Quote from the article:
“There are two principle ways to produce a surround sound experience. The obvious way is to surround the listener with speakers. This approach has the advantage that it is quite straightforward to implement. To capture the source a certain number of microphones can be set up to record in different directions. Reproducing the original is then a simple matter of playing back the sound recorded by each microphone through a correspondingly positioned speaker. If two microphones are used then a lateral stereo field can be reproduced. If three, four or more microphones are placed in a circle, then a 2D surround sound field can be reproduced. If additional microphones are used that point up and down, then it is even possible to create a 3D surround sound experience. This natural extension to the preexisting stereo technique can account for the success of this surround sound approach.
The second method of creating a surround sound experience is to somehow simulate audio positioning with only two speakers. This is called “virtual” surround sound and we will be looking at that in the next section. ”