The voice coil is the central part of the loudspeaker vibration system. After being energized, it becomes an electromagnet. After acting with the permanent magnet, it drives the diaphragm forward and backward along the axial direction and statically. The length of the stroke of the voice coil, the force, the speed and so on will affect the sound quality.
The voice coil is basically formed by a winding tube [coil skeleton], a coil wound by a wire, and a lead and a pressure paper holding the lead. In the voice coil task, there will be local electrical energy converted into heat energy, the temperature of the voice coil can reach the "very hot" degree. Therefore, the material of the winding tube is required, and it must be heat-resistant. Aluminium foil is usually used, and the foil itself can also be used for cooling. There are also applications of heat-resistant plastic, fireproof paper.
The wire should not be bare wire. It should be covered with insulating material. The coil is also the power of the loudspeaker size of the choice factor, "burning the horn" is actually burning the voice coil, because the voice coil wire burns through the insulation layer and can not work. The higher the temperature the insulation material can suffer, the greater the function of the voice coil can bear, so the insulation layer becomes one of the crux of the promotion of power. Some loudspeakers mention the application of XXX low temperature resistant coating, which refers to the low temperature resistance of the insulation layer.
The voice coil is suspended in the magnetic gap, and it is in contact with the air, which is a poor conductor of heat. The bearing function of the voice coil is promoted, and the magnetic liquid injected into the magnetic gap can increase the heat dissipation efficiency. Of course, the role of the magnetic fluid is not only heat dissipation, it can also increase the damping, the response speed of the voice coil and the sensitivity of the speaker are all affected.
Usually winding coil material cross section is round wire, because the circular cross section of wire processing is the most simple, but the effectiveness of the round wire is not the highest, can clear the voice coil section said, round wire voice coil will be wasted a lot of the cross section of space, and flat wire voice coil is bigger, the application of space so that it can occupy the same volume, higher electromagnetic transformation, This means that the larger the force and the side force, the more the mastery can be improved. But the original value of flat wire voice coil is very high, because flat wire is difficult to shape.
Depending on the loudspeaker design, the length of the coil can be high or low. In a lot of speakers or loudspeakers in the promotion, we often hear a such a word - long stroke design. Long stroke design is related to the suspension system, but also related to the voice coil, if the coil is not long enough, long stroke static, the coil will break away from the magnetic gap, and fall and the force of the permanent magnet, causing the speaker control force to fall. Long stroke voice coils are often used in small - and medium-caliber woofer designs. The larger stroke pushes a larger volume of air, giving a better sense of low-frequency volume.
There are also differences in wire winding. Around, voice coil can produce single, double, four layer or multilayer, winding method is also level wound and around two kinds, different winding will cause different electromagnetic transformation, inductance will there is a difference, the total length of wires on the voice coil weight will affect, voice coil of gravity will also affect conversion, transformation effect is higher, with the promotion of the high frequency response can also. Here is just a brief mention, if interested, please refer to professional materials.
The conductor material is also different, usually used is copper and aluminum wire, aluminum density is small, high efficiency, but the aluminum wire is difficult to weld, so the emergence of copper clad aluminum wire, that is, in the surface of the aluminum wire to cover the copper film, copper clad aluminum wire better balance the material processing and the relationship between the weight. Many manufacturers do not want to indirectly inform you what is copper cladding aluminum, but refer to a "CCAW", in fact, is the same, but CCAW looks more Western. The copper-clad aluminum wire is often used in headphone speakers because these speakers are sensitive to the weight of the voice coil.