To prevent deterioration in reproduced sound quality by preventing deterioration in an electromagnetic coupling force of an electromagnetic speaker so as to reduce production of an electromagnetic wave due to a harmonic component in the case that a primary coil of the electromagnetic speaker is driven by a digital audio signal.
A primary coil of a speaker unit 10 of an electromagnetic speaker is made up of 16 coils 1A-1Q, and current sources 65A-65Q whose peak currents are Ia-Iq are connected to the coils 1A-1Q via current control circuits 66A-66Q. A chopper 230 is used to set an inactive period for each sampling period to each bit signal of an input digital audio signal Dp being a natural binary code. Each bit being an output of the chipper 230 is fed to a low pass filter 240 and a harmonic component in each bit signal is reduced and each bit signal with a smooth waveform is fed to the current control circuits 66A-66Q.
| JP2023542415 | Speaker and terminal |
| JPS61139194 | DYNAMIC LOUDSPEAKER |
KISHIGAMI JUN
FUJIHIRA MASAO
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