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The present invention relates to a flat diaphragm for a speaker, and it is an object of the present
invention to provide a flat diaphragm for a loudspeaker capable of reducing a sound pressure
peak at a high frequency limit frequency and expanding an operating frequency band. It is in.
Generally, in the speaker diaphragm, in the use frequency band, it is considered that it is a
condition for obtaining the best speaker characteristics that the sound emission surface is in the
same phase and the piston vibration is perfect. In order to approach this ideal state,
conventionally, light metals such as paper, titanium, and aluminum have been formed into a cone
shape or a dome shape to provide mechanical strength in the vibration direction. However,
speakers using these diaphragms cause resonance of air in the cone and cause disturbance of
frequency characteristics. In recent years, in order to solve these problems, flat diaphragms to
which a honeycomb sandwich structure or the like is applied have come into practical use.
Because of the light weight and high rigidity of the planar diaphragm due to the honeycomb
structure, it is possible to vibrate the piston to high frequencies, and since the radiation surface is
flat, frequency characteristics are not distorted and sound quality is also improved. A balanced
speaker with little sense of distortion is obtained. However, the flat diaphragm made of the
honeycomb sunkite structure is complicated in structure, and requires a large number of
manufacturing processes and various kinds of members in several tens of steps, resulting in a
considerable increase in cost. It was also difficult to make it cheap. In addition, a speaker using a
planar diaphragm made of a honeycomb sandwich structure is driven by a so-called joint drive
system in which a voice coil is adhered to the in-cylinder portion of the diaphragm or the like in
the primary resonance frequency domain and driven. Although the limit frequency fh is
increased greatly, there is a phenomenon that the sound pressure peak at the high limit
frequency fh becomes considerably higher than that of the speaker by the cone paper. Also, there
is a problem that the high sound pressure beak at this high limit frequency fh makes the design
of the speaker system difficult. That is, even when a loudspeaker having a high upper limit
frequency is viewed as a system, it is necessary to flatten the overall frequency characteristic,
and therefore the high sound pressure peak level must be attenuated. Also, there is a problem
that the frequency band used is naturally limited because the level must be lowered from a
considerably low frequency to attenuate the high sound pressure peak level. The present
invention solves such conventional drawbacks, and the drawings of the embodiments and the
well 1 of the present invention show an embodiment of the flat diaphragm for a speaker
according to the present invention.
In FIG. 1, 1 is a core material, and a surface material (not shown) is attached to the surface and
the back surface with an adhesive. The core material 1 is composed of an assembly of six fanshaped small pieces 2. Each fan-shaped small piece 2 is formed into a cross-sectional waveform
as shown in FIG. 1 and has a plurality of parallel ribs 3 ing. The six fan-shaped small pieces 2 are
assembled so that the extension lines of their lips 3 intersect the center line of the core 1. The
nodal circle shape of the first resonance of the plane diaphragm thus configured is formed to be
a waveform centered on a circle of about 68 sides of the outer diameter of the diaphragm as
shown by the broken line 4 in FIG. The reason is that the bending rigidity in the diametrical
direction of the diaphragm is different, and the portion where the core is adhered to the surface
material from the center to the outer periphery is the most rigid and the position of the nodal
circle becomes closer to the outer periphery. And in the opposite position, the position of the
nodal circle approaches the center. Therefore, the positions of the nodes of the entire diaphragm
can be made wavy. The circle shown by the solid line 6 in FIG. 1 is a node circle of a diaphragm
using a conventional centrosymmetric aluminum honeycomb core, and is a nearly round circle. In
the speaker diaphragm described above, a voice coil bobbin is adhered on the node circle and
node driving is performed. In this case, the voice coil bobbin has a circular shape as in the prior
art. At this time, since the node circle has a waveform, it is possible to make the sound pressure
beak of the open threshold frequency fh smooth by driving the perfect circle and the vibration
plate with the waveform voice coil bobbin. is there. Specifically, a diaphragm having a diameter
of 28 cl was created, and the frequency characteristic when the loudspeaker for high-pitched
sound was used was measured. First, as a material for the core material, an inorganic filler made
by Unitika Co., Ltd., an inorganic filler (Silver surface) (trade name Ux-8HEET ') is made to have a
thickness of too μm, and this sheet is heated at a press surface temperature of 190 ° C and a
pressing time of 6 sec. Then, a fan-shaped small piece with a wave-shaped cross section was
formed. This time, when the distance between the lips is 1.2 M, the height is 1, Om + bound.
Then, these small pieces were put together to form a core material, and an aluminum foil (20
μm) as a surface material was attached to both surfaces of the core material using a nylon
adhesive to prepare a diaphragm. The sound pressure frequency characteristics were measured
when a voice coil bobbin of diameter 19 was bonded to this diaphragm to make a speaker for
high-pitched sound, and the result is shown by curve a in FIG. Further, for comparison, frequency
characteristics when using an aluminum honeycomb vibration wave in which a node
conventionally used is a perfect circle are shown by a curve in the same figure.
The frequency characteristics were measured at 1 m / 1 w in the IIS standard BOX. As can be
understood from this result, in the present embodiment, the peak level at the upper limit
frequency fh is reduced by about 7 dB with respect to the conventional one. As described above,
when a core material is formed by collecting fan-shaped small pieces having parallel ribs by
using K and inorganic filler epoxy resin, and a flat material is adhered to both surfaces of the
core material to form a speaker diaphragm, Since the circular shape can be made into a
waveform, it is possible to extend the high frequency limit frequency fh by driving the node with
a circular voice coil bobbin and reduce the sound pressure peak and smooth the frequency
characteristics as a whole. can do. Therefore, measures for the sound pressure peak level can be
reduced to facilitate the design of the speaker system. In addition, the inorganic filler-polyarylate
resin has a relatively large internal loss as compared to the aluminum foil, and contributes to the
reduction of the sound pressure peak level to some extent. Further, the greatest advantage of
using plastic as the core material is that the integral molding can be performed in a short time,
and the production can be performed in about 20 times the number of steps in the case of the
conventional aluminum honeycomb, and the variation in quality can be remarkably improved.
Although plastic is used as the core material in the above-mentioned actual rod example, the
same effect can be obtained even if it is formed of aluminum foil. Also, fan-shaped pieces having
parallel ribs may be assembled so that the extension lines of the ribs are parallel to the center
line of the core material, and three or more fan-shaped pieces may be assembled. . Further, it is
sufficient that the fan-shaped small pieces have a cross-sectional shape formed in a zigzag shape
such as a sawtooth shape other than the waveform. As described above, according to the present
invention, since at least three or more fan-shaped small pieces having a plurality of ribs disposed
at an angle at which they do not converge are gathered and the surface material is attached to
both surfaces of the water core material. The nodal circle of the next resonance mode can be
made into the shape of a waveform. Therefore, the nodal circle of the waveform is node-driven by
the circular voice coil bobbin to expand the high frequency limit frequency and reduce the sound
pressure peak level at the high frequency limit frequency to flatten the frequency characteristics.
It also has the advantage that it is possible to take measures against the attenuation of the sound
pressure peak level on the speaker system design because the sound pressure peak level is small,
and has the advantage of facilitating the system design.
Brief description of the drawings
FIG. 1 shows an embodiment of a flat diaphragm for a loudspeaker according to the present
invention, wherein a is a plan view thereof, b is a cross-sectional view thereof taken along the line
A-A, and FIG. 01 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10 Other one person 鵬 151112 rlA
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