| 摘要 |
PURPOSE:To protect a speaker at the time of large input by detecting the vibration of the speaker and controlling the gain of a feedback circuit with a subsidiary signal to an input signal. CONSTITUTION:The reproducing sound reproduced from a speaker 2 is detected by a microphone 5, amplified by a microphone amplifier 6 and converted to a signal for control through a signal converting part 7. At a feedback circuit 8, a gain of an acceleratin signal is adjusted, applied to the inverting input of an adding part 9 and added to the input signal, in accordance with the signal for control from a control means 4. When a fly-back quantity is increased, the resonance frequency of a low band resonance system is lowered, Q0 is increased, and the level of a low band resonance frequency or above is decreased. Thus, by controlling the gain of the feedback circuit 8 in accordance with the reproducing sound level, the correction of the frequency characteristic in accordance with the reprodcing sound level, the decreasing of distortion at the time of the large input and the protection of the speaker can be attained. |
