What Do 2.1, 5.1, or 7.1.4 Mean?
Looking at the numbers, it’s easy to feel a little overwhelmed, but these numbering schemes are relatively simple. The first number means how many normal audio channels there are, while the second number denotes how many subwoofer channels there are.
Imagine a simple stereo setup with an A/V receiver connected to two bookshelf speakers. This would be a 2.0-channel system. There are two normal speakers and no subwoofer, hence the 0 in the second part of the number.
A simple home theater system may be 5.1-channels. This denotes five standard speakers and one subwoofer. More specifically, you have a single center channel speaker, left and right stereo speakers, then left and right rear surround speakers, with a subwoofer for extra bass.
Dolby Atmos and DTS:X aim to bring variable height to sound with upward-firing speakers. These get their own number tacked on to the end. A 5.1.4-channel system would be exactly as described above, but with an extra four speakers facing the ceiling.
It’s worth noting that just because a given audio system has a certain number of channels, that doesn’t mean that it has exactly that many speakers. It’s often the case that the numbers match, but not always. A soundbar, for example, may claim 5.1.4 channels but could have as many as 20 or more individual speakers built-in.
While Bluetooth speakers are generally a single unit, that doesn’t mean that there is only one speaker. This is true for some speakers, but even deceptively small-looking speakers may have multiple audio channels.
Stereo: 2.0 and 2.1 Systems
Outside of mono, which is a single channel of audio, stereo is as simple as you can get. If you have a hi-fi stereo system for listening to music, it’s most likely a 2.0-channel system.
That said, subwoofers are getting more popular these days, even for stereo setups. The vast majority of music sold or streamed is in stereo with no subwoofer channel. Instead, the subwoofer carries the low-end information, giving you more bass.
While stereo is most often used for music, it’s fine for a modest home theater system as well. This is especially true if you’re mainly watching TV shows. Services like Netflix offer many of their shows in 5.1 surround sound, but TV shows are mixed with stereo sound in mind much more than movies are.
The benefits of a 2.0 or 2.1 system mainly come down to cost and space-saving. These are cheaper than systems with more speakers, and fewer speakers means less space required. This is great if you have minimalist tendencies or live in a smaller apartment and want to save on storage real estate.
Surround Sound: 5.1, 7.2, and 9.1
If you’ve been to a movie theater, you know what surround sound is. Helicopters seem to circle around the room, sounds come from behind you or to your left or right. Home theater systems can start at as low as 3.1-channels (left and right speakers, plus a center channel and subwoofer), but the vast majority start at 5.1 and go up from there.
A typical 5.1-channel speaker setup relies on the left and right stereo speakers for the vast majority of movie or TV audio, with dialogue coming from the center channel speaker to make it easier to understand. Two surround speakers off to your side or behind you add to the immersion.
Add another subwoofer, and this becomes a 5.2-channel setup. This allows for front and rear subwoofers, or left and right. This helps even out the bass response, so it doesn’t only come from one part of the room. You’ll also occasionally find 6.1-channel systems that add a rear center channel speaker.
A 7.1 or 7.2-channel system is close to a 5.1-channel setup, but with the addition of dedicated surround and rear surround speakers. This means that you’ll hear sounds off to your left and right as well as behind you, bringing it closer to a movie theater experience.
Going beyond 7.1 or 7.2-channel systems puts you into a territory where your home theater is more or less an actual theater in your home. This is because a 9.1 or 9.2-channel setup is similar to a 7.1 or 7.2-channel setup, but with an additional pair of speakers mounted in the ceiling. If you’re going this far, you’re probably pairing it with a projector and theater-style seating.
For the vast majority of people, the sweet spot is somewhere between 5.1 and 7.2 channels. This is still relatively affordable and gives you immersion. To get results beyond this, you’ll probably want to opt for a Dolby Atmos / DTS:X setup.
RELATED: How Do “Surround” Soundbars Work?
Dolby Atmos and DTS:X 5.1.4 and Beyond
As mentioned above, both Dolby Atmos and DTS:X add height to surround sound with either ceiling-mounted or upward-firing speakers. Upward firing speakers built into either a soundbar or your existing surround speakers is the most common way you’ll see this implemented.
Atmos is compatible with any other surround sound system, generally with four upward-firing speakers. Common speaker layouts include 5.1.4, 5.2.4, and 7.2.4-channel systems.
To clarify, a 7.2.4 channel system includes a total of 13 channels. You get a center channel, left and right speakers, a pair of surround speakers, and a pair of rear surround speakers, complemented by a pair of subwoofers. The four upward-firing speakers are built into four of those speakers, usually the front left and right and rear surround speakers.
Atmos isn’t limited to home theater speakers. You’ll find it built into soundbars and other speakers as well. It’s becoming so common, you can even use Atmos surround sound in Windows.
