it is on the page: "Combine two in one room. Put another HomePod in the same room, and the two automatically detect and balance each other — for sound that’s

it is on the page: "Combine two in one room. Put another HomePod in the same room, and the two automatically detect and balance each other — for sound that’s even more lifelike. AirPlay 2. Add HomePod to more rooms. When you add HomePod to multiple rooms, the speakers communicate with each other through AirPlay 2 — so you can play your music all around the house. You can also control any other AirPlay 2‑compatible speakers."