JPH0124478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodynamic electroacoustic transducer comprising a flat coil diaphragm sandwiched between a pair of flat magnets.

Generally, as shown in FIG. 1, this type of electroacoustic transducer has flat magnets 2, 2 having a plurality of sound holes 1 formed therein, with their repulsive surfaces facing each other with a predetermined gap between them. It is constructed by sandwiching a planar coil diaphragm 3 made of a spirally wound coil between them via electrically insulating spacers 4 arranged at the center and circumference of the magnets 2, 2. There is. However, such a conventional electroacoustic transducer has a drawback of poor frequency characteristics in the high frequency range, as shown by the solid line in the sound pressure frequency characteristic diagram of FIG. This is because when transmitting the vibration generated in the gap between the magnets 2 through the sound hole 1, the viscous resistance of the air increases, especially in the high frequency range, resulting in over-damping of the vibration system. In order to avoid this over-braking, it is sufficient that the sound holes 1 are acoustically sufficiently opened, but if the number and area of the sound holes 1 are simply increased, the acoustics will be satisfied. Since the effective area of the magnets 2, 2 decreases, the sensitivity decreases and the transducer cannot exhibit its performance.

The present invention has been made in view of these points, and its object is to provide an electroacoustic transducer with excellent high frequency characteristics and high sensitivity without impairing the effective area of the magnet.

The present invention will now be described in detail with reference to the embodiments shown in FIGS. 3 and 4. In addition,
In these figures, the same parts as in FIG. 1 are given the same reference numerals.

As shown in FIG. 3, this electroacoustic transducer includes a pair of magnets 5, 5 that are arranged parallel to each other with a spacer 4 made of an electrically insulating material in between so as to create a certain gap. We are prepared. A planar coil diaphragm 3, which is formed by winding a coil on an electrically insulating thin film, is held in parallel between the magnets 5, 5 by the spacer 4. Each of the above-mentioned magnets 5 is composed of a disc body having a predetermined thickness and whose center portion and outer circumferential portion are magnetized with different polarities, and a plurality of sound holes 1 are bored in this disc body. There is. In this case, the surface of each magnet 5 facing the planar coil diaphragm 3 has a plurality of grooves 6 extending radially from the center toward the outer periphery, as illustrated in FIG.
is provided. In this embodiment, groove 6
Although the sound holes 1 do not overlap with the sound holes 1, the number, position, diameter, etc. of the sound holes 1 may be selected depending on design conditions, and the sound holes 1 may be provided so as to overlap with the grooves 6.
Note that reference numeral 7 is an insertion hole for the spacer 4 formed in the magnet 5.

The electroacoustic transducer shown in this embodiment is configured as a speaker that inputs an electric signal to the coil of the planar coil diaphragm 3 located within the magnetic field of the magnets 5, 5, and vibrates the planar coil diaphragm 3 by the electromagnetic force. ing. Therefore, due to the vibration of the planar coil diaphragm 3, air vibration in the gap formed between the two magnets 5, 5 is transmitted from the sound hole 1 to the space outside the electroacoustic transducer. In that case, in this invention, as described above, since the groove 6 is provided on the opposing surfaces of the magnets 5, 5, the volume of the gap between the magnets 5, 5 increases, and the planar coil diaphragm 3 is directly driven. The amount of air that can be produced increases, making it less susceptible to the effects of braking due to viscous resistance of air, and since the grooves 6 are formed radially,
The space along the vibration surface of the planar coil diaphragm 3 is connected in the radial direction, the magnitude of the amplitude of the vibration surface and the phase delay are averaged, and the air in the gap is directed in the direction of lower pressure through the groove 6. The radial release prevents an increase in viscous resistance in the sound hole. In other words, by short-circuiting the vibration diameter of the air in the space via the radial grooves 6 provided on the opposing surfaces of the magnets 5, 5, the increase in viscous resistance in the high frequency range is suppressed and the vibration of the electroacoustic transducer is suppressed. Over-braking of the system can be effectively prevented. This ideally improves the response of the electroacoustic transducer in the high frequency range. The results of this response improvement are shown by broken lines in FIG. According to the sound pressure frequency characteristics of this invention shown by this broken line, the response is flat up to about 20kHz, which is the limit of human hearing, which is difficult to do with conventional electroacoustic transducers whose response degrades from around 3kHz. High fidelity reproduction is possible with this invention.

Although this embodiment describes a planar drive speaker using a planar coil diaphragm, it goes without saying that the present invention is also effective for planar drive microphones based on the same principle.

As described above, according to the present invention, in a planar electroacoustic transducer using a perforated magnet, radial grooves are provided on the surface of the perforated magnet on the side facing the diaphragm. It is possible to provide an electroacoustic transducer with good sensitivity and excellent high-frequency characteristics without impairing the effective area of the transducer.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a conventional planar drive type electroacoustic transducer, FIG. 2 is a sound pressure frequency characteristic diagram of the conventional example and the electroacoustic transducer according to the present invention, and FIG. 3 is a diagram of the sound pressure frequency characteristics of the electroacoustic transducer according to the present invention. A partial cross-sectional view of the electroacoustic transducer, FIG. 4 is a perspective view of the magnet shown in FIG. In the figure, 1 is a sound hole, 2 and 2 are conventional magnets,
3 is a planar coil diaphragm, 4 is a spacer, 5 is a magnet according to the present invention, and 6 is a groove.

Claims (1)

[Claims] 1. A pair of flat perforated magnets are opposed to each other at a constant interval in a state where they repel each other, and a flat coil diaphragm formed by spirally wound coils is arranged parallel to the magnets. 1. An electroacoustic transducer characterized in that a plurality of radially expanding grooves are provided on a surface of the flat perforated magnet facing the planar coil diaphragm.