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JPH0998495

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DESCRIPTION JPH0998495
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo speaker apparatus for reproducing a two-channel stereo signal. Specifically, the speaker
apparatus for the left channel and the right channel has directivity obtained by the combination
of the directivity and the omnidirectionality, and the speaker for sound reproduction of the
speaker apparatus for the left channel and the right channel is The present invention relates to a
stereo speaker apparatus capable of expanding a listening range in which a good stereo feeling
can be obtained with a relatively compact system configuration by attaching to a speaker box so
that the main axis is directed inward.
[0002]
2. Description of the Related Art FIG. 15 shows a state where a conventional stereo speaker
device is disposed in a trial listening room 100. As shown in FIG. This speaker device comprises a
left channel speaker device 1L having an audio signal reproducing speaker for reproducing a left
channel audio signal, and a right channel speaker device 1R having an audio signal reproducing
speaker for reproducing a right channel audio signal. It is done.
[0003]
According to such a speaker device, basically, correct sound image localization is obtained
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between the speaker devices 1L and 1R at a listening position on the center line M of the speaker
devices 1L and 1R, for example, at a point The original sound stage of 2-channel stereo is
reproduced. However, at a listening position deviated from the center line M, for example, at
point b, sound image localization shifted to the direction of the speaker device 1R due to a
difference in the distance attenuation of the sound wave, etc. does not occur, and the original
sound stage as 2-channel stereo is not reproduced .
[0004]
That is, in FIG. 15, when the sound signal reproduction speakers of the speaker devices 1L and
1R are driven by the same signal, the sound image at the listening position on the center line M
of the speaker devices 1L and 1R, for example, a point a is indicated by arrows. Localize in front
of the center. Therefore, when a normal stereo signal is reproduced, a continuous sound stage is
reproduced between the speaker devices 1L and 1R (shown by a dashed-dotted line La).
[0005]
Here, with regard to sound localization of two-channel stereo sound, the following properties are
known in terms of hearing. The sound image at the listening position on the center line M of the
speaker devices 1L and 1R, for example, the sound image at point a moves in the direction of the
speaker device having a high sound pressure level if there is a level difference in sound pressure
of sound waves from the speaker devices 1L and 1R. Do. If a delay time of 1 to 30 ms is given to
any of the signals for driving the sound signal reproducing speakers of the speaker devices 1L
and 1R, the listening position on the center line M of the speaker devices 1L and 1R, for example,
a point The sound image moves in the direction of the loudspeakers where the sound waves
arrive earlier in time. This phenomenon is called leading effect and is well known.
[0006]
In consideration of such a characteristic of hearing, let us consider sound image localization at a
listening position, for example, point b off the center line M of the speaker devices 1L and 1R.
Since the distance between the sound receiving point and the speaker devices 1L and 1R is
different at this point b, when the directivity of the speaker devices 1L and 1R is omnidirectional,
the arrival time difference occurs in the sound waves from the speaker devices 1L and 1R.
Pressure level differences occur. That is, the arrival time is faster for the sound wave from the
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speaker device 1R, and the sound pressure level is higher for the sound wave from the speaker
device 1R.
[0007]
Therefore, the sound image at the listening position deviated from the center line M of the
speaker devices 1L and 1R, for example, the sound image at point b is added with the abovementioned sound pressure level difference and the preceding effect by the time difference as
shown by arrows in FIG. In the direction of the speaker device 1R, the position is significantly
offset. For this reason, the sound stage in the case of reproducing a normal stereo signal is one
that is offset to the side of the speaker device 1R (shown by a two-dot chain line Lb).
[0008]
With regard to the method of reproducing 2-channel stereo sound intended to improve the
problem of the above-mentioned deviation of the sound stage, that is, to expand the listening
position where good stereo feeling can be obtained, a method using the directivity of the
conventional speaker has been proposed There is. FIG. 16 shows that the speakers 2L and 2R for
reproducing audio signals of the speaker devices 1L and 1R are attached to the closed cabinets
3L and 3R so that their main axes (reference axes) face inward about 45.degree. This is a method
using the directivity of the speaker itself at mid and high frequencies based on the fact that the
diaphragms of the speakers 2L and 2R have a finite area. Further, FIG. 17 uses bi-directional
(eight-shaped directivity) speakers as the audio signal reproduction speakers 4L and 4R that
handle the middle and high frequencies of the speaker devices 1L and 1R, respectively. It is
attached to baffle plates 6L and 6R in the cabinets 5L and 5R whose front face is opened so that
the main axis faces inward about 45 ° when viewed from the central listening position. The
solid lines aL and aR indicate the directivity of the speakers 4L and 4R, respectively.
[0009]
According to the example shown in FIG. 16 and FIG. 17, by giving directivity to the sound waves
radiated from the speaker devices 1L and 1R, the speaker device at a listening position deviated
from the center line M, for example, point b (see FIG. 15) The sound pressure level of the sound
wave from 1R decreases, the sound pressure level of the left channel of the sound wave from the
speaker device 1L slightly increases, and the sound pressure level difference based on the
difference in distance attenuation between the left and right channels is corrected. The listening
position where a good stereo feeling can be obtained is expanded.
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[0010]
However, according to the example shown in FIG. 16, when directivity is to be provided from a
lower frequency, it is necessary to use speakers 2L and 2R having a large aperture, and the
system configuration It becomes large.
