| 摘要 |
The loudspeaker system includes a loudspeaker drive unit (2) and a tube (4) acoustically coupled to the rear of the loudspeaker drive unit for leading away and absorbing sound waves produced at the rear of the loudspeaker drive unit. The tube is acoustically coupled to the loudspeaker drive unit by a hollow resonant enclosure (6) and the loudspeaker drive unit is mounted at an aperture (8) in an external wall of the enclosure. The tube communicates with the interior of the enclosure and extends outwardly from the enclosure. There is a significant change in acoustic impedance where the tube communicates with the interior of the enclosure. The fundamental resonant frequencies of the enclosure and the tube each lie between the first and second frequencies but the Helmholtz resonant frequency of the tube, when its distal end is open, lies below the first frequency. The effect of the enclosure is to "short circuit" sound at the frequencies of the higher order resonances of the tube so that those resonances are not excited to any significant extent. |
