Generally speaking, earphones are divided into 5 categories: piezoelectric headphones, moving iron earphones, moving coil earphones, electrostatic headphones, and pneumatic headphones.
Piezoelectric headphones: use the piezoelectric effect of piezoelectric ceramics to produce sound. High power and high frequency. Defects: large distortion, high driving voltage, low frequency echo error, anti impact differential. These earphones are mostly used for telegraph receiving and sending. A small number of headphones use piezoelectric ceramics as high pitched sound units.
Moving iron earphones: using the electromagnet to attack the alternating magnetic field, the oscillation is some of the iron sheet suspended in front of the electromagnet, the signal will change the magnetic field of the electromagnet when the electromagnet is passing through the electromagnet, and then the vibration of the iron sheet is sound. The advantage is long service life and high power. The defects are large distortion and narrow frequency response. A telephone receiver used in the early stage.
Moving coil earphone: This is the most popular earphone mode nowadays. The coil is fixed to the vibration film and is placed in a fixed magnetic field which is attacked by a permanent magnet. The signal is cut through the magnetic line through the coil and then oscillates together by the vibrating membrane. The advantage is relatively simple manufacturing, good linearity, small distortion and wide frequency response. The defect is low power.
Electrostatic headset: also called an electrostatic plane vibrating film, which is directly electroplated or printed on a thin plastic film by an aluminum (or other conductive metal) coil and placed in a strong static electric field (usually made up of a DC high pressure attack device and a fixed metal sheet). . The advantages are good linearity, small distortion (uniform electric field than magnetic field), good transient response (light diaphragm quality) and high frequency echo. The defect is low frequency echo, poor demand driving circuit and electrostatic stall device, and the price is high. The power is not high.
Pneumatic headphones: air pumps and air valves are used to control the airflow, and directly control the air pressure and flow, causing the air to oscillate. Sometimes the air valve is replaced by a high power loudspeaker. Such earphones are commonly used on aircraft, and this earphone is actually only an airway. The advantages are electric drive, unlimited parallel connection and high power. The defects are large distortion, narrow frequency response and noise.
Moving coil headset: is the most widely used headset, according to the different use of the intention, divided into many types, different manufacturers have different features of the headset skills, each of the characteristics.