JP4877964B2 - Flat diaphragm speaker - Google Patents

Description

  The present invention relates to a planar diaphragm speaker, and more particularly to a planar diaphragm speaker having a rectangular planar diaphragm.

  There are various types of speakers, which are electroacoustic transducers that convert electrical signals into sound, but electrodynamic type (dynamic type) is the most widely used as the driving method. As the structure of the diaphragm that radiates, a cone-shaped diaphragm having a substantially conical shape is widely used as the most universal one.

  The cone type speaker has a flat frequency characteristic and little distortion in the piston movement region where the diaphragm vibrates together at a low reproduction frequency, but in a frequency band exceeding this, divided vibrations in which each part moves apart. In this region, peaks and dips occur in the frequency characteristics and distortion increases. Further, the cone type speaker has a phenomenon called a dent effect (or an anterior chamber effect) due to the presence of a dent in the front portion of the diaphragm, which disturbs the characteristics.

  Recent audio technology has made rapid progress due to the introduction of digital technology, etc., but with this, the needs for speakers are diversifying and at the same time, high-quality orientation has become prominent. Under such circumstances, as a means for improving the characteristics of a speaker, a planar diaphragm speaker having a planar diaphragm is attracting attention again. Since the flat diaphragm speaker has no depression at the front portion of the diaphragm, the characteristic is not disturbed by the depression effect of the cone type speaker described above, and the directivity is good. On the other hand, since the diaphragm is flat, it has a side face that split vibration is likely to occur. However, by strengthening the rigidity of the diaphragm and devising the drive position, the piston movement range is much more than the cone type speaker. Can be wide.

In order to suppress the divided vibration and widen the piston movement range to make the high frequency reproduction frequency as high as possible, in the flat diaphragm speaker, the node that drives a specific divided vibration node (part that is hard to vibrate) of the diaphragm A driving method called driving is known.
Japanese Examined Patent Publication No. 44-23783 (Patent Document 1) describes a rectangular plate that is driven in the same phase, with the vicinity of the center point on the two nodal lines forming the boundary of each vibration zone of the third vibration mode in the longitudinal direction as the driving point. A type speaker is shown. Japanese Patent Application Laid-Open No. 55-88499 (Patent Document 2) shows one that drives four points in the vicinity of a nodal circle of a divided vibration of a square diaphragm. Japanese Patent Laid-Open No. 63-97099 (Patent Document 3) discloses a configuration in which a voice coil is fixed at or near the intersection of a node of a secondary free resonance mode in the major axis direction and a node in the minor axis direction of a rectangular flat diaphragm. In addition, an expansion of the piston motion region of the diaphragm while suppressing the primary resonance in the minor axis direction is shown. As a specific embodiment, Patent Document 3 exemplifies a configuration in which a total of eight driving points are provided on each of two straight lines parallel to the long side direction.

When a rectangular diaphragm having a ratio of the long side to the short side of about 1.5 to 2.5 is to be driven at 8 points, the conventional arrangement is 2 rows and 4 columns as shown in FIG. It is common. In the figure, reference numeral 2 denotes a voice coil. As described above, a plurality of drive points are arranged on two straight lines parallel to the long side direction. The drive points are driven at 6 points as shown in FIG. 7, and the drive points are driven at 10 points as shown in FIG. Since both have two rows as compared with those in which driving points are arranged on one straight line, the piston region can be expanded and flat reproduction can be performed up to a high frequency band.
Japanese Patent Publication No. 44-23783 JP 55-88499 JP-A 63-97099

  In a flat diaphragm speaker having a diaphragm having a point-symmetric shape with respect to the center, such as a square diaphragm or a circular diaphragm as in Patent Document 2, the divided vibration mode is also substantially pointed. Since it occurs regularly and sequentially, it is possible to set the drive point to suppress this relatively easily, but in the case of a rectangular diaphragm, the appearance of divided vibration is in the long side direction and the short side Since it is generated in a complicated manner in a single direction or a combination of both, it is very difficult to accurately control this.

  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 mode is expressed as (m, n) mode.

  The drive points arranged in two rows as shown in FIG. 5, FIG. 7 and FIG. 9 consider not only the suppression of the divided vibration in the long side direction but also the control of the divided vibration in the short side direction. It is possible to reproduce even the highest frequency band. However, the configuration shown in FIG. 5 can handle up to the 7-node mode in the X direction and the 3-node mode in the Y direction, but suppresses higher-order split resonance than the 8-node mode in the X direction and the 4-node mode in the Y direction. I can't. When the configuration of FIG. 5, FIG. 7 and FIG. 9 is applied to a 160 mm × 80 mm rectangle, the vibration mode is observed, and in each case a (0, 4) mode appears at 5.3 kHz to 5.7 kHz, and the speaker is in the piston region. Can no longer be maintained. 6, 8, and 10 show the sound pressure frequency characteristics of the speakers having the configurations of FIGS. 5, 7, and 9, and the fact that the vicinity of the frequency at which the (0, 4) mode appears is the limit of high-frequency reproduction. Show.

