Energy conversion principle: moving coil type, isomagnetic type, electrostatic type, electret, moving iron type. Transducer is mainly divided into two categories: Dynamic and Electrostatic earphones. Although there are several other types such as magnetic type in addition to these two types, they have either been eliminated or used for professional use. The use market share is very small.
The principle of dynamic earphones: most (about 99%) earphone earplugs are of this type. The principle is similar to that of ordinary speakers. The coil in a permanent magnetic field is connected to the diaphragm, and the coil drives the diaphragm to sound under the signal current. Electrostatic earphones: The diaphragm is in a changing electric field. The diaphragm is extremely thin and accurate to a few microns (currently STAX's new generation of electrostatic earphone diaphragms are accurate to 1.35 microns). The coil drives the diaphragm to sound under the drive of the electric field.
Moving coil earphones are the most common and common earphones. Its driving unit is basically a small moving coil speaker, which is driven by a voice coil in a permanent magnetic field to vibrate the diaphragm connected to it. The coil in the permanent magnetic field is connected to the diaphragm. The coil drives the diaphragm to produce sound under the signal current drive. Moving coil earphones are more efficient, and most of them can be driven by the earphone output on the audio, and they are reliable and durable.
The driver of the isomagnetic earphone is similar to the reduced flat speaker, which embeds the flat voice coil in the thin diaphragm, like a printed circuit board, which can evenly distribute the driving force. The magnets are concentrated on one or both sides of the diaphragm (push-pull), and the diaphragm vibrates in the magnetic field formed by it. The diaphragm of a magnet earphone is not as light as the diaphragm of an electrostatic earphone, but it has the same large vibration area and similar sound quality. It is not as efficient as a moving coil earphone and is not easy to drive.
Electrostatic earphones have a light and thin diaphragm, which is polarized by a high DC voltage. The electrical energy required for the polarization is converted by alternating current, and it is also battery-powered. The diaphragm is suspended in the electrostatic field formed by two fixed metal plates (stator). When the audio signal is loaded on the stator, the electrostatic field changes and drives the diaphragm to vibrate. The single stator can also drive the diaphragm, but the push-pull form of the double stator has less distortion. Electrostatic earphones must use special amplifiers to convert audio signals into voltage signals of hundreds of volts. The electrostatic earphones can also be driven by connecting a transformer to the output of the power amplifier. Electrostatic earphones are expensive and difficult to drive, and the sound pressure level that can be reached is not as large as that of moving coil earphones, but it has a fast response speed, can reproduce all kinds of tiny details, and has very low distortion.
Electret earphones are also called fixed electrostatic earphones. The diaphragm itself is polarized or the electrostatic field emitted by polarized materials outside the diaphragm is polarized, and no special equipment is required to provide a polarization voltage. Electret earphones have most of the characteristics of electrostatic earphones, but the electret will gradually depolarize and need to be replaced, and its life span is about 5-10 years.
Inside the moving iron earplugs, the voice coil is wound on a precision iron piece called a "balanced armature" located in the center of the permanent magnetic field. This piece of iron drives the diaphragm to make sound under the action of magnetic force. The moving coil directly drives the diaphragm, while the moving iron is conducted to the center point of a miniature diaphragm through a precisely structured connecting rod, thereby generating vibration and sound. In terms of unit location, the traditional moving coil earplugs cannot put the entire sound unit in the ear, while the moving iron type can be easily put into the ear canal because the unit is much smaller. This approach effectively reduces the area of the ear part and can be inserted into the deeper part of the ear canal. Since the geometric structure of the ear canal is much simpler than that of the auricle, it is a round shape, so a soft silicone sleeve has a good sound insulation and anti-leakage effect compared to traditional earplugs.
1 The earphones have coils on the left and right magnetic cores, and two small iron pieces. The iron pieces will vibrate with the strength of the magnetism, thus producing sound. Since the coil is connected to the audio output interface, the strength of the current in the earphone determines the strength of the magnetism and the size of the sound.
2 Since a wire is broken, no current flows through the coil, and no sound can be heard.
3 The radio is generally superheterodyne. The antenna coil is used to receive radio waves. Because the radio waves are very weak, an antenna of several tens of centimeters is needed to connect to it. The longer the antenna, the better the effect. The wire inserted into the headset acts as an antenna.
4 The sensitivity of the earphone is very high, and only a small current can be passed through the coil to make sound. The audio output current of the pocket radio is relatively weak, and the earphone is just right.