Patent ID: 6639993
Filing Date: 2003-10-28
Classification: H04R

Abstract:
A loudspeaker comprising:a speaker frame; a diaphragm connected to said speaker frame in a manner capable of vibration; a voice coil which is formed on a voice coil bobbin and is connected to said diaphragm for vibrating the diaphragm; a permanent magnet having a central opening; an upper plate having a central opening and provided on the permanent magnet; and a pole piece disposed coaxially within the central opening of said permanent magnet to form an air gap between said pole piece and said upper plate into which said voice coil is disposed, the pole piece having an axial through hole at its center for establishing an air passage between inside and outside of the loudspeaker; wherein a top area of the through hole of the pole piece is curved with an S-shape in cross section and an inner diameter of the through hole is increased toward the inner top thereof, and wherein an outside surface of an upper end of said axial through hole is curved to promote smooth air flows between an inner area of said voice coil bobbin and the outside of said loudspeaker.