Moving coil loudspeaker using thin magnet

Claim 1

A motor for a loudspeaker which comprises a. a base plate formed of an integral flat member having a dished portion in the center thereof upset by embossing to produce a flat annular flange in one plane and the dished portion comprising a flat part in a parallel plane spaced therefrom and connected by an annular imperforate web, said dished portion having an aperture in the center thereof, b. a cylindrical post, the lower end thereof being fastened to the base plate in said aperture and having an end circumferential surface of predetermined outside diameter, c. an annular magnet having an aperture in the center thereof mounted on the flat annular flange of the base plate coaxially with the post, d. an annular front plate having a central aperture and being attached to the magnet such that the Central aperture is coaxial with said post, said central aperture having a predetermined inside diameter larger than the said outside diameter of the cylindrical post such as to form an air gap therewith, e. the magnet being sandwiched between the base plate and the front plate with its aperture adjacent to the end circumferential surface of the post, the said air gap being adapted to receive therein a single voice coil of helical configuration having an inner diameter slightly larger than the outside diameter of the post and an outside diameter slightly smaller than the diameters of the apertures of the magnet and the front plate so as to be capable of sliding along the post, f. and wherein said embossed dished portion of the base plate is adapted to afford additional space for voice coil travel.