Third-party gyroscopic head tracking is not “Spatial Audio”: the Anker soundcore Liberty 4

From a credulous 9to5Mac review of some new Anker earbuds:

Arriving with active noise cancellation, Anker also backs its Liberty 4 with Spatial Audio support, thanks to the internal gyroscope that helps immerse you in the sound.

From the description on the Amazon product page, titled “soundcore by Anker Liberty 4, Noise Cancelling Earbuds, True Wireless Earbuds with ACAA 3.0, Dual Dynamic Drivers for Hi-Res Premium Sound, Spatial Audio with Dual Modes, All-New Heart Rate Sensor”:

360° Immersive Spatial Audio: As you listen to music and watch movies, the built-in gyroscope and spatial audio algorithm track your head movements to always keep you at the heart of the sound for a completely immersive experience.

From the FAQ on Anker’s product website:

How do I enable Spatial Audio?

  1. Wear the earbuds.
  2. Enter the soundcore app and connect Liberty 4.
  3. Select Spatial Audio. 
  4. Spatial Audio cannot be turned on while sound effects are turned on. 
  5. Select Movie or Music mode to adjust the sense of distance while listening to different types of audio content.

Spatial Audio — the Apple feature — is an OS-level capability for taking true many-channel audio and “shaping” it to mimic the effect that the contours of your ears have on physical sound waves when they reach your head. Thus a sound in a movie that would be directed to the rear right speaker in a theater or surround sound system will sound like it is coming from behind and to the right of you when you are wearing compatible headphone hardware.

In other words, if you wear the Anker soundcore Liberty 4 earbuds, connect them to your iPhone, iPad, Mac, or Apple TV, and watch a movie that contains Dolby Atmos audio — you will not be hearing that movie in Spatial Audio. You will be hearing it in stereo, with the Liberty earbuds (on platforms where the app is available) shaping the waveforms so that they sound like they are originating from a space in front of you rather than the center of your head. No sounds will appear to come from behind you with this technology, as they can with true Spatial Audio.

Dynamic Head Tracking — the Apple feature — is a joining of hardware and software, whereby the source of your audio (your iPhone or iPad) is “aware” of its spatial relation to your headphones. Thus if you turn your head, the audio will continue to sound as though it’s coming from the device, rather than in the direction you’re facing; similarly, if you move the device around your head, the perceived locus of the audio will follow the device.

If you wear the Anker soundcore Liberty 4 earbuds and listen to music on your iPhone or iPad, even with the soundcore app, the experience is less clear to me. I believe that the app may ask permission to read your device’s motion sensors, giving it enough data to cause the audio to always follow the device, but I can’t be sure. In any case, this will not be the system-level Dynamic Head Tracking that is only possible with iOS 15+ and compatible Apple headphones.

It bears repeating that Spatial Audio and Dynamic Head Tracking are two separate things, but now it seems necessary to add that there is no Spatial Audio without Apple hardware, period.

There’s no technical reason that Apple couldn’t make this kind of third-party Spatial Audio compatibility possible, as far as I can tell, but as of yet, they haven’t done so.

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