https://www.theverge.com/2018/5/29/17403684/airplay-2-ios-114-stereo-homepod-available-now

iOS 11.4 is available today, and it comes with two notable new features: Messages in the Cloud and AirPlay 2. We’ll dive into the messaging update in another post, but AirPlay 2 is a big deal: it adds multi-room support so multiple AirPlay 2 devices from a wide variety of manufacturers can all play the same music around your house, and it allows two HomePods to play as a stereo pair. All together, AirPlay 2 brings Apple’s wireless audio system to parity with competitors like Google Cast and Amazon Alexa after years of stasis. Seriously: this is the biggest update to the audio side of AirPlay since it was first announced as “AirTunes” in 2004.