JP2009206914

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DESCRIPTION JP2009206914
To improve the acoustic characteristics of a flat panel speaker. A flat panel speaker (100) has a
diaphragm (110) equipped with a vibrator (not shown) and a duct (120) on the back side of the
diaphragm (110). The duct 120 is configured by arranging a large number of thin and long
tubes, and is disposed with a gap G between itself and the diaphragm 110. The periphery of the
duct 120 is covered with a sealing material 140 made of a sponge-like rubber material. With this
configuration, the sound wave S radiated from the diaphragm 110 travels straight to the back
surface B side, and is prevented from coming around below the front surface, and the acoustic
characteristics are improved. [Selected figure] Figure 1
フラットパネルスピーカー
[0001]
The present invention relates to a flat panel speaker with a duct.
[0002]
Although research is being conducted on small speakers that provide good sound emission,
improvement of the bass radiation characteristics of small speakers is a major issue for both cone
type and flat panel types.
From the sound propagation characteristics, the directionality (directivity) appears in the sound
wave, but the directionality of the sound wave is stronger for higher frequency sound waves and
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weaker for lower frequency sound waves.
[0003]
FIG. 13 shows a conceptual diagram of propagation of 50 Hz sound wave, 500 Hz sound wave
and 10,000 Hz sound wave from the speaker 10. As described above, since sound waves in the
low frequency range do not have directivity, as shown in FIG. 14, sound waves S1 emitted from
the back of the diaphragm wrap around to the front surface of the diaphragm, so the sound
pressure in the low frequency range generated on the front is Since the sound pressure that has
come around from the back is canceled by the sound pressure, the acoustic radiation to the front
(the direction of the listener) is weakened. This phenomenon is referred to as the "round-in"
phenomenon of sound waves, but since this "round-in" phenomenon acts more strongly in the
lower range, it is the main cause of poor bass range characteristics of small-sized speakers. On
the other hand, in the case of an outdoor concert or a guidance broadcast, as shown in FIG. 15,
the sound wave is diffused, so it becomes noise in the vicinity outside the target area of the
broadcast. In such a purpose-of-use speaker, it is desirable to provide directivity to the mid-low
range of the sound wave to be emitted to prevent diffusion.
[0004]
[Speaker Box] The conventional cone-shaped speaker suppresses the above-mentioned "round-in"
phenomenon by putting the speaker in the box to make the bass radiation to the front rich, and
various speaker boxes have been studied. There are closed type, phase reversal type, resonance
box type, etc. in the speaker box, but when the bass characteristic is required, all become large.
[0005]
As shown in FIG. 16, the closed box 21 of the speaker unit 20 absorbs all the acoustic energy
emitted from the back of the speaker 22 into the glass wool 24.
[0006]
As shown in FIG. 17, the phase-reversal type speaker unit 30 is provided with a duct 38 in a part
of the box 31, and sound waves in the reverse-phase bass region emitted from the back of the
speaker are reversed in phase to be sound waves of positive phase. Although the wave length of
100 Hz is about 3.4 m, the required length of the duct is as long as about 1.7 m of a half wave
length to reverse the phase, though it is put forward to improve the radiation level. It is difficult
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to achieve.
[0007]
Therefore, in many cases, a duct is mounted as a resonance tube in a closed box, and resonance
is performed at a low frequency to improve bass characteristics.
The shape is the same as that of the phase inversion type.
Besides this, there is also a speaker called horn type. In this method, sound waves emitted from
the front of the speaker are emitted from a long horn tube. Since the length of the horn is long, it
is not popular because it has the drawback of being larger than a normal speaker box.
[0008]
In recent years, although BOSE Inc. of the United States has invented a "wave guide" system, the
total length of the wave guide is 132 cm, and it does not necessarily achieve the purpose of low
range improvement. As mentioned above, the processing of the sound wave of the antiphase
which comes out of a speaker back is a big problem even now.
