1. The magnetic speaker has an electromagnet with a movable iron core between the two poles of the permanent magnet. When there is no current in the coil of the electromagnet, the movable iron core is attracted by the phase-level attraction of the two magnetic poles of the permanent magnet and remains stationary in the center; When a current flows through the coil, the movable iron core is magnetized and becomes a bar magnet. With the change of the current direction, the polarity of the bar magnet also changes correspondingly, so that the movable iron core rotates around the fulcrum, and the vibration of the movable iron core is transmitted from the cantilever to the diaphragm (paper cone) to push the air to thermally vibrate.

2. Electrostatic speaker It is a speaker that uses the electrostatic force added to the capacitor plate. In terms of its structure, it is also called a capacitor speaker because the positive and negative electrodes are opposite to each other. Two thick and hard materials are used as fixed plates, which can transmit sound through the plates, and the middle plate is made of thin and light materials as diaphragms (such as aluminum diaphragms). Fix and tighten around the diaphragm and keep a considerable distance from the fixed pole. Even on a large diaphragm, it will not collide with the fixed pole.
3. Piezoelectric speakers A speaker that uses the inverse piezoelectric effect of piezoelectric materials is called a piezoelectric speaker. The phenomenon that the dielectric (such as quartz, potassium sodium tartrate and other crystals) is polarized under the action of pressure, causing a potential difference between the two ends of the surface, which is called the “piezoelectric effect”. Its inverse effect, that is, the elastic deformation of the dielectric placed in the electric field, is called the “inverse piezoelectric effect” or “electrostriction”.