With the launch of tvOS 12, support for the Dolby Atmos surround sound format is finally coming to the Apple TV 4K. Apple’s streaming solution launched last year with support for the Dolby Vision HDR video format right out of the box, but in the ever-messy array of streaming devices, set-top devices, and competing formats, it couldn’t claim bragging rights as a solution for customers looking for a way to experience their favorite movies and TV shows with the absolute cutting edge in home presentation. As of today, that’s changed.

While Atmos support is a welcome addition for Apple TV, it can still be hard for some customers to understand why they should care about any given surround sound option in the first place. In the case of Dolby Atmos, which first debuted in movie theaters in 2012, that’s even more true than usual. The format only started entering the home-entertainment space four years ago, and consumers may not have had the chance to experience it for themselves. But the number of ways Atmos can be experienced at home is growing rapidly, and the addition of the format to the Apple TV will increase that momentum, at the exact same time the entertainment industry is turning more toward Atmos as its finishing format of choice. Why does it matter? Let’s dig in.

What is Dolby Atmos?

Like most Dolby technologies, Atmos started in movie theaters. Historically, cinema surround sound has used a fixed number of audio channels. For example, 5.1 systems use left, right, and center channels along the front of the theater, plus two rear surround channels and a low-frequency effects channel (the “.1” in 5.1). Newer formats, like the Dolby Surround 7.1 format that the company debuted with Toy Story 3, add additional channels to an audience’s left and right. They’re all more than enough to envelop listeners in audio, but they lack a certain precision: no matter how many speakers are in a theater, sound designers and mixers can only use a set number of pre-established channels.

Dolby Atmos, on the other hand, does away with the concept of fixed channels entirely. Instead, it’s built around the concept of audio “objects.” Each sound is a discrete object that mixers and sound designers can place anywhere inside the theater, including above the audience, via ceiling-mounted speakers. Later, when a film is screened, Atmos then maps that mix to the speakers in a given auditorium to recreate the filmmakers’ original intent. It allows for a degree of precision and creative flexibility that simply wasn’t possible before. The system is also designed to be much more scalable across different theater sizes, as well. In a 7.1 mix, the filmmakers are only working with seven main channels of audio. Atmos, however, can support up to 64 discrete speakers in a theater, each able to serve as its own unique location for a sound.

The result is a sonic experience that actually delivers on the much-hyped term “immersive.” Rain can sound like it’s falling from directly overhead. When a car zooms by the camera, the sound can actually match that movement from the front of the theater to the back. And the larger soundstage allows sound designers to create richer, denser, more naturalistic environments than ever before.

“Sound becomes real emotional, because you’re contacting the characters and you’re moving with them.”

“Dolby Atmos and these immersive sound systems work brilliantly when you can move things through the spaces throughout the room, and you can actually hear them,” supervising sound editor Glenn Freemantle told me back in 2013, about his Oscar-winning work in Gravity. “And also, Atmos then creates this smooth transition around [the theater], and over the top. Like when George is going around and he looks up at the stars. He looks at Earth, and the voice is crisp, and they twist right around and come back out the other side. But it’s seamless. So sound becomes real emotional, because you’re contacting the characters and you’re moving with them.”

Since the format’s launch, Atmos theatrical releases have steadily become more common, especially on big-budget films where the creators are hoping for a flashy theatrical experience. Blockbusters like Avengers: Infinity War, Star Wars: The Last Jedi, and Blade Runner 2049 have used the format, but Atmos has also been used on smaller films like The Boy and 10 Cloverfield Lane, as the technology has grown increasingly omnipresent. Its rapid growth has been particularly bolstered by Dolby Cinema’s partnership with AMC Theatres. The resulting theaters combine Atmos with the Dolby Vision HDR laser-projection system for one of the best moviegoing experiences available.

Atmos in the home

Dolby Atmos started as a cinematic innovation, but like other surround sound formats, it has migrated to the home as well. On the premium end of the spectrum are full-fledged multi-channel home theater setups, complete with ceiling-mounted speakers. But systems like that are costly and out of reach for most consumers, so Dolby has also worked with hardware manufacturers to introduce alternative options into the marketplace.

Standalone speakers and some soundbar packages from companies like Vizio and Samsung try to simulate the full Atmos experience with “up-firing” speakers: basically, speakers that bounce audio off the ceiling to create the illusion of sound raining down from above. The results can vary based on the geography of the room being used, but it’s a viable workaround for those who want to step up from current surround systems. Some TVs from manufacturers like LG also offer a “virtualized” version of Atmos, using their own internal speakers, though at that point, you’re no doubt getting pretty far away from the core concept.

TLDR: Dolby has tried to make sure there are as many hardware options out there to allow customers to utilize Atmos as possible. But speakers don’t matter unless consumers own a device that can actually spit out Atmos audio in the first place — which is where tvOS 12 comes in.

