What does fixed Spatial audio mean

Spatial audio is an effect that gives the impression of sound coming at you from three dimensions. It's common in gaming headsets and has been making inroads in other types of headphones, especially now that Apple is offering support for the technology through its latest pairs of AirPods and Beats. But what exactly does it sound like, and what do you need to experience the effect at its best? We've tested Apple's spatial audio across every pair of headphones it works on, and have collected everything you need to know right here.

What Is Spatial Audio?

Spatial audio is an umbrella term for various spatial effects you can experience through headphones or speakers. For headphones, it's a system that adjusts balance and frequency response for different sounds between your ears to give the impression of directionality, in some cases incorporating motion sensors and head tracking in the process.

Specifically for Apple devices, spatial audio is offered in four basic varieties:

• Spatialized Stereo
• Spatialized Stereo With Dynamic Head Tracking
• Dolby Atmos 
• Dolby Atmos With Dynamic Head Tracking

Spatialized Stereo is simply an effect applied to music that wasn't mixed for spatial audio. It takes the stereo channels of whatever you're listening to and puts different processing effects on it, in an attempt to massage some directionality out of the purely left-right mix. It can sound cool, but it can also sound pretty terrible (especially with music), and it's definitely the least impressive type of spatial audio.

Dolby Atmos, on the other hand, is a technology that some music and plenty of films (and some TV shows) are now mixed with. Instead of simply mixing audio to 5.1 or 7.1 channels (the x.1 is the subwoofer, which isn't directional), it maps individual audio sources to different positions in a 3D space around you. It’s meant to provide a much more immersive spatial feel for your home theater, similar to what you get in a theater or live space.

Film is where Atmos has seen the most use, but now artists are starting to mix music audio this way as well. The new James Blake record, available on Apple Music in Dolby Atmos, does indeed sound interesting with the effect turned on (but it also sounds fine with it off, and this is true of most music mixed with Dolby Atmos). The latest version of Apple Logic Pro includes mixing tools for both Dolby Atmos and spatial audio, so you can even make your own spatial music at home.

Keep in mind that Atmos is, at heart, a speaker technology, as speakers such as soundbars use angled drivers and acoustic reflections to facilitate height channels and incorporate additional satellites for true rear and side imaging. By comparison, headphones only have one audio source on each ear (we've seen a few "surround sound" headsets in the past that use individual drivers for different channels, but because headphones have no space for different sound sources to come from, they don't work well).

Spatial audio for headphones attempts to achieve the same sense of directionality through some clever processing and tweaks, but you're still getting a watered-down version of the effect on speakers, no matter what anyone tries to convince you. It may sound cool, but it’s not playing with the same tools a soundbar has at its disposal. 

The head tracking aspect of spatial audio uses motion sensors built into earphones or headphones to actively pan the mix based on how you move your head, to give the impression that all of the audio sources are anchored at specific points around you. It’s perhaps a bit gimmicky, but it works. We've seen this sort of feature before on over-ear headphones and gaming headsets like the Audeze Mobius, Dolby Dimension, and HyperX Cloud Orbit S, but in-ear implementation is new. Adding head tracking to either Spatialized Stereo or Dolby Atmos creates a room-like feel to the audio experience, though you're essentially layering effects (don’t worry, purists, you can simply turn spatial audio off completely).

What Works With Spatial Audio?

For Dolby Atmos content, almost any headphones you can pair with your iOS device will work support it (yes, we many any headphones, not just those from Apple or Beats). In the Music app on your iPhone, enable Dolby Atmos downloads and switch Dolby Atmos to Automatic, and whenever Dolby Atmos mixes are available, you’ll be listening in Dolby Atmos.

For Apple Music, headphones with Apple's H1 or W1 chip automatically play Dolby Atmos audio by default when it’s available. This covers both Apple and Beats headphones, including all AirPods, as well as the Beats Flex, Powerbeats, Powerbeats Pro, and Studio Buds.

The list gets much shorter for spatial audio with dynamic head tracking. These headphones all have one thing in common: Beyond the inclusion of H1 or W1 chips, they have accelerometers that track the movement of your head.

Here’s the list of products you can use with spatial audio and dynamic head tracking as of this writing:

For the latest version of spatial audio, you’ll want to make sure your iPhone is updated to iOS 15.1.

How to Enable (or Disable) Spatial Audio

If you pull up your iPhone's Control Center screen, you should see your paired AirPods (or other compatible headphones) appear where the volume slider is. Press and hold on this slider and a screen appears with three controls: a large volume slider, a noise cancellation switch (for the AirPods Pro), and a toggle for spatial audio.

Spatial Audio will appear as Spatialize Stereo Fixed or Spatialize Stereo Head Tracked (or Spatialize Stereo Off if you're listening to content that wasn't mixed for spatial audio). When you enable Spatial Audio, the icon turns blue, and if the audio you're listening to works with Spatial Audio, the icon will be animated. 

When Dolby Atmos audio is available, instead of Spatialized Stereo, your options will read Spatial Audio Fixed, Spatial Audio Head Tracked, or Spatial Audio Off. A Dolby Atmos icon will appear above these on-screen options when it's in use, and when the effect is off, it will read Dolby Atmos Available.

What Does Spatial Audio Sound Like?

If you want a simple demo of spatial audio, go to your iPhone's Bluetooth menu and tap on the icon next to your paired AirPods or other compatible headphones. A screen with various controls and bits of information about your headphones will appear. Scroll down, and you’ll see not only the spatial audio toggle, but a link to See & Hear How It Works. When you tap it, a demo starts with a chime-and-shaker-driven audio loop in stereo; you're then invited to press Spatial Audio to experience the loop with the effect on.

At first, the audio simply sounds like it’s going through a different type of reverb and EQ filter, but with a little head movement, you'll better notice the effect. Turn your head to the right, and the shaker is in your left ear. Turn to the left, and it ends up back in your right ear. When the shaker is directly in front of you, you get a sense of it being an object in the room, with a real spatial feeling to it, rather than something panned in a stereo mix—it's a cool effect.

Applied to actual music you want to listen to, it’s a crapshoot as to whether you’ll like the effect. And remember, there’s the spatialized stereo aspect of this, and then there’s the additional head-tracking aspect, which are two different effects. Generally speaking, spatial audio is at its best on tracks mixed for Dolby Atmos, with head tracking enabled. On the flip side, it's the least impressive as a spatialized stereo effect slapped on mixes that weren’t intended to be heard that way.

Is Spatial Audio Worth the Hype?

Ultimately, the key ingredient here is Dolby Atmos: When you see that appear on your screen, you know you’re hearing a track that actually was meant to work with spatial audio. Music and audio that was mixed in Dolby Atmos with spatial audio in mind is going to sound more impressive than audio that wasn’t.

When you see Spatialized Stereo, it’s really just applying a processing effect to audio that wasn't mixed for spatial audio.

And finally, it’s important to think of head tracking as an extra, independent effect that can be applied to both types of spatial audio.

At this stage, spatial audio is more of a cool effect than a game changer, but who knows what the future holds? It adds some fun to the listening experience, and it’s easy to imagine the effect working well for games and apps, where the user is driving the narrative. We'll continue to test spatial audio and the products that support it, so make sure to check back again to see how it develops.