[0009]
[Flat panel speaker] There is a flat panel speaker in which the diaphragm of the speaker is
replaced with cone paper and the panel with high bending rigidity is a vibrating plate. As shown
in FIG. 18, a unit 40 of a normal flat panel speaker is composed of a frame 41, a diaphragm 42,
and a vibrator (driver) 44. The main feature of flat panel speakers is their thinness, so they are
often used without being inserted into the speaker box.
[0010]
The flat panel speaker is an acoustic radiation from a surface sound source, and the sound wave
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in the low frequency range has directivity, so that the entrapment phenomenon is small even if it
is not inserted into the speaker box, and the radiation characteristic in the low frequency range is
improved. However, as shown in FIG. 19, since the acoustic radiation from the surface sound
source also theoretically begins to diffuse from 1 / π of the length of one side of the diaphragm,
the size of the diaphragm is limited and the small flat panel is limited. In the speaker, the bass
characteristic is not always satisfied because the wraparound phenomenon can not be
suppressed.
[0011]
The applicant has been researching flat panel speakers, has obtained the following patents, and
has filed several more patents.
[0012]
Patent No. 3599699 Patent No. 3762202 Patent No. 3762400
[0013]
The problem to be solved by the present invention is a speaker for listening to music indoors by
giving directivity to the sound in the middle low range radiated from the diaphragm of the flat
panel speaker to suppress the "round-in" phenomenon. While improving the low-frequency
characteristics of the speaker, while limiting the sound diffusion of the outdoor speaker, the
broadcast area is limited.
[0014]
In order to solve the above problems, the flat panel speaker according to the present invention is
basically provided with respect to a diaphragm panel, a vibrator mounted on the diaphragm
panel, and one of the acoustic emission surfaces of the diaphragm panel. Sound diffusion
suppression duct device composed of a large number of tube-shaped ducts disposed through a
clearance gap, and an elastic material sealing the clearance between the periphery of the sound
diffusion suppression duct device and the diaphragm panel And a sealing member.
In addition, a sound is formed of a diaphragm panel, a vibrator provided on the diaphragm panel,
and a large number of tube-shaped ducts disposed with a gap to both of the acoustic emission
surfaces of the diaphragm panel. A diffusion suppression duct device and a seal member made of
an elastic material that seals a gap between the periphery of the acoustic diffusion suppression
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duct device and the diaphragm panel.
The tubular duct is formed of a honeycomb core, and the axis of the tubular duct is formed to
have an arbitrary angle with respect to the diaphragm panel.
Furthermore, the axis of the tubular duct can also be formed to have a focal point.
[0015]
According to the present invention, the sound quality of the flat panel speaker can be improved.
[0016]
FIGS. 1A and 1B show the basic configuration of the present invention.
On the radiation surface of the diaphragm panel 110 of the flat panel speaker 100, the
diaphragm and a slight gap G were provided, and the diffusion suppressing duct device 120
constituted of innumerable tube-shaped ducts was mounted. The periphery of the gap G is
covered with a sealing material 140. By this device, the air inside the duct 120 is vibrated by the
sound pressure of the diaphragm 110, and the sound pressure is introduced inside the duct 120.
The ducts are parallel, thin and long, so the sound wave S reflects on the inner surface of the
duct, and the sound waves colliding with each other interfere with each other, and the reflections
are repeated, similar to the effect that general "megaphones" have. They interfere with each other
and are emitted from the back surface B. In this process the sound waves are directed in the
direction of the duct. This phenomenon is similar to the principle that light traveling on the inner
surface of the metallic mirror's honeycomb core is reflected, interfered and directed.
[0017]
Since this device suppresses the radiation diffusion of the low-frequency sound, it is possible to
suppress the sneaking phenomenon from the back surface B to the front surface F of the lowfrequency region in the diaphragm panel 110, and improve the low-frequency characteristics of
the music flat panel speaker. It was possible. By controlling the diffusion also in the mid-range
acoustic radiation, it was possible to give direction, so it became possible to limit the area of the
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guidance broadcast and also possible to extend the reach distance. The cross-sectional shape of
the tube of the diffusion suppressing duct device 110 may be circular, hexagonal or tetragonal.
