Patent ID: 8542861

Claim:
A loudspeaker comprising: a diaphragm; a magnetic circuit that is provided on a rear side of the diaphragm, the magnetic circuit comprising a yoke shaped as a container opening towards the diaphragm and including a bottom wall having an inner surface that faces the diaphragm, a plate that cooperates with the yoke to form a magnetic gap therebetween, and a magnet having a first surface fixed to the plate and a second surface, opposite to the first surface, fixed to the inner surface of the bottom wall of the yoke; a voice coil that is directly or indirectly joined to the diaphragm along an outer shape of the diaphragm and extends into the magnetic gap to create a first passage within the magnetic gap that communicates between a space between the rear side of the diaphragm and an upper surface of the plate and a space outside of the loudspeaker; a magnetic fluid that is disposed within the magnetic gap; and a plurality of first edge pieces that are provided at different positions at an outer portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a curved cross-sectional shape when viewed in a longitudinal cross-section taken along a central axis of the loudspeaker, wherein an entirety of the outer edge of the diaphragm is not supported and the plurality of first edge pieces only support a portion of the diaphragm at the outer portion, wherein the magnetic fluid (i) is located between the plate and the voice coil in the magnetic gap, (ii) contacts the voice coil along an entire inner circumference of the voice coil, extends across the first passage that communicates between the space between the rear side of the diaphragm and the upper surface of the plate and the space outside of the loudspeaker, and contacts the plate along an entire outer circumference of the plate to seal the first passage, and (iii) is exposed to the space between the rear side of the diaphragm and the upper surface of the plate and the space outside of the loudspeaker via the first passage, and wherein the bottom wall of the yoke, the magnet and the plate have a first hole that passes therethrough and forms a second passage that communicates between the space between the rear side of the diaphragm and the upper surface of the plate and the space outside of the loudspeaker.