What's the difference between 2.1 and 5.1 channel theater systems?

[podguy]

From what I've read, these are the two main options for surround sound home theater. Is it all just the number of speakers and the number of zeros in the price?

[Jennifer · Accepted solution]

That's one way to look at it. It's all about the number of channels.

A basic stereo system (2.0) has of two channels -- right and left -- produced by stereo speakers and typically powered by a stereo receiver or amplifier.

A 2.1 channel system adds a subwoofer to the two stereo speakers. In a home theater system, there's usually a surround sound decoder that creates the sense of sound coming at your from all directions.

A 5.1 system has 5 or more channels of sound. In order to get this, you need an A/VR (Audio/Visual Receiver) to separate the channels and direct them to the appropriate speakers. The five-point-one channels are left and right, like a stereo system, a center channel for movie dialog or music vocals and on-screen sound, and left and right surround channels, for special effects and surround sound. An additional subwoofer channel adds very low bass for music sources and special effects on DVD movie sound tracks. The five main channels plus the subwoofer channel produce a “soundfield” that wraps you with sound coming from in front of and behind you.

But there's more!

6.1 channel systems have an additional rear-center channel speaker for a total of three front and three rear speakers for more precise positioning of sound effects. The sound of an airplane flying overhead is so realistic you want to duck.

And then there's the seriously powerful 7.1 channel system. 7.1 channel receivers have three front channels, two surround channels and two surround-back channels, plus a subwoofer channel. This is the closest you'll come to the true theater experience of sound coming at you from every direction.

[Mells]

I read something recently about getting surround sound out of a 2.1 channel system.

If you don't want to spend the $$$ for a beefier system, you can get surround sound without rear channel speakers. Some 2.1 Channel systems use special decoders to create the illusion of  multichannel surround sound effects using just the two front speakers and a subwoofer. Basically, it's a 2.1 channel system using  5.1 channel decoders combined with special digital circuits that simulate the sound of rear channel speakers. This review I was reading said it was so convincing that you'd turn your head when you heard a virtual sound coming from behind you.

Sounds like a nice compromise between $$ and sound.