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JP2008109541

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DESCRIPTION JP2008109541
A flat diaphragm speaker in which a rectangular diaphragm is driven at multiple points by a
plurality of electrodynamic drivers. A total of eight drive points are provided on each of two lines
parallel to the conventional long side. In the two-row arrangement provided, control of periodic
vibration in the short side direction is not sufficient, and divided vibration in the (0, 4) mode can
not be suppressed, and divided vibration in the (0, 4) mode is It is not possible to reproduce high
frequencies above the frequency that occurs. A 3-2-3 three-row arrangement in which three, two,
and three driving points are arranged on three rows of lines parallel to the long side of a
rectangular diaphragm. It is possible to suppress divided vibration of lower order than that in the
(6, 4) mode, and it is possible to reproduce to a frequency band higher than the conventional one
with a simple configuration without increasing the driving point more than necessary. [Selected
figure] Figure 1
Flat diaphragm speaker
[0001]
The present invention relates to a flat diaphragm speaker, and more particularly to a flat
diaphragm speaker provided with a rectangular flat diaphragm.
[0002]
There are various types of speakers that are electroacoustic transducers that convert electrical
signals into sound, but electrodynamic type (dynamic type) is most widely used as a drive type,
while sound A cone-shaped diaphragm having a substantially conical shape is widely used as the
most universal one as a structure of a diaphragm that radiates.
11-05-2019
1
[0003]
In the cone type speaker, in the piston movement area where the diaphragm integrally vibrates
at a low reproduction frequency, the frequency characteristic is flat and distortion is small, but in
the frequency band exceeding this, each part moves apart. In this region, peaks and dips occur in
the frequency characteristics and distortion also increases.
In addition, the cone-type speaker has a phenomenon called a dent effect (or an anterior chamber
effect) due to a dent at the front of the diaphragm, which disturbs the characteristics.
[0004]
Recent audio technology has made rapid progress with the introduction of digital technology etc.
Along with this, the needs for speakers are diversified, and at the same time the high quality
intention becomes remarkable.
Under such a background, a flat diaphragm speaker having a flat diaphragm has come to attract
attention as a means for improving the characteristics of the speaker. Since the flat diaphragm
speaker has no dent in the front of the diaphragm, there is no disturbance of the characteristics
due to the dent effect of the above-mentioned cone type speaker, and the directivity is also good.
On the other hand, although the diaphragm has a flat surface, it has a side that split vibration is
likely to occur, but the rigidity of the diaphragm is strengthened and then the piston movement
range is made more remarkable than that of the cone type speaker It can be made wider.
[0005]
In a flat diaphragm speaker, a node for driving a node (a portion which is difficult to vibrate) of a
specific divided vibration of the diaphragm in order to suppress the divided vibration and widen
the piston movement area and to make the reproduction frequency of the high region as high as
possible. A drive scheme called drive is known. In JP-B-44-23783 (Patent Document 1), a flat
plate is driven in the same phase with drive points near the center points on two nodal lines
forming the boundaries between the vibration sections of the third vibration mode in the
longitudinal direction of the rectangle. A loudspeaker is shown. Japanese Patent Application Laid-
11-05-2019
2
Open No. 55-88499 (Patent Document 2) discloses driving of four points in the vicinity of a
nodal circle of divided vibration of a square diaphragm. Further, in Japanese Patent Application
Laid-Open No. 63-97099 (Patent Document 3), a voice coil is fixed at or near the intersection of a
node of the second free resonance mode in the major axis direction of the rectangular flat
diaphragm and a node in the minor axis direction. What expanded the piston motion area |
region of a diaphragm is also shown, suppressing the primary resonance of short diameter
direction. As a specific embodiment, Patent Document 3 exemplifies one in which a total of eight
driving points are provided on each of two straight lines parallel to the long side direction.
