Speaker with a molded plastic frame including a positioning projection, and a method for manufacturing the same

A method for manufacturing a speaker, comprising the steps of:

• using a plastic frame having integrally formed, a closed bottom cylindrical magnetic circuit holding portion, a first mounting portion for fixing an outer circumferential edge of a diaphragm above said closed bottom cylindrical magnetic circuit holding portion, a plurality of engaging projections extending from an inner surface of said closed bottom cylindrical magnetic circuit holding portion, a second mounting surface for enabling mounting of the frame, and a positioning projection in a central portion on a bottom surface;
• concentrically putting a bottom plate, which has a magnet guide in an upper surface, a positioning recess in a central portion at a bottom surface, and a center pole, by engaging said positioning recess with said positioning projection of said closed bottom cylindrical magnetic circuit holding portion;
• putting a ring-shaped magnet on said bottom plate by utilizing said magnet guide of said bottom plate;
• putting on said magnet a top plate having a plurality of engaging portions horizontally extending along the outer circumferential portion thereof by using said center pole as a guide such that said engaging portions of the top plate are offset in a rotational direction relative to said engaging projections;
• and
• rotating said top plate in a predetermined direction with respect to the frame such that said engaging portions of the top plate engage with and move along slanted surfaces defined by lower surfaces of said engaging projections of the frame until said top plate is urged to a substantially maximum downward position and tightly holds said ring-shaped magnet in the closed bottom cylindrical magnetic circuit holding portion wherein a magnetic circuit formed of said bottom plate, said ring-shaped magnet, and said top plate is firmly fixed in said frame.