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Headphone driver unit analysis
Release:2018-07-04 15:55:32 browse:
Today there is many headsets on the market, mostly because the enjoying of music is a natural necessity of human beings. In technical terms the headset is a pair of conversion units, where the signal is received from a media player or an amplifier and transfer the signal to the ear speaker, so we can hear the acoustic sound. Headphones are generally separated from the media player and are connected by cables or wirelessly. The advantage is that you can listen to the sound for yourself without affecting other people, because it can isolate from the environmental noise. A headset is very helpful for people who work in noisy environments, for instance in a music studio or when working as a DJ.
 
According to the development of different technologies, the drive unit of headphones can be divided into various categories, and we generally recognize the unit classification which is distinguished by the principle of energy conversion (Transducer). According to the acoustic drive mode of transducer used in earphone, it can be divided into different drivers as moving coil (Dynamic) and electrostatic (Electrostatic), balanced armature, biologic membrane, piezoelectric, electromagnetic and so on.
 
Principle diagram of moving coil earphone:
Moving coil is designed by a coil that is connected directly to a membrane, where the coil is located inside a magnetic field and moves when current is applied to it. Today most of the headsets are built very similar to the conventional loudspeaker with the permanent magnetic field in the winding of the cylindrical coil that is connected with the diaphragm, where the coil driven diaphragm creates a sound signal in the current drive. The headset dynamic loudspeaker diaphragm is different from the speaker diaphragm edge fixed in the elastic medium (folding ring and damper) on (for example in large calibre bass units), because the diaphragm is generally flat conical and made of elastic medium, which provides vibration system in force.
Today, moving coil drive unit technology is very mature and the technology is not expected to change very much in the near future. The current improvement is mainly to develop higher density permanent magnet, more ideal vibration diaphragm material and design. At the same time, the maturity of technology makes its corresponding cost lower, more competitive, and results in a high competition in the market.
 
Balanced armature type:
The principle of energy exchange is similar to the moving coil unit. The armature (a metal strip) is placed between two magnets and a coil is placed around the armature. The armature tip is positioned exactly in the centre between two magnets (balanced armature). Current through the coil will inject flux into the armature, setting it in motion. A drive pin connected to the armature on one end moves the membrane on the other end producing sound. It is common in high-end headphones, usually using the earplug as the type of headphones, because the driver is very small.
 
 
 
Electrostatic: also known as the electrostatic plane vibration membrane
The speakers use a thin flat diaphragm usually consisting of a plastic sheet coated with a conductive material such as graphite sandwiched between two electrically conductive grids, with a small air gap between the diaphragm and grids. The static type is also called static plane diaphragm, the conductive body (stator plates) direct plating or printing on plastic film, which is very thin, and accurate to a few microns (the electrostatic headset diaphragm of a new generation of STAX is accurate to 1.35 micron). The strong static electric field, usually a DC high voltage generator generates a signal through the stator plates creating an electric field, driving the diaphragm and giving vibration sound. The advantages are linearity, little distortion (electric field is more uniform than magnetic field), high frequency and transient response (light quality of vibration film). The disadvantage is the need for specialized drive circuits and electrostatic generators, low frequency response, and the construction is very expensive, and the efficiency is not high either.
 
Biological vibration membrane headphones in a moving coil construction
A bacterium, called acetobacter, produces very fine cellulose (cellulose) after eating sugar. The most advanced biological technology takes about 2 days to grow this fibre to the thickness of 2mm. Afterwards, it is dehydrated, and the metal abrasive tools are made to compress them to 20 µm thickness. Thus, the biological vibration film was born. The vibration film has a sonic speed (stiffness / density squared root) that matches the aluminium film, the titanium film and is also paper, which can reproduce the very natural sound.