Though Blu-rays have been a logical destination for Dolby Atmos releases, streaming services have become increasingly aggressive adopters of the format. Netflix and Vudu offer some content in the format, and Amazon Prime recently jumped into the Atmos fray with its new series Tom Clancy’s Jack Ryan. But a streaming service can only be as good as the device it’s being run on, and as with most living-room entertainment options, the effort to optimize audio is dependent on the mix-and-match situation between services, devices, and content capabilities.

My colleague Micah Singleton surveyed the landscape earlier this year, and it’s a mess. The Roku Ultra supports Atmos and the high-dynamic range HDR10 format, but not Dolby Vision HDR. Same with the Amazon Fire TV and Nvidia Shield. The Chromecast Ultra supports all three formats, but it requires users to cast to the device, rather than operating on its own. With tvOS 12, however, the Apple TV 4K becomes the uber-device many home-theater enthusiasts have been waiting for: capable of supporting Dolby Atmos, Dolby Vision, and HDR10 with a variety of services out of the gate, including iTunes, Netflix, and Vudu. It’s now the standalone streaming box that can, in the words of Verge editor-in-chief Nilay Patel, “light up all the lights” on premium AVRs. And with Apple regularly upgrading previous iTunes purchases with the most up-to-date, highest-resolution option possible, it’s a device that will give many customers an Atmos-enabled movie collection if they just install a software update.

The Atmos Ecosystem Play

Most of the Atmos material is coming from theatrical releases that were mixed in the format, with the final mixes made for movie theaters largely transferring over for home use. “The difference between theatrical Atmos and home-entertainment Atmos is just resolution,” sound mixer Andy King tells me over the phone. King has a varied career across film and television, working on everything from the Michael Mann film Blackhat to TV shows like Altered Carbon and his Emmy-nominated work on Westworld. “The theatrical Atmos is more scalable, meaning the movie theater, depending on the budget that they have for their Atmos setup, they’ll install more speakers in the cloud space and around the room.” Atmos home installations, on the other hand, simply use four ceiling speakers configured like a traditional 5.1 or 7.1 setup. “The resolution isn’t as much as a theatrical, but the print masters we create for Atmos theatrical [releases] do downmix to home entertainment.”

“It folds down really, really well from theatrical to home entertainment.”

Part of Dolby’s larger strategic play is to make Atmos the default finishing format for filmmakers, by making it easy to translate those mixes into the various other formats required for media distribution around the world. “It folds down really, really well from theatrical to home entertainment,” King says, “and then to the other deliverables, being the traditional 5.1, or a 2.0 LtRt [matrixed surround mix], or a 2.0 stereo, or even mono. Dolby’s done their homework, and I, as a mixer, am confident in their technology, and I can convey that to producers and showrunners alike when we get into the home entertainment space.”

That strategy seems to be working. Netflix’s Altered Carbon is an Atmos title, and King also mixed the most recent season of Westworld in Atmos — even though the initial HBO broadcast doesn’t even support the format. (The Atmos mix will be available on the Blu-ray release of the season later this year.)

“It’s a great format, because like on a show like Altered Carbon and even Westworld, there’s a lot of design elements, meaning tones, and things that actually are almost more musical and have harmony to them,” he says. “It’s a challenge when you have those sound design elements for dream sequences, or stylistic sequences, to get them to play nice with the music. The one thing Atmos lends is space, so if we were doing a 5.1 mix, you run into the challenge of putting those elements either in the screen channels or in the surround, and you may run into conflicts with the music … I think Atmos lends itself to be able to make a lot of that stuff live and exist without having to remove it.”

The broader soundstage the format provides also allows filmmakers to approach the sound work in a much more active, dynamic fashion, enhancing the cinematic feel of many modern television shows with audio to match. “In a show like Westworld, there’s not a lot of big sci-fi spaceship moments that you would have in a big action sci-fi movie,” King explains. “You’re out on the plains, or you’re out and about in the park, or even on some of the interiors, [and the] ambiences come alive. I like to mix very live. Whether it be a 5.1 or an Atmos mix, I like to pull elements off the screen as much as I can and utilize the surround. Atmos is fantastic for that, so I can really pinpoint things, and have movement so that the audience member feels like they’re in the experience.”

That’s a combination of factors at work, all of which make it an exciting time for high-quality presentation in the home. Over-the-top streaming services, which are able to move much more nimbly in adopting newer formats compared to their broadcast counterparts, are finishing their original film and TV shows in premium formats like Atmos to distinguish themselves. More theatrically released films are embracing Atmos, providing for another incoming stream of content. And with a device like the Apple TV now in play, a turnkey solution for all premium formats is simpler to get than ever.

Many TV viewers will probably be just fine with watching traditional stereo sound, of course, but as with a lot of format adoption, momentum is half the battle. As of today, Dolby Atmos is one step closer to hitting stride for mainstream consumers.