JPH0221838Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electrodynamic speaker, and is intended to achieve high input resistance and high sound pressure sensitivity in a high frequency speaker that requires a small diameter diaphragm.

Recent advances in transistors have made it easy to obtain high-output amplifiers, and a new field of music using synthesizers has also been created.In particular, speakers with high frequency range are now able to withstand high input and output. requested. However, the heat generated by the voice coil determines the limit of a speaker's input resistance, and there is a risk that the coil will burn out if a large input is applied. Therefore, it is necessary to suppress the rise in temperature of the voice coil. As shown in Figure 1, which shows the relationship between voice coil diameter D _P and total thermal resistance R _T , as voice coil diameter D _P becomes smaller,
R _T becomes larger. That is, the voice coil diameter D _P
If is small, this indicates that even a small input will cause a large temperature rise because heat will not escape. Therefore, in order to design a speaker with high input resistance, it is necessary to increase the voice coil diameter.

Figure 2a shows the magnetic permeance (P _g , P _f1 , P _f2 , P _f3 , P _ln ,
P _fp1 , P _fp2 , P _y ). Furthermore, the cross sections of yoke A2, yoke A3, and center pole 4 S _YA , S _YB , S _P
By defining the magnetic permeability μ _YA , μ _YB , μ _P of the magnetic yoke for the total magnetic flux φ _YA , φ _YB , φ _P passing through, the magnetic permeance P _YA , P _YB , P _P of each part of the magnetic yoke can be found. .
If a magnetic equivalent circuit is set using these magnetic permeances, it will be approximately as shown in FIG. 2b. In an electrodynamic speaker, when a signal voltage is applied to a voice coil of length l, the current i flows and the magnetic flux generated in the magnetic air gap.
The force F=B _g l _i is generated by B _g and is used as a driving force to the speaker diaphragm. The above-mentioned magnetic space refers to the narrow portion sandwiched between the yoke A2 and the center pole 4.
In other words, P _g corresponds to magnetic permeance. In the magnetic equivalent circuit shown in Figure 2b, if magnetic flux is made to correspond to current and magnetic permeance is made to correspond to the reciprocal of resistance (conductance), it is clear that in order to concentrate magnetic flux at P _g , P _f1 , P _f2 , P _{+ 3} ,
P _ln , P _y , P _fp1 , P _fp2 are as small as possible, P _g ,
It is desirable that P _YA , P _YB , and P _p be as large as possible.
However, when the voice coil diameter is small, that is, when the diameter of the magnetic air is small, the cross-sectional areas S _p and S _pY of the center pole 4 and yoke A2 become small.
(This is proportional to the square of the aperture). At this time, in order to make the total magnetic flux flowing to P _g constant, it is necessary to make the magnetic flux passing through P _YA and P _p constant, but because the cross section becomes smaller, the yoke within yoke A2 and center pole 4 is The magnetic flux density increases, and for this reason, as shown in Figure 3, when the magnetic permeability of SS ₄₁ yoke, which is generally used as a yoke material, is 14K Gauss or more, it becomes extremely small. Since P _p , P _YA , and P _YB are proportional to this decrease in magnetic permeability, it is undesirable to increase the magnetic flux flowing through the initial P _g . In particular, in high-frequency speakers, the above phenomenon is noticeable because the diaphragm diameter (determined from the diaphragm diameter and reproduction band) is small and the voice coil diameter is inevitably small.

Furthermore, as mentioned above, the output sound pressure sensitivity of an electrodynamic speaker is proportional to F = B _g l _i and inversely proportional to the weight of the vibration system, but when trying to increase the output sound pressure sensitivity, the weight of the vibration system must be reduced. Alternatively, it is required to increase B _g and l. For this purpose, the magnet is made larger, but as mentioned above, if the B _g exceeds a certain level, the desired B _g cannot be obtained when the voice coil diameter is small. When the diameter is increased, the cross-sectional area of center pole 4 and yaw A2 increases in proportion to the square of the diameter.
As P _YA and P _p become larger, a desired magnetic flux density B _g can be obtained, and it is also possible to obtain a larger B _g than when the diameter is small. Moreover, since the diameter is large, when the direct current resistance of the voice coil is constant, a wire with a thicker wire diameter can be used, and therefore the voice coil wire length L can also be increased. This contribution to the output sound pressure sensitivity is primarily determined and the increase in sound pressure is large. In addition, the weight of the vibration system increases due to the increase in wire length, but this does not result in a significant reduction in sound pressure due to the relationship with the weight ratio with components other than the voice coil, such as the diaphragm. Therefore, output sound pressure sensitivity can be increased.

As mentioned above, it has been shown that high input resistance and high output can be obtained by increasing the voice coil diameter, but the acoustic radiation diameter of a high-frequency speaker is determined by the frequency range handled by the speaker system and cannot be changed freely. It was hot.

