| 摘要 |
PURPOSE:To eliminate reflection sound at a listening point by providing a sub- woofer in addition to a main woofer being a cause to generation of reflection sound and taking the phase of the reflecting sound from the main speaker inverse to the direct sound from the sub-woofer. CONSTITUTION:There is not phase shift in a signal fed to the main woofer 4 and the sub-woofer 5 via LPF7, 8 at a low frequency smaller than a frequency fa and the woofers 4, 5 are operated in parallel. When the frequency is increased and reaches the fa, the phase of the signal fed to the LPF8 is shifted by 180 deg. and the phase is opposite to that of the output of the LPF7. Thus, the low frequency range generated from the main speaker 4 and the sub-woofer 5 is opposite in phase to each other, the direct sound from the woofer 5 and the reflected sound from the woofer 4 are cancelled together at the listening point LP, thereby giving the same effect that no reflecting sound reaches the listening point LP. |
