Great audio can provide an extra dimension to films and TV, but it comes with its own language and some very strange numbers.
You don’t have to create a bespoke home cinema to notice the difference, but it is useful to understand what you can do with a few extra speakers.
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Speaker numbers: what is 2.0, 5.1, or 7.1.4 audio?
Home Entertainment Speaker System Sound systems are built up from speakers and channels, and the numbers tell you how many there are, and what kind.
2.0: This is the starting place for good quality sound - a stereo system with two speakers playing left and right channels. It’s still the best for music, just try to keep your two speakers as far apart as possible.
5.1: The default surround sound system has five surround channels - stereo front and back, plus a front centre channel that makes dialogue easier to hear. The “.1” is a low-frequency channel that lets you hide a big bass speaker in the corner for chunky explosions and have smaller directional speakers around the room.
6.1: Home Entertainment Speaker System A centre rear speaker can give the impression that something is approaching or moving away behind you. Great for scary movies.
7.1.4: This would be an ideal system for Dolby Atmos, with seven surround speakers - stereo front and back, left and right. There are four high-up speakers, either set in your ceiling or firing up to reflect down.
[Read more: What surround sound speaker setup do I need?]
Home Entertainment Speaker System
Analogue surround sound: Dolby Surround and Dolby Pro-Logic
The basic idea of watching films with a soundtrack that surrounds us in a realistic fashion wasn’t invented by Dolby Labs, but they brought the technology to cinemas in 1982, and took it into the home as video recorders took off.
Dolby Surround had two stereo front channels and a single surround channel that went to left and right speakers behind you.
It morphed into Dolby Pro Logic and Dolby Pro Logic II, adding more channels, special music modes, and clever effects to direct your hearing and create the illusion of 3D audio, called 'psychoacoustics'.
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Digital surround sound: Dolby Digital, AC-3 and DTS
When DVDs arrived in the late 1990s, they came with surround sound that was as good as you could hear in the cinema: Dolby Digital and DTS.
Dolby Digital (AC-3): AC-3 is the digital encoding scheme used for Dolby Digital sound. When you see an AC-3 badge, it means that the product can take part in a Dolby Digital sound system.
DTS: Home Entertainment Speaker System Mostly used for DVD and Blu-ray, the key difference from Dolby Digital is that DTS has more data, so the sound should be of a higher quality. Some say that it’s only noticeable if you have a very high quality surround sound system in a dedicated home cinema room. DTS was originally invented for Steven Spielberg, who wanted a better surround sound experience for Jurassic Park.
Object-based surround sound: Dolby Atmos and DTS:X
Built In Home Audio Speakers
The latest step forward in surround sound is to treat sound as a stage where people, helicopters and dinosaurs can move around, instead of mixing them together.
AV receivers with Dolby Atmos and DTS:X put these ‘audio objects’ into the correct surround channel and mix ambient sounds like rain into them. It will work differently with a 2.0 speaker system and a 5.1 system.
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If you have dedicated speakers in your ceiling or designed to reflect sound off your ceiling, Dolby Atmos and DTS:X can project the illusion of ‘height’.
Dolby Atmos can have up to 128 objects in any scene, while DTS:X has no limits. For smaller speaker systems and soundbars, DTS Virtual:X uses psychoacoustic tricks to give the illusion of height.
Receivers, subwoofers and soundbars
Home cinema audio needs some special kit that needs explaining.
AV receiver: This is the big black box that turns the signals from your BT TV box, PS4 or DVD player into stunning audio from your speakers. It usually has optical (S/PDIF) and HDMI connectors for your inputs, and various clips, binding posts and sockets for outputs. AV receivers can often also connect to streaming audio services or Bluetooth from your phone.
Subwoofer: Built In Home Audio Speakers LFE (low-frequency effects) or bass sounds need a larger speaker, but people don’t want five big speakers in their living room.
Our ears can’t hear the direction of bass sounds, so the solution is to split them off into a big speaker that’s out of sight, and have smaller speakers for directional sounds at middle and high frequencies.
Soundbar: These revolutionary devices have freed us from needing lots of speakers and wires to enjoy surround sound, though they’re not as good as a full surround system.
Built In Home Audio Speakers Soundbars combine lots of small speakers which bounce sound off your walls to give the illusion of a multi-speaker system. Some of them have a separate subwoofer, while others go for a compromise with a small built-in sub.
Read more: Take a look as we explain the range of audio and video connections