[0018]
2 and 3 show the specific structure of the tube shape of the duct. FIG. 2 shows a structure in
which the duct 220 attached to the diaphragm 210 of the flat panel speaker 200 via the gap G is
a honeycomb core. The periphery of the gap G is covered with a sealing material 240. As shown
in FIG. 3, the duct of the roll core 320 can be used instead of the duct 220 of the honeycomb
core. Specifically, depending on the purpose of use of the speaker, it is necessary to select the
length and thickness of the tube. If the tube is thin, reflection of high-pitched band will come out
and affect the diaphragm to disturb the sound quality.
[0019]
Since it was assumed that the smaller the distance G between the diaphragm panels 210 and 310
and the diffusion suppressing duct devices 220 and 320, the larger the effect, the experiment
was performed with various changes in the distance. In the experiment, if the gap is narrowed,
the sound waves leaked from the gap are also reduced, so it was confirmed that the effect of the
orientation is large, but the limit is about 2 mm from the amplitude of the diaphragm. The
experiment was further advanced, and a method was also tried in which the ducts 220 and 320
were directly attached to the diaphragms 210 and 310 without providing a gap, but the air in the
ducts vibrates together with the diaphragm and the sound waves run in the ducts. Since it was
not, it was confirmed that the directivity of the sound wave can not be given because the
reflection and the interference of the sound wave do not occur. Furthermore, the acoustic
characteristics of the high range deteriorate because the mass of the vibration system increases.
In order to prevent the sound wave from leaking from the gap G between the diaphragm panel
210, 310 and the diffusion suppressing duct device 220, 320, it is necessary to seal the
periphery with a sponge-like rubber material 240, 340 or the like.
[0020]
Embodiment 1 of the Invention A more specific embodiment of the present invention will be
described with reference to FIG. FIG. 4 shows a flat panel speaker 400 for listening to music
indoors, and a gap G is provided on the back surface (back surface) of the panel-like diaphragm
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410 indicated by arrow B, and a diffusion suppressing duct device 420 using a roll core is
mounted. 4 (a) and 4 (b) show a plan view and FIG. 5 shows a cross-sectional view. The size of
the diaphragm panel 410 in the first embodiment of the invention is 40 cm in height and 60 cm
in width. The vibrator 450 attached to the diaphragm panel 410 excites the diaphragm. The
diffusion suppressing duct device 420 exerts a number of tube effects to give directionality to
sound waves radiated rearward from the diaphragm panel 410. Since the sound wave given
directivity is rectilinearly advancing toward the rear for a while, wraparound from the back
surface to the front surface is suppressed, the cancellation of sound pressure is reduced, and the
sound pressure level of the bass region is improved. Although it is necessary to select the core
thickness (tube length) and the cell thickness (tube thickness) according to the purpose, in this
embodiment, it is desirable to reduce the overall thickness (depth dimension) So I tried to reduce
the length of the tube. Tests were repeated with various combinations of core thickness (tube
length) from 20 mm to 90 mm, cell size from 3.2 mm to 12 mm. As a result, good results were
obtained with a core thickness (tube length) of 40 mm and a tube diameter (core cell size) of 8.4
mm. When the cell size (thickness of the tube) was too small in each of the honeycomb core and
the roll core, the sound pressure in the tube increased, and interference due to reflection also
occurred, and the sound quality of the midrange range deteriorated. FIG. 6 shows the
improvement in frequency characteristics. (B) of the figure shows the improvement state of the
bass range by the honeycomb core before improvement and (a). An improvement of about 10 db
was observed in the range of 50 Hz to 300 Hz. The numeral 6040 shown in the figure indicates
that the panel size of the diaphragm is 40 cm high and 60 cm wide.
