What is the difference between stereo and surround sound?
In: Technology
Stereo is two channels. By balancing the levels of each channel evenly the audio is centered. By adjusting levels to favor the left or right you can create the auditory illusion that the sound is coming from either side and give ‘geographic space’ to the sounds you’re hearing. For example, panning a sound from one side to the other can create the impression that a car is passing by.
Surround sound works the same way but is typically 5:1, meaning six channels ported to speakers that encircle the listener/viewer. By adjusting levels, or simply limiting specific sounds to specific speakers, you can create the illusion that you are ‘inside’ the sound space. Typically the center channel is reserved for dialogue, the sides for sound effects and music, the rear satellite speakers with ambience effects and/or music, and the LFE channel for low end bass effects. Panning effects from speaker to speaker can create the illusion that, say, a helicopter is passing overhead and in a specific direction.
Stereo = 2 channels (usually Left & Right). There are two separate audio tracks, one comes from the left speaker, one from the right.
Surround sound = more than 2…typically 5 or 7. If it’s 5 it’s the four corners plus a front-center (“Center channel”). 7 adds the sides. The .1 (5.1 or 7.1) is a subwoofer. By having more channels and more speakers, you can better control the perception of where the sound is coming from and get a more immersive experience.
There are sophisticated techniques to provide surround-like audio through 2 channels, this is often used with headphones and sometimes on computers. They’re not true surround but they sound better than stereo.
Stereo is sound coming from left and right only. You can’t really tell if the noise on the left is in front of you or behind you, just that it’s left. Surround is left and right, but also front and back.
I’ll go a bit more in-depth.
Stereo: 2 speakers in front of you aimed at you (or headphones).
Surround Sound: Multiple speakers aimed at you and likely a subwoofer or 2.
For surround sound, you add a “center” speaker between the left & right speakers, usually in/on your tv cabinet. The center speaker gets nearly 100% of all the on-screen dialogue and the majority of non-ambient sounds. Your left & right speakers along with surround/height speakers are mainly for playing the soundtrack of a movie, any ambient sounds, and and sounds panning moving around.
A 5.1 means 5 speakers and 1 LFX channel, typically a subwoofer. The 3 main speakers are your left,center,right, the other 2 are your surrounds which go to your sides.
A 7.1 adds 2 speakers behind you.
A 9.1 adds 2 speakers between your left/right and the surrounds.
Then you have height speakers, these are your Dolby Atmos and DTS:X movies. I know we are in a pandemic, but in the future locate a movie theater near you with a Dolby Cinema and see a blockbuster film.
Height speakers are speakers that go in/on your ceiling and some can go on your walls near the top. For 2 height speakers on a 5.1, it turns to 5.1.2, for 4 heights in a 7.1 it’s 7.1.4. These speakers are in specific locations as well. For home use, Atmos can go up to 24.1.10 and looks [like this](https://1sd8cp36yiis47168hvghagm-wpengine.netdna-ssl.com/wp-content/uploads/2016/05/Andrew-Lucas-3D_Audio_configuration-Dolby-Atmos-24.1.10-1.png).
Now, usually when making the audio for a movie, they don’t make a separate version for each combination, they usually make 1 version in Atmos or DTS:X, and then convert it to 9.1/7.1/5.1/stereo, which is one reason why dialogue is hard to hear from a tv, it’s playing >30 channels of audio with only 2 speakers (the main reason though is that tv speakers aren’t good quality).
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