| 摘要 |
PURPOSE:To enable to keep constant filter frequency for a long time by preventing the air held in the part surrounded by the elastic material combining a diaphragm with a voice coil bobbin and a dust cap from leakage. CONSTITUTION:When the upper end of voice coil bobbin 4 is closed with cap 12, the air held in the part surrounded by diaphragm 6, bobbin 4, dumpter 9, dust cover 11, and cap 12 is sealed up. Since air compliance (COMP) has no relation to the fatigue of dumper 9 at the time, the filter frequency decided by the weight of air COMP and diaphragm 6 and the weight of bottin 4 is not changed also by the fatigue of dumper 9 and, therefore, constant filter frequency can be kept up for a long time. In addition, the minumum resonance frequency of the speaker can be prevented from being increased by applying transparent hold 4a to the periphery of bobbin 4. |