[0006]
When driving a rectangular diaphragm with a ratio of long side to short side of about 1.5 to 2.5
at eight points, conventionally, as shown in FIG. 5, the arrangement of two rows and four
columns is used. It is common. Reference numeral 2 in the figure is a voice coil. As described
above, as a plurality of driving points arranged on two straight lines parallel to the long side
direction, one driven at 6 points as shown in FIG. 7 or one driven at 10 points as shown in FIG. In
addition, since two rows are provided as compared to the row in which the drive points are
arranged on one straight line, the piston region can be expanded to reproduce flatly to a high
frequency band. JP-B-44-23783 JP-A-55-88499 JP-A-63-97099
[0007]
In the case of a flat diaphragm speaker provided with a diaphragm having a point symmetrical
shape with respect to the center like a square diaphragm or a circular diaphragm as in Patent
Document 2, the divisional vibration mode is also substantially point-symmetrical. As it occurs
regularly in sequence, it is possible to relatively easily set the driving point to suppress this, but
in the case of a rectangular diaphragm, the form of divided vibration is in the long side direction
and the short side. It is very difficult to control this precisely, as it occurs in a messy fashion,
either alone or in combination.
[0008]
In the present invention, in order to explain the divided vibration mode of such a rectangular
diaphragm, the long side direction is the X axis, the short side direction is the Y axis, and the
number of periodic vibration nodes is m in the X direction and in the Y direction. n (m, n is 0 or a
positive integer) vibration modes are described as (m, n) modes.
[0009]
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The arrangement of two drive points as shown in FIGS. 5, 7 and 9 considers not only the
suppression of divisional vibration in the long side direction but also the control of divisional
vibration in the short side direction. It is possible to reproduce up to a very high frequency band.
However, although the configuration of FIG. 5 can cope with the 7-node mode in the X direction
and the 3-node mode in the Y direction, it suppresses higher-order split resonance than the 8node mode in the X direction and 4-node mode in the Y direction. I can not do it.
When the configuration of FIGS. 5, 7 and 9 is applied to a rectangle of 160 mm × 80 mm, the
vibration mode is observed, and in all cases (0, 4) mode appears at 5.3 kHz to 5.7 kHz, and the
speaker has a piston area Can not be maintained. 6, 8 and 10 show the sound pressure frequency
characteristics of the loudspeakers of the configurations of FIG. 5, 7 and 9, respectively that the
vicinity of the frequency at which the (0, 4) mode appears is the limit of high frequency
reproduction. It shows.
[0010]
By increasing the number of drive points, it is possible to extend the piston area to a certain
extent and extend the high range, but considering the easiness of manufacture and the number of
parts etc., the 8 points drive with good cost performance is a general form as mentioned above.
However, the 2-row, 8-column 8-point drive is not sufficient to meet the recent needs for flatter
reproduction at higher frequencies. In view of the problems described above, the present
invention enlarges the piston area significantly more than the conventional two-row drive system
with a simple configuration without increasing the number of drive points more than necessary,
and flatter frequency characteristics up to higher frequencies. It is an object of the present
invention to provide a flat diaphragm speaker capable of securing the
[0011]
The flat diaphragm speaker according to the invention of claim 1 is a flat diaphragm speaker for
driving a rectangular diaphragm having a ratio of long side to short side of 1.5 to 2.5 by a
plurality of electrodynamic drivers. Three, two, and three drive points are provided in each row
from one long side to the other long side on three parallel straight lines, and eight drive points
11-05-2019
4
are provided 3-2-3. It is characterized in that it is arranged. In the flat diaphragm speaker
according to the invention of claim 2, in the invention according to claim 1, the eight drive points
have six vibration nodes in the long side direction and four vibration nodes in the short side
direction (6, 4). And the lower division mode is arranged to suppress lower order division
vibrations. In the flat diaphragm speaker according to claim 3, in the invention according to
claim 1 or 2, the length of the long side of the rectangular diaphragm is A, the length of the short
side is B, and each vertex is X direction The coordinates of the eight driving points are (0, 0), (A,
0), (A, B), (0, B) on the coordinates with the axis and the short side direction as the Y axis. , (8 / A,
3B / 16), (A / 4, 3B / 16), (7A / 8, 3B / 16), (5A / 16, B / 2), (11A / 16, B / 2) , (A / 8, 13B / 16),
(A / 4, 13B / 16), (7A / 8, 13B / 16), and the voice of the electrodynamic driver at a position
centered on the vicinity of each point It is characterized in that the coil is fixed.
