Patent ID: 8422728

Claim:
An electromagnetic converter comprising: a magnetic circuit having a permanent magnet, a frame fixing one magnetic pole face of said permanent magnet thereto and having an opening on a side of another magnetic pole face of said permanent magnet, and a plate fixed to said other magnetic pole face; a diaphragm having a top portion positioned to cover said plate and four side portions formed in such a way as to extend from said top portion toward said permanent magnet, and positioned between said plate and said opening of said frame, and having a voice coil pattern formed on one surface or both surfaces thereof; a first holding portion joined to a periphery of the top portion of said diaphragm, and a periphery of said opening of said frame, for holding said diaphragm in such a way that said diaphragm can move; and a second holding portion joined to edges of side portions of said diaphragm, and an inner surface of said frame, for holding said diaphragm in such a way that said diaphragm can move wherein the top portion and the four side portions of the diaphragm are made of the same material, wherein said diaphragm is made from a thermoplastic resin sheet, and the four side portions of said diaphragm are formed by hot press forming both sides in a direction of a length of the sheet and both sides in a direction of a width of the sheet, and the voice coil pattern is arranged on both the side portions in said direction of the length of the sheet and on the top portion.