Spatial audio & Dolby Atmos
Learn how – and why – you should work with this increasingly usable system
> We understand the world of stereo: the audio signal consists of two channels, and then differences in level between one signal appearing in both channels create the impression of the sound appearing from somewhere between the two speakers. Those levels can be changed and adapted, and a sonic object can be made to appear in any place along the line, or indeed move around it.
Dolby Atmos take this further. The concept is simple enough: instead of having just two speakers as in a stereo setup, or five speakers and a sub as in a 5.1 surround sound system, Dolby Atmos allows you to play back over whatever system you do have, and will decode the same signal differently, but with compatibility, which means that you can play a full-range Dolby Atmos mix both over a theatre setup or simply by using those two speakers in a home stereo formulation.
A Dolby Atmos setup is denoted by three numbers. While a classic surround setup may be called, say, “7.1”, standing for seven speakers and a subwoofer, one example of a DA setup could be “7.1.2”, allowing for two speakers placed as a stereo pair above the listener. So how does compatibility work with the system? And what’s going on behind it?
HOW IT WORKS
Because Dolby Atmos will play back based on whatever speaker formulation the listener is using, the way it’s handled by a mixing engineer must be all-encompassing, allowing room for translation. The way it’s done is by mixing in a 360º ‘dome’ around the listener.
As shown in the tutorial on the following page, panning can be done using the Dolby Atmos Music Panner plugin, which allows sounds to be placed anywhere in a 360º circle, and to allow for their elevation as well. With the Panner plugin finished with over a full project, the positional values of each instance can be encoded, and then on playback an opposite system will decode these into audio signals that meaningfully convey the position on whatever the listener’s system is using.
As for the console (or, more likely, the virtual-console) workflow, a typical Dolby Atmos project will have 64 channels, although 128 are possible. A ‘Bed’ is an output channel that corresponds to a single speaker in a particular Dolby Atmos system that the engineer is using to play the project back. In our tutorial project, these Beds take up ten channels: seven for the head-level speakers, one LFE channel, and two top-front speakers above the engineer.
The remaining 54 channels are taken up by ‘Objects’. Each of these Objects is a pair of channels that can be given its own positional information. Using the Dolby Atmos Music Panner plugin, you can choose positional locations (or movements) for each of these different Objects, and their signals should, when encoded, then reach the Beds in the correct amounts.
> 2022 marks a decade since Dolby Atmos first appeared in cinemas – the premiere of Brave in LA being its first outing in 2012. The technology uses a 128-channel system to deliver a totally immersive experience through multiple speaker arrays at an increasing number of your local Odeons.
One of the main benefits of Dolby Atmos is its ability to decode these 128 channels and deliver an Atmos mix through everything from a more typical 7.1.4 speaker setup – seven speakers around you at ear level, one sub and four speakers above you to give you an impression of height – through to a set of headphones.
This flexibility means that the world of music production is waking up big time to Dolby Atmos and an increasing number of recording studios, including London’s Dean Street, now have Dolby Atmos rooms. But it looks like Apple will be the ones credited for bringing Atmos to the masses. You can enjoy Dolby Atmos through Apple Music where songs mixed in it can now, as Apple say, “feel as though they’re happening all around and above you”.
Artists including The Beatles (Lucy In The Sky With Diamonds) and Billy Eilish (Ocean Eyes) have some of the best examples so it’s certainly being adopted by the big guns. Now, though, with the release of Logic 10.7, the world of Dolby Atmos is very much open to producers of all levels, and as our tutorial proves, anyone can mix in Dolby Atmos…