A loudspeaker , comprising: a frame ; a yoke fixed to the frame ; a magnet fixed to the yoke ; a plate fixed to a first surface of the magnet , the first surface being opposite to a second surface of the magnet which is fixed to the yoke ; a voice coil arranged, in a vibratable manner, in a first magnetic gap (G1) formed between the yoke and the plate ; a diaphragm having a dome shape and an outer edge portion joined to the voice coil ; a support member which supports the diaphragm in a vibratable manner, and is composed of a plurality of edges (108a-108d), one end of each edge (108a-108d) being fixed to the frame , and a magnetic fluid disposed between the plate and the voice coil , wherein the plate is composed of a flat-plate part which is fixed to the first surface of the magnet , and has, at a surface opposite the magnet , a planar portion (P) extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion (P), and protrudes toward the diaphragm , and a through-hole is formed so as to penetrate through the yoke , the magnet , and the plate , the through-hole connecting a space outside the loudspeaker with a space on a back surface of the diaphragm , the protruding part extending into the through-hole so as to fix the yoke , the magnet , and the plate , an end of the protruding part on the flat-plate part side being in a dome shape substantially the same as to that of the diaphragm , thereby reducing the volume of the space between the diaphragm and the plate , and an air flow path is provided so as to penetrate through the protruding part along the flat-plate part . a frame ; a yoke fixed to the frame ; a magnet fixed to the yoke ; a plate fixed to a first surface of the magnet , the first surface being opposite to a second surface of the magnet which is fixed to the yoke ; a voice coil arranged, in a vibratable manner, in a first magnetic gap (G1) formed between the yoke and the plate ; a diaphragm having a dome shape and an outer edge portion joined to the voice coil ; a support member which supports the diaphragm in a vibratable manner, and is composed of a plurality of edges (108a-108d), one end of each edge (108a-108d) being fixed to the frame , and a magnetic fluid disposed between the plate and the voice coil , wherein the plate is composed of a flat-plate part which is fixed to the first surface of the magnet , and has, at a surface opposite the magnet , a planar portion (P) extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion (P), and protrudes toward the diaphragm , and a flat-plate part which is fixed to the first surface of the magnet , and has, at a surface opposite the magnet , a planar portion (P) extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion (P), and protrudes toward the diaphragm , and a through-hole is formed so as to penetrate through the yoke , the magnet , and the plate , the through-hole connecting a space outside the loudspeaker with a space on a back surface of the diaphragm , the protruding part extending into the through-hole so as to fix the yoke , the magnet , and the plate , an end of the protruding part on the flat-plate part side being in a dome shape substantially the same as to that of the diaphragm , thereby reducing the volume of the space between the diaphragm and the plate , and an air flow path is provided so as to penetrate through the protruding part along the flat-plate part . <EOS>