| 摘要 |
PURPOSE:To eliminate a collision of back plate for a voice coil bobbin and realize a reproduction with no distortion, by sealing up the upper and part of said bobbin and at the same time providing a vent at the position which is within a plate when the bobbin has a large amplitude. CONSTITUTION:A vent 14 is formed at the area very close to the voice coil 10 of the voice coil bobbin 9. When the bobbin 9 has a large swing downward at the time of a big input, the vent 14 goes into the lower part of a very narrow gap 12 for an instant to reduce greatly the compliance of the air room 15. As a result, the down amplitude of the bobbin 9 is suppressed greatly to avoid completely a collision between the bobbin 9 and the back plate 1. In this case, an abnormal sound or the like defect can be eliminated completely. A distortionless vibration is secured as conventional at the time of an ordinary input. Thus an excellent reproduction is always secured with no distortion at all. |