[0012]
According to the first aspect of the present invention, the conventional drive point is arranged in
two rows by a simple configuration in which eight drive points are arranged and driven as 3-2-3
without increasing the drive points more than necessary. Compared with the above, it is possible
to provide a flat diaphragm speaker that can be easily realized at low cost by enlarging the piston
region significantly and securing a flat frequency characteristic to a higher frequency. According
to the invention of claim 2, the eight driving points suppress lower-order divided vibration than
in the (6, 4) mode in which the number of vibration nodes is six in the long side direction and
four in the short side direction. As arranged as described above, it is possible to provide a flat
diaphragm speaker capable of largely expanding the piston area as compared with the
conventional two-row arrangement, and securing a flat frequency characteristic to a higher
frequency. According to the invention of claim 3, the coordinates of the eight driving points are
(8 / A, 3B / 16), (A / 4, 3B / 16), (7A / 8, 3B / 16), (5A). / 16, B / 2), (11A / 16, B / 2), (A / 8, 13B
/ 16), (A / 4, 13B / 16), (7A / 8, 13B / 16), Since the voice coil of the electrodynamic driver is
fixed at a position centered on the vicinity of each point, the driving point can be easily
calculated if the dimensions of the rectangle are determined, so the flat diaphragm speaker
whose design and manufacture are easy Can be provided.
[0013]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0014]
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5
FIG. 1 is a plan view of the diaphragm of the flat diaphragm speaker according to the present
invention, which is indicated by a broken circle is a position where the voice coil of the
electrodynamic driver is fixed.
The diaphragm has a rectangular shape with a long side (A) of 160 mm and a short side (B) of 80
mm, and preferably made of a material coated with an aluminum skin on both sides of a core
made of lightweight wood such as balsa. There is. The outer periphery of the diaphragm is
vibratably attached to a rectangular frame (not shown) via an edge (not shown), and the voice
coil 2 of the electrodynamic driver is fixed to eight positions shown by broken lines in the figure
on the back of the diaphragm. .
[0015]
The center points of the eight voice coils 2 are set based on the following criteria. Three, two,
three points of these points are arranged on three straight lines parallel to the long side from one
long side to the other long side, respectively, 3-2-3 The arrangement of three rows and five
columns is different from the conventional one. The three straight lines are a first straight line
having a distance of 3B / 16 or 15 mm from one long side, a second straight line passing the
middle point of the short side, and a distance of 3B / 16 from the other long side. That is, three
of the third straight lines of 15 mm, and the distances from the middle point and both short sides
of the first straight line and the third straight line on the respective straight lines are A / 8, that
is, 20 mm; Eight points are set such that the distance from both short sides on the 2 straight line
is 5A / 16, that is, 65 mm. The voice coil 2 of the electrodynamic driver is fixed so that each of
the eight points is substantially centered, and when an input signal is applied to the voice coil 2,
the diaphragm 1 is driven in phase at these eight points. Be done.
[0016]
The sound pressure frequency characteristics of the flat diaphragm speaker of the present
embodiment having the above-described configuration were measured to obtain the
characteristics shown in FIG. The flat characteristics without large peaks and dips extend up to
around 8 kHz, and the frequency characteristics are significantly higher than the conventional
drive points arranged in 2-rows, 2-rows, 5-rows, 2-rows, 3-columns, etc. Was confirmed to be
improved.
