Patent ID: 7065221

Claim:
A speaker apparatus comprising: an amplifier operable to receive an input signal and to output an amplified signal; a speaker unit operable to reproduce the amplified signal and to radiate an acoustic output signal; an acoustic pipe mounted in front of said speaker unit; a microphone disposed in said acoustic pipe, said microphone being operable to detect the acoustic output signal radiated from said speaker unit; and a feedback circuit operable to feed the acoustic output signal detected by said microphone back to an input side of said amplifier; wherein said microphone is placed at a position where sound pressure of resonance occurring in a longitudinal direction, in a latitudinal direction orthogonal to the longitudinal direction, and in a direction orthogonal to both the longitudinal direction and the latitudinal direction of the acoustic pipe is low enough so as not to cause oscillation; and wherein said microphone is placed at a position where sound pressure of a second and third pipe resonance in the longitudinal direction, in the latitudinal direction and in the direction orthogonal to both the longitudinal direction and the latitudinal direction of the acoustic pipe is low enough so as not to cause oscillation, and where sound pressure of a resonance occurring in a closed space of the acoustic pipe is low enough so as not to cause oscillation.