Patent ID: 8422727

Claim:
An electro-acoustical transducer, comprising: a diaphragm of an elongated shape; an edge for supporting the diaphragm such that the diaphragm is vibratable; a first magnet of a parallelepiped shape which is (i) situated at a face of one principal surface of the diaphragm such that long sides of the first magnet are in parallel with long sides of the diaphragm, (ii) polarized in a short side direction of the diaphragm to form a first magnetic gap to a side of the one principal surface of the diaphragm, and (iii) polarized in a direction perpendicular to a vibration direction of the diaphragm; a second magnet of a parallelepiped shape which is (i) situated next to the first magnet in the short side direction of the diaphragm such that long sides of the second magnet are in parallel with the long sides of the diaphragm, (ii) polarized toward a direction in a manner opposite to the first magnet so as to form a second magnetic gap to the side of the one principal surface of the diaphragm, and (iii) polarized in a direction perpendicular to the vibration direction of the diaphragm; a first plate made from a ferromagnetic material and which is sandwiched between the first magnet and the second magnet without an air gap; and a first coil which is (i) wound to form an elongated ring shape, and (ii) situated on the diaphragm such that long sides of the first coil are in parallel with the long sides of the diaphragm and such that each of the long sides of the first coil is situated within a range of each of the first magnetic gap and the second magnetic gap, wherein a height of the first plate, a height of the first magnet, and a height of the second magnet are identical in the vibration direction of the diaphragm, wherein surfaces, which face the diaphragm, of the first magnet, the second magnet, and the first plate are located on a common plane, wherein the electro-acoustical transducer further comprises: a second plate situated so as to be in contact with a pole face of the first magnet, the pole face being opposite to another pole face of the first magnet which is in contact with the first plate; and a third plate situated so as to be in contact with a pole face of the second magnet, the pole face being opposite to another pole face of the second magnet which is in contact with the first plate, wherein respective surfaces, which face the diaphragm, of the second plate and the third plate are located on a plane closer to the diaphragm than respective surfaces, which face the diaphragm, of the first magnet, the second magnet, and the first plate, wherein a cross section of the edge is convex toward another principal surface of the diaphragm, and wherein the second plate and the third plate are respectively situated such that the respective surfaces, which face the diaphragm, of the second plate and the third plate, face the edge.