| 摘要 |
PURPOSE:To lower the sound pressure level at the minimum resonance frequency, by coupling a dust cap which is more than half the mass of the vibrating system excluding the dust cap with the upper part of the diaphragm or the voice coil with some elasticity. CONSTITUTION:A magnetic circuit 13 is constituted by piling up a plate 15 having a center pole 14, a ring-shaped magnet 16, and a ring-shaped upper plate 17 in the described order, and a frame 18 having no window is coupled with the magnetic circuit 13. To the rim part of the frame 18, a cone-shaped diaphragm 20 is glued together with a gasket 19. The central part of the diaphragm 20 is coupled with a voice coil 21 supported by a dumper 22. Moreover, with the upper surface of the center of the diaphragm 20, a dome-shaped dust cap 24 which is more than half the mass of the vibrating system composed of the diaphragm 20, the voice coil 21, and the dumper 22, is coupled. In this way, the sound pressure level at the low band resonance can be controlled with a simple structure. |
