JPS5816314Y2 - flat speaker - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flat speaker having a circular flat diaphragm.

The most commonly used diaphragm shapes in electrodynamic speakers are cone and dome shapes.

The reason why a plane diaphragm, which is the simplest and easiest to manufacture, is not used is because it is the diaphragm shape that is most susceptible to divided vibration.

By making the diaphragm cone-shaped or dome-shaped, the frequency of divided vibration can be increased, and the reproduction band of the speaker can be expanded.

For example, in a cone-shaped speaker with a diameter of 25crr1, if a diaphragm made of natural fiber is used, the frequency will be approximately 2 to 4 KHz.
is the limit frequency of the high range, and has a sufficient band to be used as a bass speaker.

However, since cone speakers have depressions in the shape of their diaphragms, resonance-like phenomena occur in those areas, resulting in peaks and valleys in the sound pressure characteristics and uneven phase characteristics.

A flat speaker is used to solve this problem, and the present invention relates to an improvement of this flat speaker.

FIG. 1 shows a cone-shaped diaphragm in an infinite baffle, where 1 is the cone-shaped diaphragm, 2 is the baffle plate, and A is the observation point.

Piston vibrates with constant acceleration of cone (integrated movement back and forth)
The sound pressure characteristics on the front axis in this case are K as shown in Figure 2.
Peaks and takes occur when a is 1.5 or more.

However, 22π/wavelength and a are easy to use as a diaphragm.

This is called the dimple effect, and is the biggest drawback of cone-shaped diaphragms.

It is easily known that when a flat diaphragm vibrates with a piston at a constant acceleration, a constant sound pressure is obtained on the front axis regardless of the frequency.

For the reasons mentioned above, a speaker as shown in FIG. 3 with a flat diaphragm is used.

3 is a flat diaphragm, 4 is a voice coil for driving it, 5 is a bobbin 1.6 is an edge that supports the diaphragm, 7 is a magnetic circuit, and 8 is a frame.

By employing a flat diaphragm as shown in FIG. 3, the axial sound pressure characteristics become flat in the range where the diaphragm moves in unison.

However, the plane diaphragm is extremely prone to bending vibration, and even if a material with high bending strength is used, it is not possible to obtain the target reproduction band.

For example, the n-th divided vibration frequency fn of a peripherally free diaphragm is calculated using the following formula.

Here, a is the diaphragm, h is the diaphragm thickness, E is Young's modulus, and ρ is the density.

ν is Poisson's ratio, and if ν = 0.33, then 21 =
9.084, λ22=38.55, λ3=87.80
etc.

It is one of the materials with the largest resistance in diaphragms for bass speakers... using Nikum vibration static, fn, n = 1
．． 2. Calculate 3.

a=10m b=0.5cm νρ1,=2 X 10
If crj7's e c2, then f 1 = 984 stops, f2 = 4176 ratio, and f3 = 9511 Hz.

For a diaphragm with a diameter equivalent to 25 cm (a = 10 crn), 984 Hz is within the usable band, and some method must be used to prevent this split vibration from occurring.

f2 is 4176 hz, which is outside the usable band, but in reality, if an edge or voice coil is added to the diaphragm, the calculated value may drop to about 50 coefficients, and the second divided vibration may also be affected by some method. It is desirable to remove it.

The purpose of the present invention is to eliminate second-order split vibrations.

An embodiment of the present invention is shown in FIG.

The difference from the conventional embodiment (Fig. 3) is that a bobbin 25' is added, and the diameters of the bobbin 15 and bobbin 25' on the diaphragm side are equal to the two nodes of the second-order divided vibration of the diaphragm. The diameter of each is the same.

Other details are the same as in Figure 3, so explanations will be omitted.

One end of the bobbin 25' is fixed to the outer peripheral surface of the intermediate portion of the bobbin 15 with an adhesive, and the other end, like the bobbin 15, is fixed to the diaphragm 3 with an adhesive or the like.

Since the plane diaphragm is driven at the nodes of the second-order divided vibration, no second-order divided vibration occurs.

Furthermore, since the two bobbins 5 and 5' coupled to each other drive the inside and outside of the node of the first-order divided vibration mode, the first-order mode is hardly generated.

As described above, in the embodiment of the present invention, the primary and secondary divided vibration modes hardly occur, so that the reproduction band can be significantly expanded compared to the conventional flat speaker.

Furthermore, the tertiary mode occurs at a frequency of 9 KHz or more, but even if it is lowered by 50 factors due to the addition of edges, voice coils, bobbins, etc., it will still be 4 KHz or more, which is sufficient for the reproduction band of a bass speaker.

The above explanation uses bass speakers as an example, but
The same holds true for medium or high-pitched speakers.

As described above, according to the present invention, it is possible to suppress or prevent the split vibration of the primary and secondary vibrations, and it is possible to achieve more faithful reproduction.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a cone-shaped diaphragm in an infinite baffle, Figure 2 is a sound pressure %a diagram when the diaphragm in Figure 1 moves with uniform acceleration, and Figure 3 is a conventional flat plate speaker. FIG. 4 shows a cross-sectional view of an embodiment of the flat speaker according to the present invention. In the figure, 3 is a diaphragm, 4 is a voice coil, and 5.5'
is a bobbin. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] In a speaker having a circular plane diaphragm, the bobbin has a shape that is a combination of a cylindrical shape and a cone shape in parallel, or a bobbin that has a shape that has both cone shapes combined in parallel.The diameter of the bobbin is 1J4IJ.
A flat plate speaker, characterized in that a voice coil is provided on all sides, and the large diameter end side is fixed to each node of the second-order divided vibration mode of the circular flat diaphragm.