Increasing the number of drive points can expand the piston area to some extent and extend the high range, but considering the ease of manufacturing and the number of parts, cost-effective 8-point drive is a general form as described above. However, the 8-point drive of 2 rows and 4 columns is not sufficient to meet the recent needs for flat reproduction up to higher frequencies.
In view of the above-described problems, the present invention has a simple configuration without increasing the number of driving points more than necessary, and greatly expands the piston region as compared with the conventional two-row array driving method, and has a flat frequency characteristic up to a higher range. An object of the present invention is to provide a flat diaphragm speaker capable of ensuring the above.

The planar diaphragm speaker according to the invention of claim 1 is a planar diaphragm speaker in which a rectangular diaphragm having a ratio of a long side to a short side of 1.5 to 2.5 is driven 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 the length of the long side of the rectangular diaphragm is determined. (A, 0), (A, 0), (A, B) on the coordinates where A, the short side length is B, the long side direction of each vertex is the X axis, and the short side direction is the Y axis, When arranged at (0, B), the coordinates of the eight drive points are divided into lower-order less than (6, 4) modes with six vibration nodes in the long side direction and four in the short side direction. (A / 8, 3B / 16), (A / 2, 3B / 16), (7A / 8, 3B / 16), (5A / 16, B / 2), (11A / 16, B / 2), (A 8, 13B / 16), (A / 2, 13B / 16), (7A / 8, 13B / 16), and the voice coil of the electrodynamic driver is fixed at a position centered around each point. It is characterized by being.

According to the first aspect of the present invention, the conventional driving points are arranged in two rows by a simple configuration in which the driving points are appropriately arranged as 3-2-3 and driven without increasing the driving points more than necessary. Therefore, it is possible to provide a planar diaphragm speaker that can be easily realized at low cost by greatly expanding the piston region and ensuring a flat frequency characteristic up to a higher range.
In addition , since the eight driving points are arranged so as to suppress divided vibrations lower than less than (6,4) modes with six vibration nodes in the long side direction and four in the short side direction. As a result, it is possible to provide a flat diaphragm speaker capable of greatly expanding the piston region as compared with the conventional two-row arrangement and ensuring a flat frequency characteristic up to a higher region.
Further , the coordinates of the eight driving points are ( A / 8 , 3B / 16), (A / 2 , 3B / 16), (7A / 8 , 3B / 16), (5A / 16, B / 2). , (11A / 16, B / 2), (A / 8, 13B / 16), (A / 2 , 13B / 16), (7A / 8, 13B / 16), with the vicinity of each point as the center Since the voice coil of the electrodynamic driver is fixed at the above position, the driving point can be easily calculated if the rectangular size is determined, so that a flat diaphragm speaker that is easy to design and manufacture can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a plan view of a diaphragm of a planar diaphragm speaker according to the present invention. A broken circle shows a position where a voice coil of an 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 is preferably made of a material in which an aluminum skin material is coated on both sides of a core material made of lightweight wood such as a balsa material. Yes. The outer periphery of the diaphragm is attached to a rectangular frame (not shown) via an edge (not shown) so as to vibrate, and the voice coil 2 of the electrodynamic driver is fixed to the back surface of the diaphragm at eight locations indicated by broken lines in the drawing. .

  The center points of the eight voice coils 2 are set according to the following criteria. These points are arranged on three straight lines parallel to the long side from three long sides to the other long side, respectively. The arrangement of 3 rows and 5 columns is different from the conventional one. The three straight lines have a distance from one long side of 3B / 16, that is, a first straight line of 15 mm, a second straight line passing through the midpoint of the short side, and a distance from the other long side of 3B / 16. That is, there are three third straight lines of 15 mm, the distance from the midpoint and both short sides of each of the first straight line and the third straight line is A / 8, that is, 20 mm, and Eight points are set such that the distance from both short sides on the straight line 2 is 5A / 16, that is, 65 mm. Then, the voice coil 2 of the electrodynamic driver is fixed so that each of the eight points is substantially centered. When an input signal is applied to the voice coil 2, the diaphragm 1 is driven in phase at these eight points. Is done.