Further, according to the example shown in FIG. 17, in order to widen the lower limit of the
reproduction band, it is necessary to increase the baffle plates 6L and 6R to which the speakers
4L and 4R are attached, as in the example shown in FIG. The system configuration becomes
large.
[0011]
Therefore, the present invention provides a stereo speaker device capable of expanding a
listening range where a good stereo feeling can be obtained with a relatively small system
configuration.
[0012]
According to the present invention, there is provided a left channel speaker device having a first
speaker for reproducing a left channel audio signal, and a right channel speaker having a second
speaker for reproducing a right channel audio signal. In the stereo speaker device including the
device, the first speaker unit configured by the first speaker of the left channel speaker device
and the second speaker unit configured by the second speaker of the right channel speaker
device are respectively The first speaker of the left-channel speaker device and the second
speaker of the right-channel speaker device have directivity obtained by a combination of both
directivity and omnidirectionality with maximum sensitivity on the front main axis of the speaker
Each of the main axes is inclined counterclockwise and clockwise with respect to the front
direction of the speaker box by a first angle Those attached to the speaker box.
[0013]
The present invention also relates to a speaker apparatus for left channel having first and second
speakers for reproducing left channel audio signals, and a speaker apparatus for right channels
having third and fourth speakers for reproducing right channel audio signals. A speaker unit
comprising the second speaker of the left channel speaker device and a second speaker unit
comprising the fourth speaker of the right channel speaker device The first speaker of the left-
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channel speaker device and the third speaker of the right-channel speaker device have directivity
obtained by a combination of two-directionality and omnidirectionality with maximum sensitivity
on the front main axis of It is attached to the speaker box so that its main axis coincides with the
front direction of the speaker box. The second speaker of the speaker device and the fourth
speaker of the right channel speaker device respectively have their main axes inclined by a first
angle in a counterclockwise direction and a clockwise direction with respect to the front direction
of the speaker box Attached to the
[0014]
The main axes of the speakers constituting the first and second speaker units for reproducing the
audio signals of the left and right channel speaker devices are directed inward as viewed from
the listening position on the center line of both speaker devices. .
Therefore, due to the directivity obtained by the combination of the directivity and the omnidirectivity of the first and second speaker parts, the difference in distance attenuation between
the left and right channels is different at the listening position out of the center line of both
loudspeakers. The sound pressure level difference based on it is corrected, and the listening
range which can obtain a good stereo feeling is expanded.
[0015]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the
present invention will be described below.
FIG. 1 shows a stereo speaker device 10 according to a first embodiment, and the speaker device
10 includes a left channel speaker device 11L and a right channel speaker device 11R.
[0016]
The speaker mounting surface 13L is formed between the front surface and the right side surface
of the speaker box 12L that constitutes the speaker device 11L, and the audio signal
reproduction speaker 14L is mounted on the speaker mounting surface 13L.
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In this case, as shown in FIG. 2, the speaker box 12L is such that the main axis MAL of the
speaker 14L is inclined counterclockwise by a predetermined angle γ, for example, 40 ° to 50
° with respect to the front direction FL of the speaker box 12L. Attached to
[0017]
A circular sound wave emission port (opening) 16L covered with the acoustic resistance material
15L is provided on an end surface (upper surface in the drawing) different from the speaker
mounting surface 13L of the speaker box 12L. The sound wave emission port 16L is for radiating
air vibration coming out from the back of the diaphragm of the speaker 14L to the outside as a
sound wave, and an axis penetrating the center thereof extends in the direction of the main axis
(reference axis) of the speaker 14L. Is formed.
[0018]
In this case, an acoustic low-pass filter is constituted by the acoustic capacitance of air in the
speaker box 12L and the acoustic resistance and acoustic mass of the acoustic radiation port
16L. The group delay time in the pass band of the sound wave radiated from the sound wave
emission port 16L through the low pass filter is used, and the speaker device 11L is emitted from
two sound sources, the front surface of the speaker 14L and the sound wave emission port 16L.
Directivity is obtained by combining the omnidirectionality and the omnidirectionality with the
maximum sensitivity on the front main axis of the speaker 14L.
[0019]
In addition, a speaker mounting surface 13R is formed between the front surface and the left side
surface of the speaker box 12R constituting the speaker device 11R, and the audio signal
reproduction speaker 14R is mounted on the speaker mounting surface 13R. In this case, as
shown in FIG. 2, in the speaker box 12R, the main axis MAR of the speaker 14R is inclined at a
predetermined angle γ, for example, 40 ° to 50 ° in the clockwise direction with respect to
the front direction FR of the speaker box 12R. It is attached.
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[0020]
A circular sound wave emission port (opening) 16R covered with an acoustic resistance material
15R is provided on an end surface (upper surface in the drawing) different from the speaker
mounting surface 13R of the speaker box 12R. The sound wave emission port 16R is for
radiating air vibration coming out from the back surface of the diaphragm of the speaker 14R to
the outside as a sound wave, and an axis penetrating the center thereof extends in the direction
of the main axis (reference axis) of the speaker 14R. Is formed. Thus, as in the speaker device
11L described above, the synthetic sound pressure of the sound waves radiated from the two
sound sources of the front surface of the speaker 14R and the sound wave emission port 16R in
the speaker device 11R has maximum sensitivity on the front main axis of the speaker 14R. The
directivity obtained by the combination of omnidirectionality and bidirectionality is given.
