PURPOSE: To enable thin structure and to reduce the number of parts by magnetizing magnets connected to each diaphragm respectively provided on one side and on the other side to the same polarity.

CONSTITUTION: A frame 1 is formed by connecting two identical shaped ones formed to reverse circular truncated cone shape with a cylindrical stand member 1a on the bottom and forming them to be in an opening state in the right and the left direction along the identical axial center. On the outer periphery of the stand member 1a of this frame 1, a coil 2 for driving is wound. In the inside of the coil 2 composed of this two winding wires, a bobbin 7 is symmetrically installed through a damper 9 to a center line A, and a columnar or annular magnet 5 is provided as a movable magnet at a position respectively corresponding to a first and a second winding wires of the coil 2 on the outer peripheral surface of these bobbins 7. The magnets 5 equipped with the bobbins 7 on both sides are arranged to be the same polarity. A diaphragm 3 is fixed in the opposite end part arranged the magnets 5 of such bobbins 7.