  The sound pressure frequency characteristic of the planar diaphragm speaker of the present example having the above-described configuration was measured to obtain the characteristic shown in FIG. The flat characteristics without large peaks and dips are extended to nearly 8 kHz, and the frequency characteristics are significantly higher than the conventional drive points with 2 rows, 4 columns, 2 rows, 5 columns, 2 rows, 3 columns, etc. Was confirmed to be improved.

  When the vibration state of the diaphragm of the planar diaphragm speaker of this example was observed, it was confirmed that (6, 4) mode split vibration was generated at 7950 Hz. FIG. 3 schematically shows the state of split vibration in the (6, 4) mode of the diaphragm of the planar diaphragm speaker of this embodiment. In this embodiment, the (6, 4) mode split vibration cannot be suppressed, and it can be said that the vicinity of 7950 Hz where the split vibration occurs is the limit of the high range, in other words, less than the (6, 4) mode. Lower-order mode split vibration can be suppressed, and the piston region is greatly expanded compared to the conventional two-row array drive system in which (0,4) mode split vibration appears. Can be improved.

  The operation of the planar 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. Y-axis direction displacement, 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 a phase opposite to that of the voice coil, thereby suppressing excitation of the divided vibration of the mode. On the other hand, in the (6, 4) mode, as shown in FIGS. 4 (c) and 4 (d), the vibration mode of the abdomen is excited by the in-phase voice coil, so that the divided vibration of the 6, 4) mode appears. It will be.

  In addition, although the present Example illustrated what used the rectangular diaphragm whose aspect ratio of 160 mm x 80 mm is 2 as a diaphragm, it is not limited to this dimension, The ratio of a long side and a short side is 1.5. The same effect can be obtained by applying a wide range of about 2.5 rectangles. The reason why the ratio is set to about 1.5 to 2.5 is that it is close to a square behavior when the ratio is 1.5 or less, and the split vibration in the short side direction is small and can be ignored when the ratio is 2.5 or more. . In addition, the composite material of the aluminum honeycomb and the aluminum skin is used as the material of the diaphragm. However, the present invention is not limited to this, and the same effect can be obtained as long as the material is light and highly rigid. Further, although an electrodynamic type driver is used as a driver, it can be developed to a driver using a piezoelectric type or other driving type driver.

  The speaker of the present invention can be suitably used for a flat diaphragm speaker having a high reproduction limit frequency and a wide directivity, and is particularly used for a rectangular speaker having a ratio of a long side to a short side of about 1.5 to 2.5. The effect is remarkable.

It is a diaphragm top view of the 8-point drive plane diaphragm speaker of this invention. It is a sound pressure frequency characteristic figure of the 8 point drive plane diaphragm speaker of the present invention. It is a schematic diagram explaining the vibration mode of the (6, 4) mode of the 8-point drive planar diaphragm speaker of this invention. It is a schematic diagram for demonstrating the effect | action of the 8-point drive plane diaphragm speaker of this invention. It is a diaphragm plan view of a conventional eight-point driving planar diaphragm speaker. It is a sound pressure frequency characteristic figure of the planar diaphragm speaker of an 8 point drive of a prior art example. It is a diaphragm top view of the 6-point drive plane diaphragm speaker which is another conventional example. It is a sound pressure frequency characteristic figure of the 6-point drive plane diaphragm speaker which is another conventional example. FIG. 10 is a plan view of a diaphragm of a 10-point driven planar diaphragm speaker which is still another conventional example. It is a sound pressure frequency characteristic figure of a 10-point drive plane diaphragm speaker which is other conventional examples.

Explanation of symbols

1 Diaphragm 2 Voice coil 3 First straight line 4 Second straight line 5 Third straight line

Claims (1)

In a flat diaphragm speaker in which a rectangular diaphragm having a ratio of long side to short side of 1.5 to 2.5 is driven by a plurality of electrodynamic drivers, one long side is placed on three straight lines parallel to the long side. Three, two, and three drive points are provided in each row from the side toward the other long side, the length of the long side of the rectangular diaphragm is A, and the length of the short side is B. When arranged at (0, 0), (A, 0), (A, B), (0, B) on the coordinates where the long side direction of the vertex is the X axis and the short side direction is the Y axis, the 8 The coordinates of the drive points are (A / 8, 8) so that the vibration vibrations are less than (6/8) modes less than 6 (6/8) modes in the long side direction and 4 in the short side direction. 3B / 16), (A / 2, 3B / 16), (7A / 8, 3B / 16), (5A / 16, B / 2), (11A / 16, B / 2), (A / 8, 13B / 16), (A / 2, 13B / 1 ), (7A / 8,13B / 16 ) and is, flat diaphragm loudspeakers, characterized in that is obtained by fixing the voice coil of the electro-dynamic driver position around the vicinity of each point.

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