[0021]
Embodiment 2 of the Invention FIGS. 7 and 8 show an example of a flat panel speaker 500 for an
outdoor stage, and a honeycomb diffusion suppressing duct device 520 through a gap 540 on
the front surface of a speaker diaphragm panel 510. In this example, the acoustic radiation in
front of the speaker is not diffused more than necessary, so the noise outside the listening area is
reduced, the sound pressure level in the listening area is improved, and the acoustic
characteristics (sound quality) are improved. . The diaphragm 510 is circular and has a diameter
of 20 cm, and is vibrated by the vibrator 550. In this case, the duct 520 has a tube length (core
thickness) of 80 mm and a tube diameter (core cell size) of 8.4 mm.
[0022]
Embodiment 3 of the Invention FIG. 9 shows an embodiment in which the present invention is
applied to a wall-mounted speaker 600, in which a honeycomb core constituting the diffusion
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suppressing duct device 620 is cut at 45 degrees diagonally and used. It does not reflect on the
wall surface W1 of the room, but guides the reflected wave to both ends of the speaker and
diffuses and emits from the end. In the past, "wall mounted speakers" have been sought by taking
advantage of the flat panel speaker's characteristics not to take up thickness, but when the
diaphragm approaches the wall of a room, the reflected sound pressure from the wall acts on the
diaphragm Then, the diaphragm is vibrated in the reverse direction, and as a result, the reflected
sound is emitted to the front surface, thereby impairing the sound quality of the radiation sound.
For this reason, since the distance between the diaphragm and the wall surface can not be
reduced, the thickness of the speaker can not be reduced. By applying this embodiment 3, even if
the diaphragm is brought close to the wall surface, the adverse effect due to the reflection from
the wall surface can be reduced.
[0023]
Embodiment 4 of the Invention FIG. 10 shows an embodiment in which the present invention is
applied to a speaker 700 mounted on the lower end of a video screen 760, and the diffusion
suppressing duct in which the honeycomb core is cut at 45 degrees as in Embodiment 3. The
device 720 is mounted on the back. The excitation method, the provision of a gap, and the like
are the same as in the embodiments described above. Since the sound waves of antiphase emitted
from the back of the diaphragm 710 are emitted to the back of the image screen 760, the
reflection of the wall W1 is eliminated, and the adverse effect of the reflection can be avoided. At
the same time, it was also possible to reduce the wraparound of the low range, so that rich bass
characteristics could be obtained. The present invention is applicable not only to video screens
but also to whiteboard panels not shown.
[0024]
Another Embodiment of the Invention The speaker 800 in FIG. 11 is an example in which the
diffusion suppressing duct devices 820 and 822 are mounted on both sides of the diaphragm
panel 810 to increase the effect. It is suitable for guidance broadcasting with a limited area, such
as guidance on the platform of the station. The speaker 900 shown in FIG. 12 is an example in
which the diffusion suppressing duct device 920 having a curved surface is attached to the
diaphragm panel 910 to make the directivity in the middle to high frequency range stronger.
[0025]
Principles of the invention Example using honeycomb core as duct Example using roll core as
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duct Illustration of the indoor panel speaker of the embodiment 1 of the present invention
Section of the indoor panel speaker of the embodiment 1 of the present invention Figure showing
the frequency characteristics Figure of the outdoor panel speaker of the embodiment 2 of the
present invention Figure of the outdoor panel speaker of the embodiment 2 of the present
invention Embodiment 3 of the wall mounted speaker of the present invention The figure of the
screen speaker of the embodiment 4 of the invention The figure of the other embodiment of the
screen of the screen The figure of the other embodiment of the figure of the sound wave The
figure of the propagation of the sound wave Diagram showing the structure of the box Diagram
showing the structure of various speaker boxes Diagram showing the flat panel speaker Diagram
showing the characteristics of the flat panel speaker
Explanation of sign
[0026]
100 flat panel speaker 110 diaphragm panel 120 duct 140 seal material G clearance
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