The speakers that support Airplay can proxy Airplay to the others, with caveats: you can group a speaker that's playing Airplay with speakers that don't suppor

The speakers that support Airplay can proxy Airplay to the others, with caveats: you can group a speaker that's playing Airplay with speakers that don't support AirPlay and it'll play back on all the speakers just fine. The big catch is that the speaker that's actually receiving the AirPlay stream has to keep playing it; if you ungroup that speaker, it'll stop AirPlay playback on all the grouped speakers. Not sure whether that's an actual technical limitation or just a limitation in Sonos's UI, though. I wish AirPlay behaved more like Line In does (on speakers that support that), where the Line In devices become available to any speakers on the network.