[0021]
Here, the principle in which the directivity obtained by the combination of the omnidirectionality
and the bidirectionality as described above is given to the speaker devices 11L and 11R will be
described. Since the speaker devices 11L and 11R are configured in the same manner, only the
speaker device 11L will be described, and the description of the speaker device 11R will be
omitted.
[0022]
An equivalent circuit of a mechanical system obtained by equivalently converting the electrical
system and the acoustic system of the speaker device 11L into a mechanical system is
represented as shown in FIG. In the figure, F is an excitation force that moves the diaphragm, and
in constant voltage drive, it is expressed as in equation (1).
[0023]
S 0 is the equivalent stiffness of the support elastic body of the diaphragm, r 0 is the equivalent
mechanical resistance including the electromagnetic braking resistance, and m 0 is the effective
mass of the diaphragm. s1 is an equivalent stiffness obtained by converting the elasticity of air in
the speaker box into the area of the diaphragm, and is expressed by equation (2), where V is the
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volume of air in the speaker box and A is the effective area of the diaphragm.
[0024]
R1 is the equivalent mechanical resistance obtained by converting the acoustic resistance of the
acoustic resistance material 15L of the sound wave emission port 16L into the area of the
diaphragm, m1 is the structure of the sound wave emission port 16L and the acoustic mass
depending on the sound wave area Equivalent mass converted to V1 is the vibration velocity of
the diaphragm, and V2 is the equivalent vibration velocity obtained by converting the vibration
velocity of the air of the sound wave radiation port 16L into the area of the diaphragm.
[0025]
In the speaker device 11L described above, radiation resistance exists on the diaphragm side of
the speaker 14L and the sound wave emission port 16L, respectively, and the power supplied to
the radiation resistance is radiated into the air as acoustic power. However, the radiation
resistance is an extremely small value compared to r0 and r1 and does not affect V1 and V2, so it
is omitted on the equivalent circuit of FIG.
[0026]
Next, theoretical analysis of synthetic sound pressure of sound waves radiated from two sound
sources of the front surface of the speaker 14L (the front surface of the speaker diaphragm) and
the sound emission port 16L will be performed using FIG. Here, let d be the spatial distance in
the main axis direction of the speaker 14L of the two sound sources of the front surface of the
speaker 14L and the sound wave emission port 16L. In addition, focusing on the unidirectional
component in the horizontal plane of the sound wave radiated from the two sound sources of the
front surface of the speaker 14L and the sound wave emission port 16L, setting the main surface
of the speaker to 0 ° Let θ be the angle between the direction of position and the
counterclockwise direction).
[0027]
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In the figure, when d is 8 to 10 cm and the distance r between the sound receiving position and
the speaker 14L is 1 m or more, the two sound sources of the front surface of the speaker 14L
and the sound emission port 16L have middle and low frequency frequencies. Can be regarded as
a point sound source. Also, the sound wave at the receiving position may be regarded as a plane
wave.
[0028]
When handled in this manner, the sound pressure P1 at the sound receiving position of the
sound wave radiated from the front surface of the speaker 14L is expressed by the following
equation (3) because the vibration speed of the diaphragm is V1.
[0029]
Next, the sound pressure P2 at the sound receiving position of the sound wave radiated from the
sound wave emission port 16L causes a time delay corresponding to the distance d cos θ with
respect to P1, and the air vibration at the back of the diaphragm. Therefore, it has a negative
polarity and is expressed by equation (4).
ただし、d<<rである。
[0030]
Therefore, since the synthetic sound pressure P (θ) is P1 + P2, it is expressed by the equation
(5).
[0031]
Here, the vibration velocity V2 is expressed by the equation (6), as is apparent from the
equivalent circuit of FIG.
[0032]
Equation (6) shows the second-order low-pass filter characteristic, and a group delay time of a
fixed value determined by s1, r1, m1 occurs in the pass band.
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This time delay and the time delay that changes by θ obtained by dcosθ / c in space will
provide directivity combining the directivity and omnidirectionality.
Therefore, when equation (6) is substituted into equation (5) and rearranged, ω / c = k, equation
(7) is obtained.
[0033]
In equation (7), the first term in {} is subjected to series expansion to obtain equation (8).
[0034]
As is apparent from the equation (8), at the frequency of kd << 1, the higher order term of jkd is
omitted, the equation (8) becomes cos θ.
Therefore, the first term in {} of equation (7) represents a bi-directional component. On the other
hand, since the second term and the third term in {} of the equation (7) do not depend on θ, they
represent omnidirectional components.
[0035]
Therefore, when P (θ) is normalized by the sound pressure P (0 °) in the front direction (θ = 0
°) and expressed as shown in equation (9), kd << 1 (10) It is expressed as a formula.
[0036]
As is clear from the equation (10), the synthetic sound pressure P (θ) has directivity obtained by
combining the bidirectional component and the omnidirectional component.
The distribution of both components can be changed by the value of α, which represents the
omnidirectional component. This α represents the ratio of r1 / s1 to d / c, as is apparent from
equation (9). r1 / s1 represents the group delay time in the pass band of the low pass filter
constituted by r1, s1 and m1 in FIG. d / c is the time required for the sound wave to propagate
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through the space distance d in the main axis direction of the two sound sources of the front face
of the speaker 14L and the sound wave emission port 16L.
