| 摘要 |
PURPOSE:To make the acoustic pressure frequency characteristic flat and to reduce the nonlinear distortion by feeding back oscillation system displacement information of a speaker, which is detected by a laser light interferometer, to a driving system of the speaker. CONSTITUTION:Displacement information of a diaphragm detected by a photodetector 7 of the laser light interferometer is supplied to a preamplifier 11 and a comparing circuit 12 for waveform shaping, and this output is supplied to an up/down counter 13 together with the output of a direction discriminating circuit 14. The output signal from the counter 13 is converted to an analog signal by a D/A converter 15 and is supplied to a differential amplifier 16. The digital audio signal supplied to an input terminal 17 is converted to an analog signal by a D/A converter 18 and is compared with a reference voltage passing through a sound band limiting filter 19. The comparison error signal from the differential amplifier 16 is supplied to a driving coil 8 through a phase compensating filter 20 and a driving circuit 21 of the speaker. |
