Dolby Atmos: Spatial Audio From the Cinema to Your Headphones

Dolby Atmos is essentially the “name brand” spatial audio format. It’s a way to more convincingly create surround sound in the cinema and at home. How it works, and how well it works, will vary depending on the situation. The Dolby Atmos logo can be found on everything from movie theaters to TVs to headphones, and in the best use cases, it can create an immersive 3D sound field that augments the visuals on screen. 

In its most elaborate form, typically in high-end cinemas and home theaters, Atmos uses height speakers to create a verticality to the sound. These speakers are typically mounted high on walls, or in the ceiling, while some setups use upwards-facing drivers to bounce the sound off the ceiling. Atmos can also be combined with head-tracking technologies in headphones, and using other processing techniques in tablets and phones. 

Because Atmos covers a suite of different technologies, it can be a bit confusing. Here are a few highlights:

• Height channels can create a more immersive sound.
• The best sound will be with a multispeaker setup, but even soundbars with Atmos offer a much “bigger” and more enveloping soundstage than stereo bars.
• Ceiling speakers are great, but many companies sell upward-firing speakers that will come close in performance without the need for speaker mounting or installation.
• Head-tracking in headphones is liked by some, but considered gimmicky by others.

To understand what makes Atmos different from, say, its direct predecessor Dolby Digital, let’s first take a look at how sound is mixed for movies and TV shows.

Making sound surround

Everything you hear in a movie, from the music to the voices to the sound effects, all gets mixed into specific “channels.” For simplicity’s sake, we’ll say these channels are, as you look at them in a room, left front (L), center (C), right front (R), right surround (RS) and left surround (LS). Some more complex systems add “surround back” channels. All the low-frequency booms and thumps go to the “.1” subwoofer channel. This diagram should help:

So if two actors are speaking onscreen, that gets mixed to the center channel. When the music swells during a dramatic moment, that’s usually in the front left and right channels. Zooming and swooping special effects might appear in the surround speakers. To an extent, this same mix of channels also translates to the home. After all, if you have a 5.1 speaker system, you have all those same speakers.

Except… you don’t. Not exactly. Where your speakers are, how powerful they are, and increasingly, how much range each has, varies greatly compared with a decent movie theater.

At the mixing stage, Dolby Atmos doesn’t use channels. Instead, most sounds are treated as “objects.” Instead of assigning a sound to a channel (and by extension, a speaker), Atmos lets filmmakers assign a sound to a place. Not “left surround speaker” but “left rear corner.” Not “pan from left surround speaker to right sound speaker” but “pan smoothly across the rear wall.” Not only does this give greater flexibility, but it improves the experience in the theater and, potentially, at home. 

Atmos is an end-to-end change in theater and home audio. The mixing is different, as we’ve discussed, but so is the decoding. At different theaters, the number of speakers can vary dramatically, but Atmos will scale with them regardless. Most theaters have many speakers along the walls to ensure everyone gets a similar experience. With Atmos, those speakers can be individually addressable and a sound designer can pinpoint the exact location in a theater where they want to place a sound. A smoother experience for everyone and this is represented in the image above.

The ability to place sound anywhere naturally includes the headline Atmos feature: height. With speakers hanging from the ceiling, sound engineers can now move sounds seamlessly over your head and all around. Done right, it’s not only more convincing than before but also less obtrusive. It’s more natural, so you’re less likely to notice the special effects and more likely to stay absorbed in the movie. That’s the point, right?

So what about the home?

Theaters are great and all, but most of us watch movies and TV shows at home. All the big-name streaming services, like Apple TV+, Amazon Prime Video, Disney+, Max, Netflix, Paramount+ and Fandango at Home (nee VUDU), have movies and TV shows with Dolby Atmos. Not every movie or show will have Atmos, of course, but increasingly most will. Typically the Atmos logo will be somewhere obvious in the show/movie description. 

Dolby has been branching Atmos out into music as well. Apple Music, Tidal and Amazon Music Unlimited offer a selection of titles which been mixed in Atmos.