[0037]
FIG. 5 is a diagram in which the directivity pattern is calculated from the equation (10) when the
value of α is 0.5, 1.0, and 2.0.
[0038]
In the equation (10), if α ≦ 1, P (θ) becomes zero at a certain angle.
However, at α> 1, P (θ) never becomes zero at any angle. Assuming that the angle θ at which P
(θ) becomes zero is θ1 when α ≦ 1, as shown in FIG. 5, θ1 is 180 ° at α = 1, and θ1 is 120
° at α = 0.5. Two directions of 240 °. As described above, P (θ) becomes zero at θ = θ1
because the first or higher order terms of jkd present in the bi-directional component
represented by equation (8) are omitted. However, since the higher order terms actually exist, the
directivity pattern of the directivity component does not become a perfect circle eight as the
frequency increases. As a result, the composite directivity pattern also differs from the basic
directivity pattern shown in equation (10). That is, the directivity is degraded.
[0039]
In order to reduce the degree of directivity deterioration to a higher frequency, the first or higher
order term of jkd present in the directivity component represented by equation (8) can be an
omnidirectional component at an angle To cancel out to higher orders using According to
equations (7) and (8), the first term of jkd in equation (8) can be canceled at a certain angle by
the third term in {} in equation (7).
[0040]
Therefore, regarding the third term in {} of equation (7), assuming the equation (11), and
assuming that the offset angle θ is θ2, the condition of offset is expressed by equation (12). In
the equation (12), cos2θ2 is cos2θ2 ≦ 1 in the range of θ2 = 0 ° to 360 °. Therefore, the
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value of β satisfying the equation (12) is β ≦ 0.5.
[0041]
FIG. 6 shows P (θ) / P at θ angles of 90 ° and 180 °, where the value of β is changed in five
steps from 0 to 1 for the case of α = 1 (unidirectionality). It is the result of calculating ¦
requiring the change by the frequency of (0 degree) based on (7) Formula. Here, the condition of
β = 0 means m1 = 0. However, since m1 can not actually be zero, the condition of β = 0 is not
feasible.
[0042]
As is clear from FIG. 6, the synthetic sound pressure level in the back direction (θ = 180 °) of
the speaker 14L decreases by 20 dB or more compared to the front direction (θ = 0 °) at a low
frequency of kd ≦ 0.4. This is a unidirectional pattern in which the synthetic sound pressure
level in the lateral direction (θ = 90 °) is reduced by 6 dB as compared to the front direction.
However, as the frequency increases, the directivity deteriorates, and the directivity becomes
almost non-existent at the frequency of kdππ. The degree of deterioration of the directivity
differs depending on the value of β.
[0043]
FIG. 7 shows how the directivity pattern at a frequency of kd = 1.5 (f = 1.2 KHz for d = 7 cm)
changes according to the value of β. As apparent from the figure, although the value of β can
not be zero, it is necessary to set it as small as possible in order to obtain good directivity to
higher frequencies. When the value of β is set to 0.5 or less, the frequency of kd = 1.5 appears
to be a substantial upper limit of directivity.
[0044]
The above theoretical examination is about middle and low frequency which can be regarded as
an ideal point sound source in which the front surface of the speaker 14L and the sound
emission port 16L are ideal. However, in practice, since the diaphragm of the speaker 14L and
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the sound wave emission port 16L have a finite area, each of the radiation sound waves itself has
directivity at the middle and high frequencies. Therefore, as described above, it is appropriate to
apply directivity to the middle and low frequencies where the radiated sound waves of the
speaker itself do not have directivity.
[0045]
The directivity of the speaker itself differs depending on the size, shape, and aperture diameter of
the speaker box to which the speaker is attached. However, the limit frequency at which
directivity begins to be applied is in inverse proportion to the aperture of the speaker, and the
theoretical results and the measurement results that are already known are as follows. That is,
assuming that the effective diameter of the speaker diaphragm is D, the limit frequency at which
directivity starts to be applied can be regarded as the frequency satisfying the equation (13).
[0046]
When the equation (13) is expressed by the wavelength λ of the radiation wave, 4D = λ from
the relationship of ω / c = 2π / λ, and the wavelength λ of the radiation wave is four times the
frequency of the diaphragm effective diameter D You can look at it. Therefore, in order to apply
the provision of directivity using the group delay time as described above to the frequency range
below the limit frequency at which directivity starts to be applied, the following setting
conditions are appropriate.
[0047]
In the speaker device 11L, the substantial high frequency limit of directivity may be regarded as
a frequency satisfying the equation (14) as described above.
[0048]
Therefore, it is considered appropriate to set this frequency to a frequency at which directivity
begins to be imparted to the radiation sound of the speaker 14 L itself, that is, a frequency
satisfying the equation (13).
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Therefore, the setting condition is as shown in equation (15) according to equations (13) and
(14).
[0049]
In other words, it is appropriate to set the spatial distance d between the front of the speaker
14L and the sound source in the direction of the main axis of the sound wave emission port 16L
equal to the effective diameter D of the speaker diaphragm. Note that this setting condition holds
for directivity in the range of α = 0.5 to 2.0, centering on single directivity in which the
directivity is α = 1.
