Bluetooth adds its own delay: sound takes a little longer to travel from the Mac to a Bluetooth speaker than to your AirPlay rooms. Left alone, that speaker plays a fraction of a second behind the others, and in a multi-room mix you hear it as an echo. Audiout fixes this with a timing offset, called a trim. A guided wizard finds the right trim, either by listening through your Mac’s microphone or by asking you which speaker you heard first.
Starting the wizard
Two ways in:
- Right-click the Bluetooth speaker’s row in the mixer and choose “Align by ear…”. The same item exists on the Mac’s own row.
- Click the row’s SYNC chip while it’s still untuned.
The wizard needs a license. After the free trial ends, these doors show a note instead (see Audiout only plays on one speaker after the trial).
Measure on this Mac
If your Mac has a built-in microphone, the window leads with “Measure on this Mac”. Press Start, and macOS asks for microphone access the first time. Each speaker then plays a low tone that slides down over a soft chord, one after the other, while your Mac times them. A progress bar shows while it listens. Keep the room quiet.
Every other speaker goes quiet during the run, a Chromecast included, and comes back when it ends. The speaker under “Compare against” can’t be changed once you press Start.
If the reading is too weak to trust, the wizard says so and offers “Try again”, which listens once more. If that fails too, it moves on to the by-ear questions below.
Align by ear
The by-ear path plays a short sound from each speaker, then asks “Which clicked first?”. When the two speakers are different kinds, one plays a higher note and the other a lower one, and the window tells you which is which. Tap the speaker that sounded earlier, or “Both at once” if you can’t tell them apart. Each answer narrows the trim down, until the rooms stop echoing each other.
Expect about 15 rounds. It goes quickly, because you’re only ever answering one question. If you mis-tap, “Undo” takes back the last answer. “Stop” ends the whole thing.
A couple of tips for clean answers:
- Sit roughly between the two speakers, or at least where you can hear both clearly.
- Quiet room, no music playing over the top.
- Don’t overthink a round. If they sound together, say so.
Checking the result
When the rounds are done, the wizard plays its proposal: “Listen: the clicks should land as one.” If they do, click “Sounds right”. If there’s still a gap, click “Still off” and it keeps refining. After a microphone measurement that button reads “Try again” and listens once more. There’s also “Set it manually” if you’d rather type or nudge a value yourself.
When you keep a result, the trim is shown on the row, for example “247 ms · kept”. “ms” is milliseconds, thousandths of a second.
Fine-tuning later
The trim isn’t locked in. Click the row’s SYNC chip any time to open the drawer and nudge the value. Rooms change: move the speaker, and the timing that sounded right before may drift.
If it can’t get a clean reading
Sometimes the answers don’t settle on a value, usually because the room was noisy or the clicks were hard to tell apart. The wizard says “Your answers aren’t settling on one value.” and offers to try again. Fix what you can (quieter room, better listening spot) and run it once more.
Related
- Why Bluetooth and Cast speakers behave differently: What works with each kind of speaker
- Where the SYNC chip sits in the row: The mixer: Main Audio, faders, and meters
- All articles: support overview