Currently, most telephone headsets have the working principle of moving coil type electro-acoustic conversion. As the earliest electro-acoustic conversion method used on headsets, the moving coil type is similar to the conventional speaker system. The diaphragm is structurally connected to a cylindrical coil in a permanent magnetic field, and the coil drives the diaphragm to sound under the signal current. The working efficiency of the moving coil headset is higher than others. Theoretically, the larger the size of the drive unit, the better the performance.
There are differences in the diaphragm structure between a moving coil corded phone headset and a common soundbox. The edges of the diaphragm of the soundbox are generally fixed on the elastic medium, which is mostly conical in shape. And the vibration power is provided by elastic media.
For moving coil corded phone headset, the diaphragm edges are directly fixed on the frame of the drive unit. The source of vibration is completely provided by the expansion and contraction of the diaphragm. Therefore, the material selection and shape design of the diaphragm of the moving coil corded phone headset drive unit has a direct relationship with the sound performance.
Due to the high manufacturing technology and high cost, the price of electrostatic telephone headsets is often more than ten thousand yuan. The working principle of electrostatic telephone headsets is different from moving coil telephone headsets. The diaphragm is polarized by a high DC voltage and is in an electrostatic field formed by two fixed metal plates. And the diaphragm is driven by the electric field force to produce sound.
The electrostatic telephone headset needs to convert audio signals into voltage signals of hundreds of volts, so they must be driven by using special amplifiers.
The structure of the electrostatic telephone headset has inherent advantages over the moving coil telephone headset. The most important thing is that the diaphragm is very light and thin, which is only about 1/10 of the diaphragm of a moving coil headset. This lighter and thinner diaphragm can bring faster, better transient response and more detailed sound.
In addition, the diaphragm of the moving coil telephone headset has structural limitations. There is always the problem of segmented vibration, which affects the uniformity of the three-frequency. However, the diaphragm of the electrostatic telephone headset is fixed between the parallel fixed plates. The electric field it receives is completely uniform and can be driven linearly.
The flat-diaphragm telephone headset can also be called the isomagnetic headset. The working principle is different from the moving coil headset and the electrostatic headset, and it is very similar to flat diaphragm speakers. It embeds a flat voice coil in a thin diaphragm, where the magnets are concentrated on one or both sides of the diaphragm. And the diaphragm will vibrate in the magnetic field formed by it.
Both flat-diaphragm telephone headset and electrostatic headset can achieve linear diaphragm movement without having problems with segmentation vibration. The flat-diaphragm headset can also withstand more input power and lower distortion under loud sound pressure. However, it has low work efficiency and sensitivity, and it often requires high-power and high-current output amplifiers to cooperate. In addition, it is not suitable for long-term wear due to its large size and weight.