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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a curve diagram showing an example of
frequency sound pressure characteristics of a conventional flat type speaker, and FIG. 2 is a cross
sectional view showing a disk shaped diaphragm having a sandwich structure incorporated in the
speaker. Fig. 3 is a cross-sectional view showing a flat type speaker according to the present
invention, and a brush 4 is an ms diagram showing the same frequency sound pressure
characteristics, in which 1 is a core material, 2- is a skin material, 10 is a disk shaped diaphragm
Reference numeral 17 denotes a voice coil, and reference numeral 20 denotes a transmission
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flat loudspeaker.
Most of the existing speakers are cone-shaped loudspeakers that incorporate a cone-shaped
diaphragm into the field & 11 evils. This cone type speaker has a defect that the cavity
phenomenon occurs and the frequency sound pressure characteristic is disturbed because the
front surface of the diaphragm is concave. Flat-type speakers are in the limelight as a speaker
that overcomes this drawback. This flat type speaker is an excellent feature that it can be made
as thin as the speaker / Z2e; 9r2 as well as solving the above-mentioned drawbacks? On the
other hand, on the other hand, it is required to have a large bending stiffness compared to that of
the cone type. As a method of obtaining a large bending rigidity, it is known that the diaphragm
is made to have a sandwich structure in which both the front and back sides of the core material
are held by the skin material VC. On the other hand, a bundle of diaphragms is preferably a light
$ 1 to directly affect the efficiency of the speaker. As this light material, sintered porous body,
felt metal and metal ternary "4 + A 7 J" structure 1 to 1 mesh-like structure 1 "0" 4 etc etc.
Among the porous structures, the ternary network-like structure has a sponge shape having a
three-dimensionally uniform network, and it is possible to receive a stress concentration in a
part, and a large strong Ji 'is obtained even in high pore 1IAvc. Have. The metal ternary network
structure is described in detail in Japanese Examined Patent Publication No. 47-10524, and is
currently being developed with an alloy such as nirikel, chromium, copper or A having a sieve
hole Li. . In particular, the Niraquel ternary network provides a stable characteristic wheel with a
high porosity of 98 to 99%. The first factor is the thickness t1 = 2.5 M as shown in the second
factor. 6) A two-coer ternary network structure having a porosity of 98% is used as a core
material (1), and the thickness t, z = 50. Surface acoustic material made of aluminum foil of lIm
(frequency sound pressure characteristics of a flat type speaker in which a disk-shaped
diaphragm (3) having a diameter 251 (21 t) made to the right is incorporated in one field portion
not shown) FIG. In the same figure, the beak 8 of 1Ith corresponds to the first surface circular
mode, and the beak B corresponds to the 442 next nodal circular mode. In general, in a diskshaped diaphragm, the resonance frequency af for generating the above-mentioned nodal-circle
mode is ··· · · C, however, k ′ circumference number parameter R radius D ° of the micro-plate
is a stiffness σ · surface density Desired. As for the value of the frequency halometer, the
influence of the voice coil and the edge is considered as ThJ, and k = 7.3 in the first nodal circle
mode, and -66 in the second nodal evening circle mode. Used in
The present invention suppresses the generation of the t pressure beak A due to the first section
4-circle mode having such frequency sound pressure characteristics, and will be described in
detail below with reference to FIG. 5 and later. . The fifth factor is an embodiment of the flat type
Noubika of the present invention, and QO is a disc-shaped diaphragm which is mounted in FIG. A
metal porous structure such as a body is used as a core material (1), and a skin material such as
aluminum foil (two bars 21 are wound to form a sand proof structure) is used on the front and
back sides. In the field section having a till μ-shaped field air outlet, the field section +111 has a
bottom plate α4 with center pole ttat erected in the center, an annular ferrite magne- toro, and
an annular type)- p17 Ray) tlf9 and t11 form a so-called external-magnet-shaped shape formed
by stacking in the past. u 71 is a cylindrical coil bobbin (winding) wound with a winding α
casting 9 Hois coil, a field connected concentrically with one end of the fine movement &
screaming and a cone in which the voice coil σ に is arranged at the other end The transmission
member gm is a five transmission member that transmits the vibration coil QG of the voice coil
α in the magnetic air gap @uK via the transmission yarn comprising the coil bobbin. The feature
of the present invention lies in the joint work place of the above-mentioned transmission lt1
member 11 and withdrawal 11 Fil & Qtl. That is, the nodal circle of the first nodal circular mode
in the disk-like diaphragm 00 is generated 1s 81 T ′ ′ ′ C of 0.68 H from the center of the
ordinary plate OU, and the beak of the nine frequency pressure characteristics shown in FIG.
Since A is emitted m, one end of the diameter-radiating member ciO is connected concentrically
at a portion about 0.66 times the height of the plate 1 plate α1 which is the generation
destination of this nodal circle, and the ratio first order It suppresses the circle mode. Fig. 4
shows the frequency bamboo pressure characteristics of a type 1 sneaker according to the
invention. At this time, the movement & LlO used was a disc-shaped diaphragm QO with a
diameter of 25 tM, which had the same core structure (1) as the one exhibiting the
characteristics of quasi-Fig. As the member l, a carphone mixed cone of specific elasticity ′ ′ $
6.3 (xm / 5118) 2 was used. In the same (2), the beak C is the same loss as the beak B of 81 (2)
due to the second nodal circle mode. As apparent from this 184 FIG. 271 etc., the beak A caused
by the first nodal circle mode does not occur, and the flat MS number characteristic range can be
expanded. 6 In the above description, the transmission system for transmitting the vibration of
the voice coil port to the diaphragm αQ is composed of the coil bobbin (至) and the cone-like
transmission member 4, but the coil bobbin (() and the transmission member 4 The winding
machine α1 may be wound directly on a funnel-shaped member in which the coils are
integrated, and if the radius r of the coil bobbin (r) satisfies the relationship of r−0, 68R It is also
possible to connect.
As is apparent from the above description, the flat type speaker according to the present
invention is concentric with a disc-shaped diaphragm having a sandwich structure having a metal
porous complex as a core material at about 0.68 times the diameter of the diaphragm. Since the
transmission system for transmitting the driving force of the voice coil is connected, the first
nodal circular mode can be suppressed, and the nodal circular heater in the frequency sound
pressure characteristic can be eliminated. Therefore, since the diaphragm performs the faithful
piston movement over a wide range, it can be attributed to 5 of the flat I @ wave number sound
pressure characteristics.