To let mobile users experience both Atmos music and movies, many newer mobile devices have a version of the technology called Dolby Atmos for Headphones. Although those are stereo-only, they’re designed to simulate Atmos effects with any headphones. The tech is available for Xbox and PC as well, for $15, via the Dolby Access app, which also adds Atmos to some games. In addition, many AirPods models now enable Atmos as part of its spatial audio technology.

If you’re listening at home, though, let’s get this out of the way first: Most people aren’t going to install height speakers in their ceiling. That’s fine because there are a growing number of speakers and soundbars that either feature built-in height channels or fit on top of existing models. In the case of a standard tower or bookshelf speaker, you can fit a speaker model on top that has a separate, upward-firing driver. These speakers bounce sound off the ceiling to mimic “real” height speakers. I’ve heard quite a few of these and they work surprisingly well. Not as well as real height speakers, of course, but it works and is a far simpler option if you aren’t interested in installing speakers in or near the ceiling.

If you want to take advantage of true Atmos surround you’ll need new hardware. Dolby Digital is still the default for everything, so this isn’t a required upgrade. If you’re not interested in Atmos, your gear will still work. Even if you get a brand-new 4K streamer to connect to your older receiver, the audio will still work if it doesn’t have Atmos. It will just play a Dolby Digital or Dolby Digital Plus track.

If you want height channels, more channels or other benefits of Atmos, then you’ll need a receiver or soundbar that can decode it and a source that provides it. (Those sources include 4K Blu-ray players, newer
media streamers
and some game consoles.) You’ll need Atmos content, which we’ll discuss in a moment. 

To the right, you’ll see a couple of Atmos home setup examples. At the top, you see a setup with specially designed upward-firing speakers. Each is a traditional speaker but also has separate drivers that shoot sound to bounce off the ceiling. These are tuned so the bounced audio sounds correct to your ears. At the bottom, you see a soundbar designed to do the same. 

Atmos also lets you have a greater number of possible speakers. How many could you have if you really wanted to go wild? Just 24… plus 10 height speakers. That’s 34 speakers if you want. You don’t need to do that, but if you’ve got a bunch of spare speakers and amps lying around and a room that can fit them, go for it.

For Atmos, Dolby uses a slightly different twist on the nomenclature of home systems. Traditionally a 5.1 system has three speakers up front, two on the sides or in the back and a single subwoofer. If you then added two Atmos height speakers, Dolby would describe this system as a 5.1.2 system. If you see “a 7.2.4 home theater” you can deduce that it’s probably got three speakers up front, two on the sides, two in back, two subwoofers and four height speakers.

All around

In addition to the gear, you’ll also need Atmos content. That’s actually pretty easy. There are shows and movies on all the major streaming services. For music, there’s Amazon Music Unlimited, Apple Music and Tidal. On disc, Atmos can be found on 4K and regular Blu-ray discs. It’s even in a handful of video games.

Chances are if the movie is 4K, it’s also Atmos — although that doesn’t mean it’s in Atmos everywhere you can find that movie. It might be available with Atmos on the 4K Blu-ray, but not on Amazon, for example, or it could be in the competing DTS: X or Imax Enhanced formats. The thing with Atmos is that it’s also backward compatible, and so if you buy a movie featuring Atmos it will also have an audio track your current gear can play, even if it’s minus the height channels.

Is it worth upgrading all your gear to take full advantage of Atmos? No. It’s cool, but if you’re not a home theater junkie this might be more money than you need to spend if you’re not using it. When you’re ready to upgrade anyway, chances are the gear you’re considering will have Atmos. For example, most of our favorite receivers already work with Atmos, as do several of our favorite soundbars.

Originally published in 2017 but updated regularly with new info about Atmos and spatial audio in general. 

As well as covering audio and display tech, Geoff does photo tours of cool museums and locations around the world, including nuclear submarines, aircraft carriers, medieval castles, epic 10,000-mile road trips and more.

Also, check out Budget Travel for Dummies, his travel book, and his bestselling sci-fi novel about city-size submarines. You can follow him on Instagram and YouTube.