Now the small earplugs can be divided into moving coil and moving iron.
Dynamic voice unit is a round polyester diaphragm, coated with metal powder, followed by connecting the solenoid coil. After power by the magnetic force vibration sound. Dynamic earplugs are characterized by the sound of emotions, sense of natural ease, but the sound detail and level of poor, slow speed. Common models such as Sennheiser MX90, CX300, AKG K701.
The moving iron type principle is similar to the moving coil, which is a small piece of metal. As for the S type magnet, the connecting rod is forced to vibrate. Moving iron sound characteristics of the sound speed, rich in detail, but the lack of emotion, the sound field is not natural enough, not suitable for listening to music, because the moving iron was originally used for hearing aids, but moving iron unit due to the principle of sound constraints, only Can be made into a closed ear. Common models are WESTONE UM1, ETYMOTIC ER4, UE10 and so on.
Most common earbuds and headphones nowadays are moving coils.