To talk about what is called an active speaker, it is necessary to talk about the composition of the sound system. The simplest sound system consists of several links: sound source, power amplifier and speakers. Audio source refers to sound broadcasting equipment such as radio, deck, CD player, VCD, DVD, MP3, etc. As far as computers are concerned, both optical drives and sound cards are audio source devices. Generally, the output voltage of audio equipment is relatively small, between hundreds of millivolts and two volts. If the speakers are connected directly, the sound may be very small or even silent.
And because the impedance of speakers is generally very low, most of them are between 4 and 8 ohms. Some speakers with special plans have impedances of less than two ohms in certain frequency bands. They are short-circuited close to each other, which can easily overload the audio source equipment. It may even cause damage to the sound source equipment. Therefore, it is necessary to add a power amplifier (power amplifier for short) between the sound source and the speaker to expand the weak and small signal output by the sound source to a satisfactory power to advance the speaker, so that the speaker declares a satisfactory volume.
At the same time, the power amplifier has a high input impedance (usually tens of kilohms) and a low output impedance (a few tenths of ohms), which can play a buffer effect between the audio source and the speaker, which will not overload the audio source equipment, but also It is easy to advance the speaker. Functional effects Generally, each link of Hi-Fi audio is relatively independent, and a complete audio system can be formed through various connections.