| 摘要 |
PURPOSE:To attain excellent electro-acoustic converting efficiency and inexpensive cost from the standpoint of cost by fitting a cylindrical voice coil freely to the upper side face of a center pole and connecting this cylindrical voice coil and the ring shaped voice coil. CONSTITUTION:When the ring shaped voice coil 4 and the cylindrical voice coil 7 are driven in the same direction by applying a drive current to the ring shaped voice coil 4 and the cylindrical voice coil 7, a large acoustic output is obtained because the vibrating amplitude of the cylindrical voice coil 7 having a comparatively large vibrating amplitude is added to the vibrating amplitude of the ring shaped voice coil 4. Further, when the direction of the ring shaped voice coil 4 driven is opposite to the direction of the cylindrical voice coil 7 driven, the generation of an unnecessary peak on the acoustic output is prevented because the large vibration in opposite direction of the cylindrical voice coil 7 is damped by the ring shaped voice coil 4. |
