respect to the signal of the sound source, and becomes
about 90 degrees in phase lead at the resonance frequency fr as the system. When the frequency
is further lowered, the sound pressure is lowered due to the restriction of the capacity of the box,
and the phase lead is increased to generate the phase lead of up to 180 degrees.
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[0047]
However, the frequency-phase characteristic of the bass amplifier circuit of FIG. 14 can be made
to have a phase delay near 90 degrees at maximum around fr by selecting fcL and fcH
appropriately as shown in FIG. The phase characteristic of fr can be corrected. In addition, using
two stages of the bass amplifier circuit as shown in FIG. 16 adds another phase delay, so that it is
possible to compensate for the phase shift near the maximum of 180 degrees in FIG. FIG. 20
shows phase compensation characteristics in the case of two stages.
[0048]
According to the present invention, in an audio apparatus in which pure and faithful
reproduction sound is required for a sound source signal, not only a speaker system that covers
the entire band with one speaker but also a 2-way or 3-way or multi-amplifier system The
present invention can be applied to pure audio systems, as well as to audio systems requiring
high quality sound in home appliances using dynamic speakers such as audio visuals, TVs,
personal computers and portable radio / tape recorders.
[0049]
Diagram showing the frequency sound pressure and frequency impedance characteristics of the
dynamic speaker system Figure 2 shows the improvement of the frequency sound pressure
characteristics of the dynamic speaker system in the diagram showing the frequency sound
pressure and frequency impedance characteristics of the dynamic speaker system Diagram of the
configuration of parts for acoustic system according to claim 1 Diagram of parts for acoustic
system according to claim 1 of the present invention Diagram of use example of parts for
acoustic system according to claim 1 of the present invention acoustic system according to claim
1 of the present invention Figure of another embodiment of the part for a picture Diagram of
another example of the part for an acoustic system according to the invention 1 claim 1 Figure of
another embodiment of a part for an acoustic system according to the claim 1 of the invention
claim of the invention Diagram of acoustic system according to claim 2 Diagram of another
embodiment of acoustic system according to claim 2 of the present invention Claim of the
present invention Figure of another embodiment of the sound system according to the invention
Figure of the sound system according to claim 2 of the invention Example of a bass amplifier
circuit Figure of the characteristics of the circuit of Figure 14 Another embodiment of the sound
system according to claim 2 of the invention Diagram of characteristic of speaker system
Diagram of characteristic of speaker system Diagram of phase characteristic of bass amplifier
circuit Diagram of phase characteristic of bass amplifier circuit
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Explanation of sign
[0050]
1 и и и Parts for sound system 2 и и Speaker unit 3 и и Baffle plate 4 и и Lead wire 5 и и First air
chamber 6 и и Frame 7 и и First air chamber 8 и Box 9 и и и Second air chamber 10 иии Sound
absorbing material 11 и и и Second air chamber 12 и и Second air chamber 13 и и Signal source 14 и и
Amplifier 15 и и Bass amplifier circuit 16 и и Amplifier 17 и и Speaker system
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