Sintered neodymium magnet are widely used in speaker, it provides a permanent magnetic
field for the speaker coil, which is embedded in the paper of the speaker cone. When the
audio signal flows throw the speaker coil, it generates a small magnetic field. This small
magnetic field is repelled to the permanent magnetic field. Thus the paper cone moves
away from or closer towards the back of the speaker. Hence as the strength of the audio
signal wiggles the paper cone wiggles back and forth, and you get sound waves that
match the audio signal.
Ordinary ferrite magnet is mainly used for low-end headphones. Neodymium magnets
for high-end headphones, so it has better sound quality, good elasticity, good voice
performance, and accurate positioning of sound field.