The main magnets used in audio are neodymium-iron-boron and ferrite. They exist in various sizes in the shape of rings or disks. NdFeB, on the other hand, is commonly used in medium and high-grade products. It produces audio with excellent sound quality, good sound elasticity, good sound performance and accurate sound field positioning. With excellent performance, small and light NdFeB began to gradually replace large and heavy ferrite. Neodymium-iron-boron magnets also play an important role in car stereos, with car stereos as the carrier, they can provide vehicle passengers with in-car entertainment and information. All car stereos have voice coils, which are coils placed in the middle area of the magnet, where the magnet is wrapped around a pole post. As current passes through the car amplifier, it causes the cone to be forced upward and downward, producing audible sound.