[0050]
As apparent from the above description, it is possible to give the speaker devices 11L and 11R
any directivity obtained by the combination of the omnidirectionality and the bidirectionality.
[0051]
In the stereo speaker device 10 shown in FIG. 1, the main axes MAL and MAR of the audio signal
reproduction speakers 14L and 14R are in the front direction of the speaker boxes 12L and 12R
respectively with respect to FL and FR with a predetermined angle γ in a counterclockwise
direction and a clockwise direction. The main axes MAL and MAR of the speakers 14L and 14R
are directed inward as viewed from the listening position (see FIG. 2) on the center line M of the
speaker devices 11L and 11R.
In addition, the speaker devices 11L and 11R have directivity obtained by combining the
directivity with the maximum sensitivity on the front main axes of the speakers 14L and 14R and
the directivity.
[0052]
Therefore, at the listening position out of the center line M of the speaker devices 11L and 11R,
for example, at point b (see FIG. 15), the sound pressure level of the right channel decreases and
the sound pressure level of the left channel slightly increases. Sound pressure level differences
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based on differences in channel distance attenuation are corrected. Therefore, according to the
stereo speaker device 10 shown in FIG. 1, the listening range in which a good stereo feeling can
be obtained can be expanded.
[0053]
The applicant conducted a hearing test in order to confirm that the listening range in which a
good stereo feeling can be obtained is expanded as described above in the stereo speaker device
10 shown in FIG. FIG. 8 shows a speaker device 21 used as a left channel speaker device and a
right channel speaker device in this aural test. The speaker device 21 is given single directivity.
[0054]
The speaker box 22 has a rectangular parallelepiped shape, and the dimensions of the speaker
mounting surface are longitudinal, 8.6 cm wide, 14 cm deep, and the volume of air in the speaker
box is 600 cm 3. A dynamic speaker is used as the audio signal reproduction speaker 23, the
aperture is 8 cm, the effective diameter of the diaphragm is 7 cm, and the effective area is 38.5
cm2. The sonic radiation port 24 is circular and provided on the top surface of the speaker box
22 and has an effective area of 26 cm 2. Further, the spatial distance d between the front of the
speaker 23 and the two sound sources in the sound wave emission port 24 in the main axis
direction is set to 7 cm from the condition of the equation (15).
[0055]
The acoustic resistance of the acoustic resistance material 25 of the sound wave radiation port
24 is r1 = 0.745 (kg / sec) in MKS unit when it is expressed by the equivalent mechanical
resistance converted to the area of the speaker diaphragm from Eqs. (2) and (9). ). Therefore, the
equivalent mechanical resistance r1 'represented by the effective area of the acoustic wave
radiation port 24 is expressed by equation (16), where the effective area of the acoustic wave
emission port 24 is A1. Further, the acoustic resistance density (equivalent mechanical resistance
per unit area) of the acoustic resistance material 25 of the sound wave radiation port 24 is 130.8
(kg / sec · m 2) by dividing the equation (16) by A 1.
[0056]
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15
The solid line a, the alternate long and short dash line b, and the broken line c in FIG. 9 indicate
the output sound pressure directional frequency characteristics of the speaker device 21, and it
can be seen that it has unidirectivity at middle and low frequencies. Further, the reproduction
frequency band (3 dB reduction) in the front direction (0 ° direction) is 300 Hz to 20 KHz.
When the effective diameter of the diaphragm is 7 cm, the limit frequency at which the
directivity of the speaker itself begins to be applied is about 1.2 KHz from the equation (13).
Therefore, by setting d = D = 7 cm, the sound pressure level in the 90 ° direction decreases by
about 6 dB with respect to the sound pressure level in the 0 ° direction at frequencies of about
1.5 KHz or less. The pressure level is reduced by 15 dB to 20 dB, and unidirectivity which is
considered to be practically sufficient is obtained. A solid line d, an alternate long and short dash
line e, and a broken line f in FIG. 9 indicate output sound pressure directional frequency
characteristics when the sound wave emission port 24 is not provided, and omnidirectionality is
obtained at middle and low frequencies.
[0057]
The speaker device 21 shown in FIG. 8 was used as a speaker device for the left channel and a
speaker device for the right channel, and was arranged in the listening room 100 having a
reverberation time of about 0.2 seconds in the state shown in FIG. . In the hearing test, the
listening range in which a good stereo feeling can be obtained was determined by the following
method.
[0058]
That is, the listening position on the center line M of both the speaker devices 21 and 21, for
example, the signal sound (for example, vocal etc.) localized at the center front at the point a is
also the listening position at the listening position deviated from the center line M If the sound is
localized in the direction of the intermediate position (point c) of the two speaker devices 21 and
21 viewed from the point of view, a continuous sound stage is reproduced between the two
speaker devices 21 and 21 at the listening position, and a good stereo feeling is obtained. Will be
Therefore, in the hearing test, attention is paid to the listening position on the center line M of
both the speaker devices 21 and 21, for example, the signal sound localized forward in the center
at point a, and the listening sound at the listening position deviated from the center line M The
range to be localized in the direction of the intermediate position between both speaker devices
21 was determined.
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[0059]
In FIG. 10, the broken line L-1 is good under the condition that the sound wave emission port 24
of the speaker device 21 is closed to form a closed shape, and the main axis of the speaker 23 is
directed in the front direction (parallel to the side wall of the listening room 100). It shows the
boundary of the listening range where a good stereo feeling can be obtained, and a good stereo
feeling is obtained in the range on the central line M side from the broken line L-1. Under this
condition, the listening range in which good stereo feeling can be obtained is limited to a narrow
range.
