JPS6231878B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrodynamic planar drive speaker, and more particularly to an electrodynamic planar drive speaker that directly reproduces a pulse code modulated signal as an acoustic signal. So-called pulse code modulation (hereinafter referred to as PCM), which pulse-codes an acoustic signal and transmits or records and plays it back.
This method has many advantages, such as being resistant to distortion and noise, having a large dynamic range, being unaffected by the performance of the transmission line or recording system, and being suitable for multiplexing. Conventionally, in order to reproduce this PCM signal as an audio signal, after performing digital/analog conversion,
Since the audio signal was reproduced by supplying an analog signal to a speaker, it had the disadvantage that it was greatly affected by noise generated by the digital/analog converter at the final stage of the system. The present invention provides a speaker that can directly convert a PCM signal into an acoustic signal without digital/analog conversion, and furthermore, by configuring this type of speaker as an electrodynamic planar drive speaker, This made it possible to implement the project. Before describing embodiments of the present invention, an electrodynamic planar drive speaker will first be described. Figure 1 shows a general electrodynamic flat speaker.
4 is a wire conductor 5 on a flexible resin film.
The diaphragms 6 and 7 are permanent magnets arranged with a slight gap from the diaphragm, and the magnetic pole faces adjacent to the diaphragm are arranged to have alternately different polarities. The linear conductor 5 is printed between adjacent magnetic poles on the resin film by photo-etching or by a printing process using conductive printing ink in a manner similar to that used for printed wiring boards. The linear conductor 5 is formed in a zigzag shape having parallel conductor portions, as shown in FIG. 8 and 9 are yokes, and an acoustic hole 10 is provided between the magnetic poles of the yoke 8. The broken line indicates the distribution state of magnetic flux. As mentioned above, compared to an electrodynamic speaker with a wire-wound coil, in an electrodynamic planar drive speaker, the linear conductor can be formed by print molding, so the length, width, or pattern of the conductor can be arbitrarily determined. There are features that allow it. The present invention utilizes the features of the electrodynamic planar drive speaker described above to provide a speaker for reproducing PCM signals. Hereinafter, embodiments according to the present invention will be described. FIG. 3 shows a pattern of a linear conductor in an embodiment of the present invention, in which 1 is a linear conductor having terminals 1a and 1b, 2 is a linear conductor having terminals 2a and 2b,
3 is a linear conductor having terminals 3a and 3b. The width of each linear conductor is the same, and the lengths of the linear conductors 2 and 3 are twice and four times that of the linear conductor 1, respectively. The diaphragm 2 is assembled in the same manner as the diaphragm of the electrodynamic planar drive speaker described with reference to FIG. Now, when a pulse current of a constant current I is supplied to the wire conductor 1, the driving force F generated in the wire conductor 1 is given as F=BlI (B: magnetic flux density, l: length of the conductor), so A driving force twice and four times the driving force generated in the linear conductor 1 is generated in the linear conductor 2 and the linear conductor 3, respectively. That is, the length of each wire conductor is changed depending on the supplied bit signal to give weight. A pulse current corresponding to the first bit of the PCM signal is applied to the terminals 1a and 1b of the linear conductor 1, and a pulse current corresponding to the second bit is applied to the terminals 2a and 2b of the linear conductor 2. and the wire conductor 3
A pulse current corresponding to the third-order bit is applied to the terminals 3a and 3b. The relationship between the PCM signal and the driving force generated in the linear conductor and the diaphragm where the driving force is generated by the PCM signal is as follows.

[Table] That is, when a PCM signal of "000" is given to each linear conductor, no pulse current flows to any of the linear conductors, so the diaphragm is not driven. When the PCM signal is "001", a pulse current flows only to the wire conductor 1, and a driving force as one unit of analog quantity is obtained to the diaphragm. The pulse signal flows only through the strip conductor 2, and since the strip conductor 2 has twice the length of the strip conductor 1, two units of driving force can be obtained to the diaphragm. Furthermore, when the PCM signal "011" is given to each wire conductor, a pulse signal is given to wire conductors 1 and 2, and a total of 3 units of driving force is obtained to the diaphragm. . In the same way, the analog quantity corresponding to the PCM signal can be converted from digital to analog.
It can be directly reproduced as an acoustic signal. FIG. 4 shows another embodiment of the present invention, in which the lengths of the linear conductors 1, 2, and 3 are the same, and the widths of the linear conductors 2 and 3 are twice and four times the width of the linear conductor 1, respectively. It is formed to be. That is, when a constant pulse voltage corresponding to each bit of the PCM signal is applied to each wire conductor, the pulse current flowing through the wire conductors 2 and 3 is proportional to the width of the wire conductor.
A pulse current twice and four times that of the linear conductor 1 flows, respectively, and a driving force twice and four times as much as that of the linear conductor 1 is obtained, respectively, and the same effect as in the first embodiment is performed. As described above, the present invention is configured to give weight by changing the length or width of each wire conductor depending on the bit signal of the PCM signal, and therefore, it is possible to perform digital/analog conversion. It is possible to directly convert a PCM signal into an acoustic signal without performing any conversion, and it is possible to completely eliminate the effects of noise associated with digital/analog conversion. In the above explanation, 3-bit PCM is used for simplicity.
Although explained as a signal, in reality, 8 to 14 bit pulses are used, so in reality there are 8 to 14 wire conductors, the terminal of each wire conductor, and from this terminal. It is necessary to provide a leader line, etc. Furthermore, the length or width of each wire conductor is
(N is the number of bits of the PCM signal) It is necessary to weight the signals according to the following relationship. According to the present invention, since the PCM reproduction speaker is configured as an electrodynamic planar drive speaker, and the pattern of the linear conductor provided on the diaphragm can be arbitrarily formed by print molding, the electrodynamic speaker having a wire-wound coil can be used. It can be manufactured and implemented easily compared to the configuration as .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a general electrodynamic planar drive speaker, FIG. 2 is a plan view showing the diaphragm in FIG. 1, and FIG. 3 is a pattern of a linear conductor according to an embodiment of the present invention. , FIG. 4 shows another embodiment according to the invention. 1, 2, 3, 5... wire conductor, 4... diaphragm,
6,7...Permanent magnet, 8,9...Yoke, 10...
...acoustic hole.

Claims (1)

[Claims] 1. An electrodynamic planar drive speaker having a diaphragm made of an insulating material having a linear conductor and a plurality of magnetic poles arranged with a slight gap between the diaphragm and the diaphragm,
The linear conductor is composed of a plurality of wires corresponding to the number of bits of the pulse code modulation signal to be supplied, and the width of each of the linear conductors is changed or weighted depending on the bit signal of the pulse code modulation signal. An electrodynamic planar drive speaker characterized by: