| 摘要 |
PURPOSE:To decrease the minimum resonant frequency without lowering the efficiency at the band in use, by coupling the drive section and a diaphragm plate acoustically or via mechanical filter to produce a resonant frequency in a given band. CONSTITUTION:A mechanical filter 11 is made of a mechanical elastic material such as rubber and spring. A bobbin 5 and a diaphragm plate 9 are coupled via this mechanical filter 11. This mechanical filter 11 is made soft and the resonant frequency is made low by making small the compliance, allowing to produce the resonant frequency in a given band. Further, when frequency of sound frequency is of single peak, the driving force is selected so that the efficiency at the resonant frequency is in the range from a maximum to 1/4. |
