Magnetic loudspeaker (Tongue spring speaker)
The magnetic loudspeaker is also known as the tongue Spring speaker. In the magnetic loudspeaker structure, there is an electromagnet of movable core between the poles of the permanent magnet. When there is no current in the coil of electromagnet, the movable core is attracted by the attraction of the two poles of the permanent magnet, and it remains stationary in the central part. When there is an electric current flowing through the coil, the movable core is magnetized and becomes a bar magnet.
With the change of the current direction, the polarity of the strip magnet also changes correspondingly, so that the movable core rotates around the fulcrum, and the vibration of the movable core is transmitted by the cantilever to the vibrating film (paper basin) to promote the air thermal vibration.
II. ION Speaker
In a general state, the molecular weight of the air is neutral and not electrically charged. But after high-voltage discharge become charged particles, this phenomenon is called dissociation. Using the free air to vibrate the audio voltage, the sound wave is generated, which is the principle of the ionic loudspeaker.
In order to ionization, it is necessary to add 20MHz of high-frequency voltage, and in its overlapping audio signal piezoelectric. The ion loudspeaker is composed of the high-frequency oscillation part, the audio signal modulation part, the discharge cavity and the number cylinder. The discharge cavity uses the quartz rod of 8mm diameter to open the hole in the center, opens the quartz tube, inserts an electrode into it, the other electrode assumes the cylindrical sleeve outside the quartz tube, because uses the silent discharge form, only the center needle electrode has the loss, may change the central electrode regularly.
The ionic speaker differs from other speakers in that there is no vibrating film, so the transient and high-frequency characteristics are good, but the structure is very complex.
III. Ultrasonic SPEAKER
The so-called ultrasonic speaker, refers to the previous few years has just developed successfully, is entering the practical phase of the ultrasonic sound technology.
The principle of the ultrasonic technology: it does not use any of the traditional form of the loudspeaker unit, but the use of ultrasonic generators to produce two beams through a special treatment of the ultrasonic beam, when the two beams at the same time acting on the ear of the tympanic membrane can be caused by the interaction of the hearing.
We know that there is no sound when a beam is acting on the tympanic membrane. Because the ultrasonic speed has a strong and controllable directivity, the intersection of two beams can point to a very small range of the sound region, when the ear is in the area, you can hear the sound, and the human ear once left the area will not hear.
Using this feature, now some of the top luxury cars are starting to equip themselves with a number of such sonic systems, forming a listening area on each seat, which allows each passenger to choose what they like, without interfering with each other and without affecting the conversation between passengers.
IV. Electrostatic speaker (capacitive speaker)
Electrostatic loudspeaker is used to add to the capacitor plate on the static power and work of the loudspeaker, its structure, as a result of positive and negative to the capacitor-like, so also known as capacitive speaker.
The electrostatic loudspeaker has two pieces of thick and hard material as the fixed plate, the plate has this can through the sound, the middle plate is using thin and light material as the vibrating film (such as aluminum film). The vibrating film is fixed, tightened and maintained at a considerable distance from the fixed pole, even on the large vibrating film, and it will not collide with the fixed pole.
The current voltage (called bias) between the two electrodes of the electrostatic loudspeaker. If the output of the audio voltage between the two electrodes, and the original output voltage overlap, the formation of alternating pulse voltage, this pulsating voltage generated in the gap between the attraction of the strong and weak, and the vibration of the film is thus audible.
The advantages of electrostatic loudspeaker is the entire vibrating film with the same phase vibration, vibration film light, small distortion, you can replay extremely crisp sound, there is a good analytical force, detail clear, sound lifelike. Its disadvantage is the low efficiency, the need for High-voltage DC power supply, easy to absorb dust, vibration film increased distortion will increase, not suitable for listening to rock, heavy metal music, the price is relatively expensive.
V. Airflow modulation speaker (airflow loudspeaker)
The airflow modulated loudspeaker is a loudspeaker which uses compressed air as energy source and uses audio current to modulate airflow. It consists of a gas chamber, a modulating valve, a cylinder and a magnetic circuit. Compressed air flow from the air chamber through the valve, by the addition of audio signal modulation, so that the fluctuation of the airflow in accordance with the external audio signal changes, and the modulation of the air flow through the cylinder coupling, to improve the efficiency of the system.
Generally used for high-intensity noise environment test sound source or long-distance broadcast.
VI. Piezoelectric speaker
The use of piezoelectric materials in the inverse piezoelectric effect of the speaker is called piezoelectric loudspeaker. Dielectric (such as quartz, potassium sodium tartrate and other crystals) under the pressure of polarization, so that the surface potential difference between the two sides, we call it "piezoelectric effect." Its inverse effect, that is, placed in the electric field of the dielectric will occur elastic deformation, known as "inverse piezoelectric effects" or "electrical contraction."
Compared with the electric loudspeaker, the piezoelectric loudspeaker does not need the magnetic circuit, and the static speaker does not need the bias, the structure is simple, the price is cheap, the disadvantage is the distortion is big and the work is unstable.