| 摘要 |
PURPOSE:To achieve the reduction of depth size without impairing sound quality by providing a magnetic circuit comprising providing the magnetic poles of permanent magnets placed close to the four long planes of a voice coil to a voice coil and series-constituting. CONSTITUTION:A coupler 12 is fixed to the center of one outside end long face 11a of the outside circumference part of an approximately rectangular and hollow coil. The outside circumferential parts of a cone 13 and damper are fixed to a frame 15, hence the voice coil is oscillatably supported in the arrow A direction. There are four permanent magnets 16 making face contact in proximity to the four long planes 11b existing in the voice coil and the directions of magnetization thereof are perpendicular to the long plane of the coil, these four magnets forming the series magnetic circuit sandwiching the longer sides of the voice coil with two yokes 17. Thereby, the depth size may be reduced without imparing sound quality because of the thin type construction or the like. |
