Foster Electric Company, Limited

Hidetoshi Shirakawa

Takeshi Yoshimura

Rintaro Kohara

An elongated oval track-shaped loudspeaker has a diaphragm of a track-shape having major and minor axes, and a pole piece of an elongated oval shape and disposed to conform its major axis to that of the diaphragm, whereby a sufficient space is secured for a width size of a diaphragm-supporting damper at its portions on both sides along the major axis of the diaphragm, a magnet around the pole piece is enlarged, and the pole piece is dimensioned in its sectional area to correspond to the magnet to cause no magnetic saturation.

Track-shaped loudspeaker

A loudspeaker unit includes a magnetic system of dual magnetic gaps formed with a permanent magnet disk carrying on both sides top and bottom plates and a cylindrical yoke surrounding the plates to form therebetween upper and lower magnetic gaps, and a vibratory system formed with a cylindrical voice coil bobbin carrying upper and lower voice coils for use in the dual magnetic gaps as disposed in half off-set state with respect to the gaps and a diaphragm coupled to upper end of the bobbin, the bobbin being supported by upper and lower dampers with respect to the magnetic system for vibration in axial directions of the magnetic system, allowing the bobbin to be supported at fulcrums positioned above and below voice-coil driving points.

Loudspeaker unit and loudspeaker system employing the unit

A loudspeaker has two magnets disposed directly with respect to voice coils for generating a repulsion magnetic field at the voice coils, without interposition of yoke but with mutually repulsing magnetic polarities of the magnets, and a diaphragm directly coupled at inner peripheral edge substantially to the center of outer periphery of the voice coils. Driving force is transmitted highly efficiently from the voice coils to the diaphragm, and the loudspeaker can be sufficiently minimized in the thickness and weight.

Growing community of inventors

Akishima, Japan

Hidetoshi Shirakawa