JPS5834868Y2 - flat speaker - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flat speaker that reproduces sound by vibrating a flat diaphragm.

Most existing speakers are cone-shaped speakers that incorporate a cone-shaped diaphragm into a magnetic circuit.

This cone-shaped speaker has the disadvantage that the front surface of the diaphragm is concave, which causes a cavity phenomenon, which disturbs the frequency sound pressure characteristics.

Planar speakers have been attracting attention as a speaker that overcomes these drawbacks.

The planar diaphragm incorporated in this planar speaker is required to have greater bending rigidity than that of a cone-type speaker, and the applicant has already proposed a diaphragm that meets this requirement in U.S. Pat. No. 54-47310, etc. .

Furthermore, the applicant of the present application proposed in Utility Model Application No. 54-61559 to suppress the nodal mode by the nodal circle by transmitting the driving force from the voice coil to the nodal position of the plane diaphragm.

The present invention aims to further improve such a speaker and expand the reproduction band, and will be described in detail below with reference to the drawings.

Reference numeral 1 designates a planar diaphragm having high bending rigidity. The diaphragm 1 has a core material 2 made of a metal porous structure such as a nickel ternary network structure, and a skin material 3 such as aluminum foil on both sides of the core material.
, 3 are firmly fixed to form a sand inch structure.

Reference numeral 4 denotes a magnetic circuit having an annular magnetic gap 5, in which a bottom plate 7 with a center pole 6 set in the center, an annular ferrite magnet 8, and an annular top plate 9 are successively stacked. It has a so-called outer magnet type shape.

10 is a voice coil in which a winding 12 is wound around a cylindrical coil bobbin 11; 13 is a cone for suspending the voice coil 10 from a neck portion 14 and disposing it in the magnetic gap of the magnetic circuit 4 so as to be able to freely vibrate; The cone 13 transmits the driving force of the voice coil 10 from the opening 15 to the nodal position of the diaphragm 1.

The cone 13 is formed by mixing pulp fibers with high elastic fibers such as carbon fibers, glass fibers, metal fibers, aromatic polyamide fibers, etc., and has a high specific elasticity JE/p (ρ: heavy density E
: Young's modulus).

The feature of the present invention is that the cone 13 is made of a mixed paper of pulp fibers and high elastic fibers and has a high specific elasticity J, and the nodal position of the flat diaphragm 1 is set to R. In this case, the connection is approximately 0.68H from the center.

That is, by connecting the cone 13 at the nodal position, the nodal mode due to the nodal circle can be suppressed, and by imparting high specific elasticity V177 to the cone 13, the division vibration start frequency of the cone 13 can be suppressed. fr (hereinafter abbreviated as divided frequency fr) can be set outside the reproduction band.

This division frequency fr is given by the following equation, where the half apex angle of the cone 13 is θ, the inner diameter of the opening 15 of the cone 13 is 41, and the frequency parameter is Kf.

The above-mentioned frequency parameter Kf takes a value of Kf#1.12 when the cone 13 is in free vibration, and a value of Kf''; 1.34 is used for convenience when the outer circumference is fixed. When the diaphragm 1 and the voice coil 10 are connected to the neck part 14, K is approximately the middle value between the two.
F#1.20 is used empirically.

Next, for example, in a low-frequency speaker with the radius of the plane diaphragm 1 being R=12C1rL and the aperture including the edges being 30cTL, the half apex angle of the cone 13 is θ=60°, and the opening 15
Substituting the specific value of r = 0.68 R for the inner diameter of and transforming the first equation into an equation regarding the specific elasticity JE7;
The division frequency fr is as follows.

Generally speaking, the specific elasticity -IE7' in the case of the cone 13, which is made only of pulp fibers, shows a value of approximately 1.0 to 2.21 an/sec, so from the second equation, the division frequency fr is 1.16 to
The frequency is 2.55 KHz.

Therefore, when using a pulp cone, the maximum dividing frequency fr is 2.55 KHzL, and the value of 80φ of this dividing frequency fr is usually considered to be the limit of the reproduction band of the speaker, so it is difficult to obtain a speaker with a narrow reproduction band. I can only get it.

- Since the specific elasticity of the cone 13, which is made by mixing high elastic fibers with pulp fibers as proposed in the old book, is high, the reproduction band can be expanded.

For example, add 20% carbon fiber to pulp fiber as high elastic fiber.
When the paper is mixed, the specific elasticity becomes approximately 3.0 km/sec, and the division frequency fr increases to 3.48 KHz from the second equation.

In other words, the limit of the playback band is 3.48KHz x 0.8 = 2.8
Since it is kHz, it can sufficiently cover the band of the low frequency speaker.

As another example, by using a cone to which a metal film is attached after mixing high-elastic fibers, the specific elasticity can be further increased, and the splitting frequency fr can be increased.

This is because the high elasticity fibers have slipperiness, so when they are mixed, the intertwining between the fibers is poor and the characteristics of the high elasticity fibers cannot be fully utilized. This is because the initial purpose can be achieved.

Specifically, after mixing 20% of the above carbon fibers, a nickel film was deposited as a metal film by electroless plating to form a cone 1 with a specific elasticity J107 of 3.6 b/sec.
You can get 3.

In this case, the divided frequency fr is approximately 4.2 KHz, which allows the reproduction band to be further expanded.

FIG. 2 shows an example of its frequency characteristics.

As is clear from the above description, the planar speaker of the present invention has the following features:
A cone made of a mixed material of pulp fibers and high elastic fibers is connected to the nodal position of the flat diaphragm, and the driving force of the voice coil is transmitted to the diaphragm through the cone, so that the nodal circle due to the nodal circle is transmitted to the diaphragm through the cone. The mode can be suppressed and the reproduction band can be expanded by increasing the division frequency.

Furthermore, by attaching a metal film to the cone after it is mixed, the specific elasticity can be increased, so that the reproduction band can be greatly expanded.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the flat speaker of the present invention, and Figure 2 is a curve diagram showing an example of the frequency characteristics of the present invention, where 1 is a flat diaphragm, 4 is a magnetic circuit, 5 is a magnetic gap, and 10 is a voice. The coil and 13 indicate the cone, respectively.

Claims (1)

[Scope of utility model registration request] 1. The opening of a cone formed by mixing pulp fibers and high elastic fibers is connected to the nodal position of the flat diaphragm, and a voice coil is arranged at the neck of the cone, and the voice coil is connected to a magnetic circuit. A built-in flat speaker. 2. The planar speaker according to claim 1, which is a utility model, characterized in that the cone is made of a cone that has been mixed with highly elastic fibers and then has a metal coating attached thereto.