3 AirPlay 2, HomePod Stereo
AirPlay 2 allows for multi-room audio playback. Now users are able to play music in individual rooms, or in different rooms simultaneously.
Users can now ask Siri to play music in whichever room they’d like, as long as those speakers support AirPlay 2.
iOS 11.4 also adds HomePod stereo support, meaning HomePods can be paired together for multi-channel audio playback.