Magnet-Only Loudspeaker Magnetic Circuits: A Solution for Significantly Lower Current Distortion

摘要

This paper presents a case study that leads to a significant decrease of current distortion caused by the magnetic circuit of the loudspeaker. The solution consists in removing all of the nonlinear soft-iron pieces that are used in traditional loudspeaker motors. Thus, in the loudspeaker motors we study, the static magnetic field is only created thanks to a combination of permanent magnets. This combination leads to the realization of the so-called magnet-only loudspeakers. Two loudspeakers are compared in the study: the first sample is a mass-produced 6.5-inch loudspeaker. The second sample is built replacing the magnetic circuit of the first loudspeaker by the magnet-only structure. Thus, the moving part, including the voice-coil, the diaphragm, and the suspensions is kept identical for both samples, leading to a comparison of both loudspeakers only based on their motor. The loudspeaker with the magnet-only motor shows significantly lower current distortion than the original loudspeaker. A possible explanation of such a decrease of distortion is given based on results of a set of measurements with blocked voice-coil.