[0060]
In addition, while the alternate long and short dash line L-2 closes the sound wave emission port
24 of the speaker device 21 to form a closed-type, and the main axis of the speaker 23 faces
inward by 45 °, listening can be obtained with a good stereo feeling. The boundary of the range
is shown, and in the range on the central line M side from the alternate long and short dash line
L-2, a good stereo feeling was obtained. In this condition, the listening range in which a good
stereo feeling can be obtained is considerably expanded compared to the condition.
[0061]
On the other hand, the solid line L-3 opens the sound wave emission port 24 of the speaker
device 21 to make the frequency range of about 1.5 KHz or less unidirectional, and makes the
main axis of the speaker 23 inward by 45 °. Under directed conditions, the boundary of the
listening range where a good stereo feeling can be obtained is shown, and a good stereo feeling
is obtained in the range on the central line M side from the solid line L-3. In this condition, the
listening range in which a good stereo feeling can be obtained is further expanded as compared
to the condition. This indicates that the directivity of the low frequency band greatly affects the
sound image localization at the listening position deviated from the center line M of the two
speaker devices 21 and 21.
[0062]
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The effect of expanding the listening range in which a good stereo feeling can be obtained by
such single directivity can be considered as follows. For example, in FIG. 10, the direction of
point d of the speaker device 21 for the left channel is about 10 from the main axis of the
speaker 23 at the listening position considerably deviated from the center line M of both speaker
devices 21 and 21. Although the direction is shifted (θθ10 °), it can be regarded as the
direction of the maximum sensitivity of the speaker device 21 in this degree of shift.
[0063]
On the other hand, the direction of point d of the speaker device 21 for the right channel is a
direction (θθ85 °) deviated by about 85 ° from the main axis of the speaker 23. Therefore,
the sensitivity of the speaker device 21 for the right channel is 0.55 which is 5.2 dB lower than
the maximum sensitivity (= 1) as viewed from the directivity pattern of the single directivity
(cardioid) in FIG. . It is considered that the reduction of the sound pressure level due to the
directivity acts to provide good sound image localization also at the point d.
[0064]
In this way, with hypercardioid, the sensitivity at θ = 85 ° is 8.4dB lower than the maximum
sensitivity at 0.38 (see Figure 5), and hypercardioid is better than unidirectional (cardioid) Can
be seen to be effective in expanding the listening range.
[0065]
Unidirectionality (cardioid) has a component ratio of bi-directionality to omnidirectionality of 1:
1, while hypercardioid has a component ratio of 1: 0.5, and bi-directionality components are
omnidirectional It is twice the sex component.
However, if the component ratio of the bi-directional component becomes higher than this, the
lower limit of the reproduction band becomes narrow, so from the practical point of view, it is
from uni-directional (cardioid) to hyper-cardioid A directivity with a range of directivity patterns
is appropriate.
[0066]
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Further, when the main axis of the speaker 23 is directed inward of both the speaker devices 21
and 21, if the inward is directed too far, for example, the sound pressure of the right channel
speaker device 21 when listening at point d in FIG. Since the level is significantly reduced in the
high range due to the directivity depending on the diameter of the speaker diaphragm, the sound
quality is insufficient for the high sound. Therefore, in view of both the effect of expanding the
listening range and the sound quality, the inward angle is suitably in the range of 40 ° to 50 °.
[0067]
Next, a second embodiment of the present invention will be described. FIG. 11 shows a stereo
speaker device 30 according to a second embodiment, and the speaker device 30 is configured of
a left channel speaker device 31L and a right channel speaker device 31R.
[0068]
The speaker device 31L is a two-way type in which a woofer 33L and a tweeter 34L constituting
a speaker for reproducing an audio signal are attached to the front surface of a substantially
rectangular speaker box 32L. The woofer 33L and the tweeter 34L are attached to the front side
of the speaker box 32L such that the main axes thereof face the front direction of the speaker
box 32L. Further, the upper portion of the corner formed by the front surface and the right side
surface of the speaker box 32L is cut away to form a speaker attachment surface 35L, and the
audio signal reproduction speaker 36L is attached to the attachment surface 35L. In this case, as
shown in FIG. 12, the speaker box 32L is such that the main axis MAL of the speaker 36L is
inclined counterclockwise by a predetermined angle γ, for example, 40 ° to 50 ° with respect
to the front direction FL of the speaker box 32L. Attached to
[0069]
In addition, a circular sound wave emission port (opening) 38L covered with the acoustic
resistance material 37L is provided on an end face (upper surface in the drawing) different from
the speaker attachment surface 35L of the speaker box 32L. The sound wave emission port 38L
is for radiating air vibration coming out from the back surface of the diaphragm of the speaker
36L to the outside as a sound wave, and an axis penetrating the center thereof is formed to
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extend in the direction of the main axis of the speaker 36L. . Although not described above, in the
speaker box 32L, the box portion to which the speaker 36L is attached is separated from the
other box portions.
