Nowadays permanent magnets are widely used in many fields. In addition to the new energy (e.g. motors, wind turbines), magnets are also used in electro-acoustic (such as speakers, receivers, microphones, alarm, stage audio, car audio, etc.). In the early stage of loudspeaker development, all moving-coil loudspeakers are driven by solenoid because of no suitable permanent magnet. After the Second World War, strong rare earth alloy magnets are successful developed. Then moving-coil loudspeaker begins to use permanent magnet. This greatly improves the stability and authenticity of sound and let the moving-coil become the main system of modern loudspeaker.


The magnets in the loudspeaker create magnetic field and help to convert electricity into sound waves. There are three types of magnets used in loudspeakers: ferrite, AlNiCo and NdFeB. The most common one is ferrite magnet, lower in cost but heavy and low magnetic force. Neodymium magnet is the most powerful permanent magnet and weighs a lot less than ferrite magnet and can be used in small product. Therefore it is the critical material of High-end electro-acoustic products where lower reducing weight is always a goal.



When you need loudspeaker to work on special environment, there are several temperatures series for neodymium magnet which you can choose, e.g. N (80℃), M (100℃), H (120℃), SH (150℃), UH (180℃), EH (200℃); under each temperature, there are different grades based on magnetic force, e.g. N38, N40, N45 etc. AlNiCo is in the middle about magnetic force among three type material magnets. It can work on 300℃ high temperature and tend to last longer, but much expensive.


When refer to 100mm loudspeaker, we mean the diameter of ring magnet in the speaker is 100mm. According to the different magnet specification, it is not right that the bigger magnet, the better loudspeaker. Although the material and size of magnet in loudspeaker are the same, you may get products with different sound quality. About this, you need to know magnetization level. Try to keep every magnet has been full charged. Sintered ndfeb magnet is always plated to avoid oxidation. The thickness of coating will affect magnetization. So loudspeaker magnet usually uses Zn coated or thin Ni coated.

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