FIGS. 4 and 5 show cross-sectional views of conventional electrodynamic speakers. The magnetic circuit section consists of a magnet 1, a fork A2, a yoke B3, and a center pole 4.
A voice coil 5 wound around a voice coil bobbin 6 is suspended by an edge 7 in the magnetic air. 8 is a dome-shaped diaphragm provided at the upper end of the voice coil bobbin 6. Note that 9 is Edge 7
Supporting material for fixing the other end to the magnetic circuit section, 1
0 is a sound absorbing material inserted between the dome-shaped diaphragm 8 and the upper surface of the center pole 4. Further, FIG. 5 shows an electrodynamic speaker in which the upper part of a dome-shaped diaphragm 8 is filled with foamed resin 1 and the surface thereof is made flat.

In the conventional electrodynamic speaker described above, the diameter of the dome-shaped diaphragm 8 and the diameter of the voice coil 5 are equal;
As mentioned above, it has been difficult to increase both the input resistance characteristics and the output sound pressure level.

To explain in detail using specific numerical values, it is generally desired that the diameter of the diaphragm of a high-frequency speaker satisfies the following equation at a maximum audible frequency of 20 kHz, taking into account its directivity.

2πf/c·a<3 Here, f is the frequency, c is the speed of sound, and a is the radius of the diaphragm. When the allowable diameter b=2a of the diaphragm is calculated by modifying the above equation based on f=20 kHz and sound speed c=340 m/sec, it becomes b≒16 mm. That is, a diaphragm diameter of 16 mm is the maximum allowable size. Therefore, in conventional designs, the voice coil diameter had to be smaller than this. However, under this restriction, it is very disadvantageous to increase the input resistance and the magnetic flux density of the magnetic gap as described above. In particular, with regard to magnetic flux density, no matter how much the amount of magnets is increased, there is almost no effect, and highly efficient conversion cannot be performed.

This invention solves the above-mentioned conventional problems, and makes it possible to install a large-diameter voice coil on a small-diameter diaphragm. It provides a type speaker. An embodiment of the present invention will be described below based on the drawings.

6, 7, and 8 are sectional views showing embodiments of the present invention, and the same members as in the conventional example are given the same numbers and detailed explanations are omitted.

A feature of this embodiment is a cone-shaped connector 12, which is integrated with the voice coil bobbin in the illustrated embodiment. That is, a dome-shaped diaphragm 8 (the diameter is the same as that of the conventional example) is connected to the upper end of the cone-shaped connector 12, and the lower end of this cone-shaped connector 12 is larger than the aperture (inner diameter of the edge) of the dome-shaped diaphragm 8. It has a large diameter and a voice coil 5' is wound around its lower end. According to this embodiment configured as described above, the lower end has a diameter larger than the diameter of the upper end of the cone-shaped connecting member 12, and the dome-shaped diaphragm 8 is wound around the upper end and the voice coil is wound around the outer periphery of the lower end. Since it is rotated, high frequency characteristics due to the effective acoustic radiation aperture remain the same, high input resistance characteristics can be achieved, and high output sound pressure level characteristics can be obtained.

The embodiment shown in FIG. 7 corresponds to the conventional example shown in FIG. 5, and the dome-shaped diaphragm 8 of the embodiment shown in FIG.
The upper part is filled with foamed resin 11.
Further, with this shape, a configuration as shown in FIG. 8 is also possible.

In this case as well, substantially the same effect as the embodiment shown in FIG. 6 can be obtained. In each of the above embodiments, the cone-shaped connecting member 12 integrated with the voice coil bobbin was used, but as shown in FIG. It is also possible to have a structure in which the dome-shaped diaphragm 8 having a small diameter is adhesively connected with a separate cone-shaped connecting member 12'.

As described above, according to the present invention, the diameter of the voice coil bobbin is made larger than the diameter of the diaphragm, and the voice coil bobbin and the diaphragm are connected by a connecting member. It is possible to realize high input resistance and high output while maintaining the characteristics, and it is possible to realize a practical high-frequency electrodynamic speaker with a wide range of applications.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the voice coil diameter and total thermal resistance, Figure 2 a and b are the configuration diagram of the magnetic circuit section and its equivalent circuit diagram, and Figure 3 is the relationship between magnetic flux density and magnetic permeability. Figures 4 and 5 are cross-sectional diagrams showing conventional electrodynamic speakers, Figures 6 and 7,
FIG. 8 is a sectional view showing an embodiment of the present invention,
FIG. 9 is a cross-sectional view of the main part of another embodiment. 5'...Voice coil, 6'...Voice coil bobbin, 7...Edge, 8...Dome-shaped diaphragm, 1
2'... Cone-shaped connection.

Claims (1)

[Claims for Utility Model Registration] (1) The diameter of the voice coil bobbin that transmits the driving force induced by the current applied to the voice coil is larger than the diameter of the diaphragm, and the voice coil bobbin and the diaphragm are connected to each other. , a high-frequency electrodynamic speaker characterized by being connected by a cone-shaped connecting member. (2) A high-frequency electrodynamic speaker according to claim 1, characterized in that a voice coil bobbin and a cone-shaped connecting member are integrally formed. (3) The diaphragm has a front chamber formed by a dome-shaped diaphragm, a plane including the front surface of the frame, and a cylindrical surface including the inner peripheral edge of the frame, and this front chamber is filled with foamed resin. A high-frequency electrodynamic speaker according to claim 1 of the utility model registration claim.