[0070]
In this case, an acoustic low-pass filter is constituted by the acoustic capacitance of air in the box
portion to which the speaker 36L of the speaker box 32L is attached, and the acoustic resistance
and acoustic mass of the acoustic wave emission port 38L. Then, the group delay time in the pass
band of the sound wave radiated from the sound wave emission port 38L through the low pass
filter is used, and the front side of the speaker 36L and the sound wave emission are used in the
speaker unit composed of the speaker 36L The directivity is obtained in which the synthetic
sound pressure of the sound waves radiated from the two sound sources of the opening 38L is
obtained by the combination of the omnidirectionality and the bidirectionality having the
maximum sensitivity on the front main axis of the speaker 36L.
[0071]
The speaker device 31R is a two-way type in which a woofer 33R and a tweeter 34R constituting
a speaker for reproducing an audio signal are attached to the front surface of a substantially
rectangular speaker box 32R. The woofer 33R and the tweeter 34R are attached to the front side
of the speaker box 32R such that the main axes thereof face the front direction of the speaker
box 32R. In the speaker box 32R, the upper part of the corner formed by the front surface and
the left surface is cut away to form a speaker mounting surface 35R, and the speaker 36R for
audio signal reproduction is mounted on the mounting surface 35R. In this case, as shown in FIG.
12, in the speaker box 32R, the main axis MAR of the speaker 36R is inclined at a predetermined
angle γ, for example, 40 ° to 50 ° in the clockwise direction with respect to the front direction
FR of the speaker box 32R. It is attached.
[0072]
In addition, a circular sound wave emission port (opening) 38R covered with the acoustic
resistance material 37R is provided on an end face (upper surface in the drawing) different from
the speaker attachment surface 35R of the speaker box 32R. The sound wave emission port 38R
is for radiating air vibration coming out from the back surface of the diaphragm of the speaker
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36R to the outside as a sound wave, and an axis penetrating the center thereof is formed to
extend in the direction of the main axis of the speaker 36R. . Although not described above, the
box portion to which the speaker 36R is attached is separated from the other box portions inside
the speaker box 32R.
[0073]
In this case, an acoustic low-pass filter is constituted by the acoustic capacitance of the air in the
box portion to which the speaker 36R of the speaker box 32R is attached and the acoustic
resistance and acoustic mass of the acoustic wave emission port 38R. Then, the group delay time
in the pass band of the sound wave radiated from the sound wave emission port 38R through
this low pass filter is used, and the front surface of the speaker 36R and the sound wave emission
are used in the speaker unit composed of the speaker 36R of the speaker device 31R. Directivity
is obtained in which the synthetic sound pressure of the sound waves radiated from the two
sound sources of the mouth 38R is obtained by the combination of the omnidirectionality and the
bidirectionality with the maximum sensitivity on the front main axis of the speaker 36R.
[0074]
In the stereo speaker device 30 shown in FIG. 11, the main axes MAL and MAR of the audio
signal reproduction speakers 36L and 36R are a predetermined angle γ in a counterclockwise
direction and a clockwise direction with respect to the front directions FL and FR of the speaker
boxes 32L and 32R, respectively. The main axes MAL and MAR of the speakers 36L and 36R are
directed inward as viewed from the listening position (see FIG. 12) on the center line M of the
speaker devices 31L and 31R. In addition, the speaker units configured by the speakers 36L and
36R of the speaker devices 31L and 31R have directivity obtained by a combination of the
directivity and the omnidirectionality having the maximum sensitivity on the front main axes of
the speakers 36L and 36R, respectively. doing.
[0075]
Therefore, at the listening position out of the center line M of the speaker devices 31L and 31R,
for example, at point b (see FIG. 15), the sound pressure level of the right channel decreases and
the sound pressure level of the left channel slightly increases. Sound pressure level differences
based on differences in channel distance attenuation are corrected. Therefore, according to the
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21
stereo speaker device 30 shown in FIG. 11, as in the stereo speaker device 10 shown in FIG. 1,
the listening range in which a good stereo feeling can be obtained can be expanded.
[0076]
The applicant conducted a hearing test in order to confirm that the listening range in which a
good stereo feeling can be obtained is expanded as described above in the stereo speaker device
30 shown in FIG. FIG. 13 shows a speaker device 40 used as a left channel speaker device and a
right channel speaker device in this audibility test. The speaker device 40 has a speaker device
21 shown in FIG. 8 disposed above the speaker device 41. As shown in FIG. The speaker device
41 is a two-way type in which a woofer 43 with a diameter of 14 cm and a tweeter 44 with a
diameter of 8 cm are attached to a speaker box 42 with a width of 20 cm, a depth of 22 cm and a
height of 30 cm.
[0077]
The speaker apparatus 40 shown in FIG. 13 was used as a speaker apparatus for the left channel
and a speaker apparatus for the right channel, and was arranged in the listening room 100
having a reverberation time of about 0.2 seconds in the state shown in FIG. . In this case, the
listening range in which a good stereo feeling can be obtained was determined by the same
method as in FIG. The two-way speaker device 41 is disposed so that the main axes of the woofer
43 and the tweeter 44 face in the front direction (parallel to the side wall of the listening room
100). Further, in a state in which the main axis of the speaker 23 of the speaker device 21 is
directed in the front direction, the sound pressure level at the listening position on the center line
M of both speaker devices 40, 40 of this speaker device 21 is, for example, 2 ways It is set so as
to be 3 dB lower than the sound pressure level of the speaker device 41 of the system.
