耳机知识（Headphone knowledge）

耳机知识（Headphone knowledge） 耳机知识(Headphone knowledge) .txt the important thing in life is not where you stand, but where you're going. Don't use your own needs to measure others' giving, or always complain. A headset is mainly composed of four parts: head, about sounding unit, earmuffs and lead. The headband is the function of fixed around the sound unit, will be placed in the head on both sides of the connection, and its structure and its unit determines the pressure on the head and ear headband, affecting the headset wearing comfort. Earmuffs are head and sound unit contact parts, it is very important for the moving coil of the headset, its function is to ensure the low frequency reflected low frequency playback. Earmuffs are generally two kinds of style, a kind of pressure in the ears, ear ear pressure (Supra-aural), another ear of a goblet, around the ears, called around the ear ear muffs (Circumnaural). Ear to soft and comfortable, its interior is generally filled with sponge, outside covered with leather or cloth. Earmuffs materials used are absorption of medium and high frequency, it makes the ears and diaphragm forming a distance, and a cavity is formed in the headset and the head. Large internal space around the ear ear muffs, voice can act on the auricle, forming good sense of space. A good design of the headset has fully considered the role of high-grade earmuffs, so the headset can not be damaged or earmuffs replaced. The headset is connected to the line wire headset output end of the amplifier circuit and the headset voice coil, copper quality headset line uses the extension core (OFC) line, through strict insulation and shielding treatment, eliminate interference of copper impurity in the impact on signal transmission and external clutter. The end of the headphone cord is a plug, there are two specifications: 6.35mm and 3.5mm, that is, the usual size plug, 6.35mm plug for professional audio and civil audio equipment, 3.5mm plug for portable devices. General high fidelity headphones will provide plug converters to ensure the use of headphones on various devices. The plugs of middle and high grade earphones are gold-plated, which is not for beauty, mainly to prevent the plug from oxidizing and affecting the sound. It can also provide the largest contact area due to the golden slip and softness. Low grade headphones often use nickel plated plugs, although this can also prevent oxidation, but has a negative impact on sound. The sound unit of earphone is the most complicated and the most technical part of earphone design. The working principle and the dynamic moving coil headset speaker, audio signal input after the voice coil, the electromagnetic field generated by the voice coil with signal change change, electromagnetic field and magnetic circuit changes the interaction to promote the voice coil and diaphragm, the diaphragm pushes air sounding. The sound cell of moving coil earphone consists of three parts: magnetic circuit system, vibration system, cavity and hole. The magnetic circuit system is composed of permanent magnet and pole plate, which has a direct impact on the performance and reliability of the headset, the permanent magnet side plate type, the other side is a "pole T", a small size annular magnetic gap formed between the plate and the pole, the voice coil vibration system the hanging in the gap. Permanent magnet is usually used for high fidelity headset neodymium magnets with excellent performance, the earlier use headset type SmCo magnets expensive, low-grade ferrite generally use the headset. The design of magnetic circuit system is complicated, and the magnetic circuit of high grade headphones such as SENNHEISER HD580 and HD600 is designed by computer aided design. The production process of magnetic circuit is also an aspect affecting its performance. The design and manufacture of an excellent magnetic circuit system can effectively control the vibration system, Higher sensitivity, smaller distortion, better transient and lower frequency are obtained. The vibration system consists of a voice coil and a diaphragm. The diaphragm is an acoustic radiation element, which promotes the vibration of air and affects the frequency response and sensitivity directly. Its performance depends mainly on the manufacturing material, shape and manufacturing process. The material for making vibration film requires the quality of unit area as small as possible, the mechanical strength is high, and the internal damping is large. The mechanical strength of the higher quality, more effective and more broad frequency range of light, the higher the output sound pressure level; damping, The distortion is small under the large signal. Now the diaphragm use polyester film easy hot forming, light weight, good rigidity, some companies have developed new materials for membrane, such as SONY, from Acetobacter isolated cellulose manufacturing "bio membrane" for its senior headset and earplugs, excellent high frequency. The vibration film is usually round, the center is designed as a convex arc shape, and the reinforcement is designed around it, which can strengthen the rigidity of the vibration film and increase the effective area of the vibration film. Sometimes a small hole is machined in the non vibrating part of the diaphragm for the purpose of air pressure balance. High on the manufacturing process requirements of membrane, in the process of a strict control of various. The voice coil is the vibration source of the moving coil earphone, and most of the parameters of the earphone, such as impedance, sensitivity, rated power and so on, are related to it. The performance of the voice coil depends mainly on the material used and the number of turns of the voice coil, that is, the length of the voice coil wire. The voice coil material is generally copper enameled wire, advanced headset is often used copper enameled wire and copper clad aluminum enameled wire, which has the advantages of copper enameled wire, but lighter, but also the use of silver as a coil material. The cross section of the enameled wire of the voice coil is mostly round, and there are triangles and regular hexagon sections, so that the line is more compact, the capacitance between the lines decreases, and the quality of the voice coil is further reduced. The size of the voice coil also has some influence on the performance of the headset. The voice coil is vibration in the magnetic gap, the diameter should be located in the magnetic gap of the voice coil in the central, not with the vibration plate and pole collision. On the other hand, due to the magnetic gap in the surface of the plate is not uniform, the coil is moved in a non uniform magnetic field will reduce the electric energy conversion efficiency, and cause the distortion of the headset, so the voice coil height should have a proper choice. The acoustic structure such as cavity and aperture is an important part of the performance of headphones. The fixed magnetic circuit system and the vibration system are a plastic frame, called the mesa, and the edges of the diaphragm are glued to the frame. The frame should be rigid enough, not because of the deformation of the fixed magnetic circuit and the vibration part, as well as the transmission of vibration as little as possible. The back of the magnetic circuit and vibration system is a headset shell, a cavity is formed between the shell and the table, size, shape, the inner cavity of the damping material of the position, type and quantity of headset frequency response, the more general low-frequency cavity easy to obtain high quality, diving.