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JPS57196696

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DESCRIPTION JPS57196696
Description 1, title of the invention
Electrodynamic speaker
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodynamic
loudspeaker using permanent magnets in a magnetic circuit. In such a speaker, generally, a
conductor of a vibration system is disposed in a magnetic gap of a magnetic circuit, and a force
corresponding to the current direction and size is generated by a sound current flowing through
the conductor to vibrate the diaphragm. It is configured to let you In order to cause this vibration
efficiently, it is preferable to select an operating point at a point M at which the B11 product on
the B-H characteristic curve of the permanent magnet becomes maximum as shown in FIG.
However, in practice, when an AC magnetic flux generated by flowing a voice current through a
conductor and a DC magnetic flux generated by a permanent magnet are superimposed, when
the operating point is set at the above-mentioned m point, the superposed magnetic flux The
operating point is due to the B-H curve of FIG. 1! As it enters the region, irreversible
demagnetization occurs in the permanent magnet. Therefore, to cause such an occurrence, the
efficiency is lowered but the KP region is operated as shown in FIG. 2 with a margin. Even in this
case, however, the operating point moves in accordance with the polarity and magnitude of the
audio current applied to the conductor, and the magnetic flux density changes in the range
shown by 0 in FIG. 2 along with EndPage: 1. Become. When such a change occurs in the linear
portion of the B-1 curve, third harmonic distortion occurs, and when it occurs in the curved
portion, tI / E2 harmonic distortion also occurs. In addition, if there is not enough room for
operation in the P area, as shown in Fig. 4, the large audio current is input) and the operating
point reaches the I area so that demagnetization occurs. become. Until now, the above
phenomena were either left unchecked or, at most once, drastic measures were not taken at all
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once suppressed by the caustic-triling. The present invention has been made in view of the
above-described points, and its object is to suppress the occurrence of distortion by suppressing
the fluctuation of the operating point of the magnetic circuit due to the magnetic field generated
by the conductor of the vibration system. An object of the present invention is to provide an
electrodynamic speaker. The present invention will now be described with reference to FIGS. 4 to
7 of the drawings. FIG. 4 is a partially broken view showing an example of the basic configuration
of the electrodynamic speaker according to the present invention. In the figure, 1 is a permanent
magnet, 2 is a pack having a center pole 2 turtle at the center, Cgrate, 3 is a top plate, and these
are external magnet types that form a magnetic sky ysa at the opposing portion of the top plate 3
and the center ball 21 The magnetic circuit of Further, 4 is a povin, 5 is a voice coil wound
around the povin 4,-is a diaphragm, T is a damper, and these constitute a vibration system of the
speaker.
The voice coil 5 which is a conductor of the vibration system is disposed in the magnetic space
11G together with the povin 4 and a voice signal current is supplied to the voice coil 5 as well as
the voice signal source 8 through the lead wire S. The above magnetic circuit ok? An excitation
coil is wound on the tar pole 2 &, and an audio signal current is supplied to the excitation coil via
the lead wire 10 as well as the audio signal source 8. As shown in the above-mentioned exciting
coil 9i, 111, a magnetic flux ? generated by the voice coil sK. The magnetic flux ? is provided
so as to generate a substantially large magnetic flux ? only in the opposite phase of the phase.
However, the size of the magnetic flux ? is adjusted by a variable resistor inserted into one of
the lead wires 10 be able to. As described above, by configuring the speaker), in particular, an
alternating current flux generated mainly by a voice coil portion that protrudes from a magnetic
gap in a four-ring voice coil lllID speaker and a direct current flux generated by a permanent
magnet Since the magnetic flux fluctuation caused by the superposition is canceled and a
constant magnetic flux density can be obtained at all times, the occurrence of distortion,
demagnetization, etc. occurring during the fluctuation of the operating point of the magnetic
circuit caused by the conventional speaker is suppressed. It will be By the way, the voice coil
impedance (?) of an actual speaker has a peak at the peripheral fluid number f0 as shown in
FIG. 6, and the p impedance in the high region has a rise in tie impedance due to the inductance
of the voice coil. This rounding, the voice current flowing in the voice noise part becomes
different depending on the number of peripheral fluid even when the applied voltage is constant.
On the other hand, since the magnetic flux fluctuation is blocked due to the current, it is
necessary to adjust the voice current applied to the exciting coil port for cancellation as well to
an optimum value according to the frequency. EndPage: 2 Fig. 1 shows an example of an actual
circuit that enables the adjustment as described above, exciting the audio signal source S;
inductors connected in parallel to each other on one of the lead wires connected to the coil 9 A
series circuit of L1 capacitor 10, resistor R and variable resistor R is inserted. The inductor b and
the capacitor 0 are set such that the number of resonance fluids is t и, and q of the resonance
circuit consisting of the resistors 1 tiL and 0 is set. This is for adjusting the magnitude of the
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audio current flowing through the variable resistance product vR excitation coil 8. As described
above, the combination of the excitation coil $ and the value 0 combination of O, R and RR is
appropriately set: иии 1: proportional to the voice current applied to the voice coil S It becomes
possible to cause the voice coil current to flow to the exciting coil 9, and it becomes possible to
obtain a KxL-preferred flux fluctuation canceling effect regardless of the frequency plate of the
voice signal.
Among them, in the above-described embodiment, an example of the magnetic circuit of the
outer magnetic water is shown, but the present invention is not to mention the magnetic circuit
of the inner magnetic type, but it is of course provided with a permanent magnet! ?? It is
equally applicable to nine speakers using magnetic circuits. In the above embodiment, the
exciting coil is wound around the center ball, but at a position such as the outside of the
permanent magnet which excites the permanent magnet and generates a magnetic flux which
may affect the magnetic flux in the air gap of the magnetic circuit It is needless to say that it may
be provided on a pot if it is. The present invention is also applicable to a ribbon ? ? ? ?
speaker in which the conductor of the vibration system is caught with the vibration body. As
described above, according to the present invention, in the exciting coil provided in the magnetic
circuit, the conductor of the vibration system does not reach the application of the audio current
to the e1m circuit and excites the magnetic circuit in reverse to the exciting action. A current
according to the magnitude is applied. Therefore, the fluctuation of the magnetic circuit Oa flux
due to the magnetic flux generated by the conductor of the vibration system is canceled out, and
a constant magnetic flux density can be always obtained, the fluctuation of the operating point of
the permanent magnet is suppressed, and the generation of distortion accompanying the
magnetic flux change Will be prevented. Since it is possible to eliminate the demagnetization of
the permanent magnet at the time of p large input for the same reason, there is no need to look
into the margin for infallibility, and choose an operating point larger than p ? = JII product O It
is possible to improve the utilization efficiency of the magnet, improve the performance, and
obtain an electrodynamic loudspeaker with a cost-averaged performance.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph for explaining the problems of the
conventional electrodynamic speaker, FIG. 4 is a partially cutaway view showing the basic
configuration of the electrodynamic speaker according to the present invention, Fig. 1II is a
partial cross-sectional view of the rounding explaining the operating principle of Subi i in Fig. 4,
Fig. 1 is a graph showing the wave plate-in-impedance characteristics of the voice coil, and Fig. 1
is a circuit diagram showing one embodiment. ? -j1: permanent magnet, S: dice coil #
(conductor)-: excitation coil, S: sound signal source. Patent Applicant Pioneer Corporation
EndPage: ?
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