AudioSync

AudioSync sends your computer's sound to several speakers at the same time: AirPlay, Bluetooth and Google Cast speakers, plus other outputs the Mac can reach. It plays a delayed copy on each local speaker so the rooms line up. It is for people who want one soundtrack across a house or a room, and the project positions it as a free, open-source alternative to Airfoil. The README describes it as a beta, so expect rough edges.

The Mac version needs a Mac with Apple silicon and macOS 15 or later. The DMG is not notarized, so the first launch needs Open Anyway under System Settings, Privacy & Security. Google Cast speakers have no shared clock, so you set the offset for each one by ear and AudioSync remembers it. Audio is never written to disk. The same project also ships Windows and Linux builds.