What is the difference between 5.1 and 7.1 surround sound?

In a 5.1-channel surround sound system, you have five+one speakers: front left, front center, front right, surround left, surround right, and a separate subwoofer.

The surround channels, ideally, should be positioned to the immediate left and right of the main listening position. A 7.1-channel system adds two extra channels, left rear and right rear, which should be positioned behind the main listening position.

Michael Miller is a writer and commentator on technology and digital lifestyle topics.