| 摘要 |
In an electromagnetic induction type speaker apparatus, individual constants are set in such a manner that the following formula is satisfied Nx(R1xR2)½/(2pixL1x(1-k2)½)>=20000 where R1 is the DC resistance of a primary coil 15: L1 is the inductance of the primary coil 15; N is the number of turns of the primary coil 15; R2 is the DC resistance of the secondary coil 18; L2 is the inductance of the secondary coil 18; and k is the coupling coefficient of the primary coil 15 and the secondary coil 18. In addition, the constants L1 and L2 are selected in such a manner that the ratio of the inductance L1 and the inductance L2 becomes equal to the ratio of the DC resistance R1 and the DC resistance R2.
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