Loudspeakers can be divided into many types according to their size, usage and usage, each with its own advantages. Portable loudspeakers are limited by their size and shape as well as their horns, and their general power is only 3-8w. And wireless microphone and wired microphone are different in size, use different, smaller size suitable for teachers, tour guides to use, hanging in the waist, so that the hands play more freely, its power is generally in the 3w-8w. The large size is suitable for outdoor activities, summer camp, extracurricular speech and other places with large flow of people, and the power is 35W-- 95W. Li-ion amplifiers are classified according to the type of battery they use. It solves the problem of environmental pollution caused by traditional dry battery. It mainly USES lithium battery technology of mobile phone to power the amplifier.