Usually you don't need to buy a sound card for 5. 1 channel. The AC97 sound card that comes with the computer motherboard can fully support 5. 1 channel or 7. 1 channel as long as the sound card driver and application software are installed correctly.
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5. 1 channel is divided into pre-recorded and games. Pre-recording has been widely used in various traditional cinemas and home cinemas. Some well-known audio recording compression formats, such as Dolby AC-3 (Audio Coding 3, Third Generation Audio Coding) and DTS, are based on 5. 1 sound system.
5. 1 Outputs sounds in five directions: left (L), middle (C), right (R), left rear (LS) and right rear (RS), which makes people feel like they are in a concert hall. These five channels are independent of each other. The ".1" channel is a specially designed subwoofer channel, which can generate subwoofers with a frequency response range of 20 ~ 120 Hz.
Baidu Encyclopedia -5. 1 speaker