Winding height and weight of voice coil
The winding wire of the voice coil is wound on the bobhin. The width of the winding part is called the winding height (or winding width). The decisive effect on the performance of the voice coil is the winding height and quality of the voice coil.
A. The coil height of the voice coil
In the size of the voice coil, the height of the coil has a decisive influence on the performance of the voice coil. It is usually the force that the voice coil bears, which is represented by Bli below. For this reason, the factor of a proportional coefficient (Foce Fator), In the vibration of the voice coil, the BL often maintains a certain degree, so the winding height of the voice coil has a very important relationship with the thickness of the upper plate (Plate). Taking the volume of the voice coil as tv and the thickness of the iron sheet as tp, there are three relationships between tv and tp:
① tp=tv ② tp>tv ③ tp
When considering tv>tp, because there is actually magnetic flux in the magnetic gap, there is also magnetic flux outside the magnetic gap, so this point must be taken into account in the design.
It can be seen from the above that the winding height of the voice coil is determined by the amplitude, and the relationship with the audio output is as follows:
∑: amplitude; a: effective vibration radius of the speaker; Pa: sound output; f: frequency
Ⅰ) When tp=tv, current is passed through the voice coil, and the motion of the voice coil causes the volume tv' of the voice coil in the magnetic gap to change, that is, tv'/tv≠1, so the force factor changes. It is impossible to avoid distortion.
Ⅱ) When tv<tp, the coil width of the voice coil lies in the thickness of the iron sheet. When the current-carrying voice coil vibrates, if the amplitude is less than 1/2 (tv-tp), the coil height in the magnetic gap does not change. The force factor has not changed, so there is no distortion. Therefore, usually the winding height of the voice coil is determined according to the relationship between the vibration amplitude and tp. This is based on distortion as the main condition. If the efficiency of the speaker is used, according to the efficiency η=Pa/Pe formula, Pe is the power input; η is For efficiency, Pa=η. Pe, so the amplitude is determined based on the effective vibration radius, frequency, efficiency and input power of the speaker. As for the so-called wide voice coil method, a wider voice coil with a high winding height is used for the purpose of reducing fo as much as possible. From the above formula, it can be seen that the amplitude is the inverse ratio of the frequency multiplication, and the period where fo is located. As the amplitude increases, it is necessary to increase the winding height of the voice coil according to the requirements of the amplitude. However, it should be noted that the part where the magnetic flux intersects with the winding wire height is reduced due to the increase of the winding wire height, so there is a tendency to reduce the efficiency.