[0078]
In FIG. 14, a broken line L-4 indicates a listening range where good stereo feeling can be
obtained under the condition where the sound wave emission port 24 of the speaker device 21 is
closed to form a closed shape and the main axis of the speaker 23 is directed to the front A
boundary is shown, and in the range on the central line M side from the broken line L-4, a good
stereo feeling was obtained. Under this condition, as in the case of the condition of FIG. 10, the
listening range in which a good stereo feeling can be obtained is limited to a narrow range.
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[0079]
In addition, while the alternate long and short dash line L-5 closes the sound wave emission port
24 of the speaker device 21 to form a closed shape, listening can be obtained with a good stereo
feeling under the condition that the main axis of the speaker 23 faces inward by 45 °. The
boundary of the range is shown, and in the range on the central line M side from the alternate
long and short dash line L-5, a good stereo feeling was obtained. In this condition, the listening
range where a good stereo feeling can be obtained compared with the condition is considerably
expanded, but it is slightly narrower than the condition in FIG.
[0080]
On the other hand, the solid line L-6 opens the sound wave emission port 24 of the speaker
device 21 to make the frequency range of about 1.5 KHz or less unidirectional and makes the
main axis of the speaker 23 inward by 45 °. Under the conditions directed, the boundary of the
listening range where a good stereo feeling can be obtained is shown, and a good stereo feeling
is obtained in the range on the central line M side from the solid line L-6.
[0081]
In this condition, the listening range in which a good stereo feeling can be obtained is further
expanded as compared to the condition.
The sound pressure is smaller than that in the case of the condition of FIG. 10, but the sound
pressure is the above mentioned sound wave emitted from the small uni-directional speaker
device 21 as the sound wave emitted by the two-way speaker device 41 facing the front. It can be
said that the addition under the level condition has a significant effect on the expansion of the
listening range where a desirable stereo feeling can be obtained.
[0082]
In this case, as the directivity of the speaker device 21 to be added, directivity having a directivity
pattern ranging from cardioid to hypercardioid is suitable as described above. In addition, it is
10-05-2019
23
appropriate for the set angle of the main axis of the directional speaker to be directed in the
range of 40 ° to 50 ° inward.
[0083]
According to the present invention, the main axes of the speakers for reproducing audio signals
of the left and right channel speaker devices are directed inward as viewed from the listening
position on the center line of both speaker devices, Since the speaker unit configured by the
speaker for audio signal reproduction of the speaker device has directivity obtained by
combining the directivity and omnidirectionality, the distance between the left and right channels
at the listening position deviated from the center line of both speaker devices The sound
pressure level difference based on the difference in attenuation is corrected, and the listening
range in which a good stereo feeling can be obtained can be expanded. In addition, the speaker
unit configured by the speakers for reproducing audio signals of both speaker devices has
directivity obtained by a combination of the directivity and the omnidirectionality, for example, a
group delay of sound waves radiated from the sound wave radiation port. It is possible to obtain
directivity by using time, and it is possible to miniaturize the system configuration as compared
with the conventional one using the directivity of the speaker itself or using the bi-directional
speaker. .
[0084]
Brief description of the drawings
[0085]
1 is a perspective view showing a stereo speaker apparatus according to the first embodiment.
[0086]
2 is a diagram showing the orientation of the main axis of the speaker for reproducing the audio
signal.
[0087]
3 is a circuit connection diagram showing an equivalent circuit of the mechanical system.
[0088]
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24
4 is a diagram for theoretical analysis of synthetic sound pressure.
[0089]
It is a figure which shows the directivity pattern at the time of changing FIG. 5 (alpha).
[0090]
It is a figure which shows the change of the directivity frequency characteristic by the value of
FIG. 6 (beta).
[0091]
It is a figure which shows the directivity pattern at the time of changing FIG. 7 (beta).
[0092]
8 is a perspective view showing a speaker device used in the hearing test.
[0093]
9 is a diagram showing the output sound pressure directional frequency characteristics of the
speaker apparatus of FIG.
[0094]
<Figure 10> It is the figure in order to explain the result etc of hearing test.
[0095]
<Figure 11> It is the strabismus figure which shows the stereo speaker device as the form of 2nd
execution.
[0096]
<Figure 12> It is the figure which shows the direction of the principal axis of the speaker which
reproduces the sound signal.
[0097]
13 is a perspective view showing a speaker device used in the hearing test.
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[0098]
<Figure 14> It is the figure in order to explain the result etc of hearing test.
[0099]
15 is a diagram for explaining a stereo speaker device.
[0100]
<Figure 16> It is the figure which shows one example in order to extend the listening range
where satisfactory stereo impression is obtained.
[0101]
17 is a diagram showing another example for expanding the listening range where a good stereo
feeling can be obtained.
[0102]
Explanation of sign
[0103]
10, 30 Stereo Speaker Device 11L, 31L Left Channel Speaker Device 11R, 31R Right Channel
Speaker Device 12L, 12R, 32L, 32R Speaker Box 13L, 13R, 35L, 35R Speaker Mounting Surface
14L, 14R, 36L, 36R Voice Signal Loudspeaker for playback 15L, 15R, 37L, 37R Acoustic
resistance material 16L, 16R, 38L, 38R Acoustic wave radiation port 33L, 33R Woofer 34L, 34R
tweeter
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