What Are Audio Channels?
If you are on a mission to bring high-quality sound to your home, one thing you need to decide on is the number of audio channels that you want to listen to your sound on. What exactly is an audio channel?
An audio channel is the "location" or "passageway" of a specific signal or data in a piece of audio. It can refer to the sound either coming from, or going to, a single point. For example, many songs used to be recorded on a 4-track device. This provided four separate audio channels. Nowadays, multiple channels are often used in digital recordings.
Stereo systems are a common example of a two-channel system. There are usually two speakers (a left and a right), and each has its own unique audio output. One is usually to the left of the listener and one is to the right, and this is meant to reflect the fact that humans hear in stereo thanks to having one ear on each side of their heads. This is a trait that enables us to hear sounds from pretty much anywhere within a certain distance and from almost all angles, and this is probably associated with early humans (hunter/gatherers) needing to be alert to potential dangers. Stereo sound is used at the movies, in televisions, in music players, and by FM radio stations.
What about mono?
Mono (Monaural or monophonic sound) is where the audio signals are routed through a single channel. Mono is less expensive for recording and reproduction as it only requires basic equipment. Despite being less modern and trendy than Stereo, it is still used in public address systems, some hearing aids, telephone and mobile communication, and even on some AM radio stations.
What are the most common setups?
As most systems will have one speaker per channel, you may notice that these two terms are often used interchangeably despite not actually being the same thing.
A basic stereo system consists of two channels of sound - a left and a right that are outputted to two (usually separate) speakers, and could be anything from these Totem Kin Monitor Bookshelf Speakers, to these Borresen Acoustics 05 Floor Standing Speakers. This is a very common setup, particularly in domestic settings. Often people will have one speaker to the left side of the room and one to the right (or perhaps one at each end of a settee). This is usually known as a 2.0 setup/system.
If a subwoofer is added to the standard two speakers mentioned above, the system becomes known as a 2.1 - indeed every system that ends with a “.1” contains a subwoofer. The subwoofer, such as the visually appealing Totem Thunder II Subwoofer, is used to add extra bass and warmth to the sound. It is able to deal more effectively with a low-frequency effects (LFE) channel than standard speakers can. Many sound bars feature 2.1-channel setups. 2.0 and 2.1 systems are the most cost-effective setup and are perfectly adequate for smaller spaces.
Other sound systems
Home theater sound systems tend to involve more audio channels than those for just music.
A 3.1 system involves four audio channels - three speakers and a subwoofer. The left and right speakers deal with the music and sound effects and are accompanied by a central speaker that focuses on the dialogue.
Surround sound is a popular choice for home theater systems. A standard surround sound setup is the 5.1, where six audio channels are mixed together. Five of the channels have full bandwidth and the subwoofer deals with the LFE. The speakers are set up around the room, including behind the viewer/listener. This creates the illusion of people behind you and is great on something like a scene in a movie where the villain is following the hero.
A 7.1 system features eight audio channels in total - heard via seven speakers and a subwoofer. It has two more rear speakers in addition to those found in the 5.1. This offers a fuller and more rounded sound experience.
The next step up is the 9.1 surround system featuring ten channels, including nine speakers and a subwoofer. The two extra speakers in this setup are placed at the front of the room, directly above the main left and right speakers. This is a very high-end surround sound setup.
As a general rule, the optimum number of channels is mostly dependent on the room type, setup, and size. The bigger the room, the more channels you can take advantage of. A lot depends on whether you want the system predominantly for listening to music or watching movies (or perhaps both).