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[0017]
When the vibration mode of the diaphragm of the flat diaphragm speaker of this example was
observed, it was confirmed that a divided vibration of (6, 4) mode is generated at 7950 Hz. FIG. 3
schematically shows the state of divided vibration of the (6, 4) mode of the diaphragm of the flat
diaphragm speaker of this embodiment. In the present embodiment, the divided vibration in the
(6, 4) mode can not be suppressed, and it can be said that the vicinity of 7950 Hz where this
divided vibration is generated is the high frequency limit, in other words less than the (6, 4)
mode The divided vibration in the lower order mode can be suppressed, and the piston area is
greatly expanded compared to the conventional 2-row array drive method in which the divided
vibration in the (0, 4) mode appears, and the high frequency characteristic is It can be improved.
[0018]
The operation of the flat diaphragm speaker of this embodiment will be described with reference
to FIG. 4A shows the displacement in the Y axis direction in the (0, 4) mode, FIG. 4B shows the
displacement in the X axis direction in the (6, 0) mode, and FIG. 4C shows the displacement in
the (6, 4) mode FIG. 4D schematically shows the relative relationship between the X-axis
direction displacement and the voice coil in the (6, 4) mode. In the (0, 4) mode of FIG. 4 (a) and
the (6, 0) mode of FIG. 4 (b), two voice coils arranged in the center row are arranged in both
rows. It is driven in the reverse phase to the voice coil, thereby suppressing the excitation of the
divided vibration of the mode. On the other hand, in the (6, 4) mode, since the abdomen of the
vibration mode is excited by the voice coil of the same phase as shown in FIGS. 4C and 4D, the
divided vibration of the 6, 4) mode appears It will be.
[0019]
Although this embodiment exemplifies a rectangular diaphragm having an aspect ratio of 2 of
160 mm × 80 mm as the diaphragm, the ratio of the long side to the short side is 1.5 without
being limited to this size. The same effect can be obtained by widely applying to a rectangle of
about -2.5. The ratio is set to about 1.5 to 2.5 because the behavior is close to a square behavior
at 1.5 or less, and the split vibration in the short side direction has a small effect and can be
ignored at 2.5 or more. . In addition, although a composite of an aluminum honeycomb and an
aluminum skin is used as the material of the diaphragm, the same effect can be obtained as long
as the material is lightweight and has high rigidity as well as this. Furthermore, although the
11-05-2019
7
electrodynamic type was used as the driver, it is also possible to expand to one using a
piezoelectric type or other drive type driver.
[0020]
The speaker according to the present invention can be suitably used for a flat diaphragm speaker
requiring a high reproduction limit frequency and wide directivity, and in particular, a
rectangular speaker having a ratio of long side to short side of about 1.5 to 2.5. The effect is
remarkable.
[0021]
It is a diaphragm top view of the eight-point driving plane diaphragm speaker of this invention.
It is a sound pressure frequency-characteristics figure of the eight-point driving plane diaphragm
speaker of this invention. It is a schematic diagram explaining the vibration mode of (6, 4) mode
of 8 point drive plane diaphragm speaker of this invention. It is a schematic diagram for
demonstrating the effect | action of the 8 point | piece drive plane diaphragm speaker of this
invention. It is a diaphragm top view of the flat diaphragm speaker of eight-point drive of a prior
art example. It is a sound pressure frequency-characteristics figure of the flat diaphragm speaker
of eight points drive of a prior art example. It is a diaphragm top view of the flat diaphragm
speaker of the 6 point drive which is another prior art example. It is a sound pressure frequencycharacteristics figure of the flat diaphragm speaker of six points drive which is another prior art
example. FIG. 10 is a plan view of a diaphragm of a flat diaphragm speaker of ten-point drive
according to still another conventional example. It is a sound pressure frequency-characteristics
figure of the flat diaphragm speaker of 10 points drive which is further another prior art
example.
Explanation of sign
[0022]
1 diaphragm 2 voice coil 3 first straight line 4 second straight line 5 third straight line
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