| 摘要 |
PROBLEM TO BE SOLVED: To apply large magnetic force to a gap part by improving the utilization efficiency of a magnet and to freely set the diameter of the gap part or amplitude of a diaphragm. SOLUTION: Two center pole parts 152 and 154 are provided for concentrically forming two gap parts 162 and 164. Plural plates 210, 220, 230 and 240 are provided parallel from the respective center pole parts 152 and 154 to an outer diameter direction. The respective plates 210-240 are equipped with driving magnets 310, 320 and 330 and a magnetic field is applied to the respective gap parts 162 and 164. The respective plates 210-240 are equipped with cancel magnets 340, 350 and 360 and a shield cover 250 surrounding a magnetic circuit is provided. Concentric voice coil bobbins 172 and 174 provided on a diaphragm 110 and cap bodies 120A and 120B are inserted and arranged in the respective gap parts 162 and 164 and voice coils 182 and 184 provided in respective bobbins 172 and 174 are driven.
|
