Mac Multi-Output Device: how to set it up, and why speakers still echo

A guide from Acoustic Orbit.

I build Acoustic Orbit, a Mac app that plays the speakers you already own as one system. Here is the plain answer first. A Multi-Output Device sends the same audio to several speakers, and Drift Correction keeps their sample counts aligned. Neither one measures how long each speaker takes to make sound. So a fixed delay, such as a soundbar fed through a TV, stays as an echo. A Bluetooth speaker's delay also wanders, and nothing in macOS corrects that.

Why the speakers play at different times

Your Mac sends the same audio to every speaker in the group. After that, each speaker takes its own time. A Bluetooth speaker buffers the sound first. A soundbar fed through a TV adds the TV's delay. A speaker across the room adds the time sound needs to cross the air. A Multi-Output Device measures none of this.

Drift Correction resamples a device so that its sample count follows the Primary Device. That keeps the counts aligned. It does not measure when the sound reaches your ears.

I measured this on my own setup in October 2026. A USB speaker (a JBL Flip 7) and the MacBook's built-in speakers were sample-locked to one clock. The microphone still timed the raw acoustic arrival at 57.0 ms for the USB speaker and 0.0 ms for the built-in speakers. A shared clock keeps the sample counts aligned. It cannot tell how long a speaker takes to turn a sample into sound. That capture came from Acoustic Orbit running on my setup, not from a Multi-Output Device.

Three different problems hide behind the words out of sync. They sound different, and only one of them is what Drift Correction fixes.

• Drift. Each device runs on its own clock, and no two clocks match exactly. The sound slides apart over time. Drift Correction targets this one.
• Fixed offset. One path is later by the same amount every time. You hear a steady echo. Drift Correction does not touch it.
• Wander. A Bluetooth speaker's delay is large, and it changes while you listen. The echo moves. Nothing in macOS corrects it.

How to set up a Multi-Output Device

A Multi-Output Device plays the same audio on every speaker you tick. An Aggregate Device is a different tool. It joins several devices into one device with more channels. For several speakers playing the same music, use a Multi-Output Device.

Do the steps in this order.

• Connect every speaker first. Pair Bluetooth speakers in System Settings so macOS lists them.
• Open Audio MIDI Setup. It is in the Utilities folder inside Applications.
• Click the plus button at the bottom left of the device list. Choose the option that creates a Multi-Output Device.
• Tick the box beside each speaker you want in the group.
• Set Primary Device to a wired or built-in output; the other devices follow its clock. Bluetooth is the least predictable path.
• Turn on Drift Correction for every other device.
• Check that every device uses the same sample rate.
• In System Settings, under Sound, choose the Multi-Output Device as your output.

Other free fixes, and where they stop

A Multi-Output Device does not give you a working volume control, so set each speaker's level on the speaker itself. Audio MIDI Setup also has no setting that delays one speaker. A steady offset has no fix there.

Start by listening. Play a clap or a click track from your usual seat, and decide which of the three problems you have. Then try the fixes below. A mix of Bluetooth, a soundbar and a laptop is harder, and nothing in macOS corrects wander.

• Place the speakers at similar distances from your seat. Sound crosses a room slowly, so the nearer speaker is heard first. This cannot fix a delay inside a speaker.
• Prefer wired paths. They are usually steadier than Bluetooth. They are not identical, though. In my capture the USB speaker still arrived 57.0 ms after the built-in speakers.
• Some speaker makers let you link two of their own speakers. Check the maker's manual. A link like this does not bring in the laptop or a speaker of another make.

What Acoustic Orbit does about it

Every speaker you own, playing as one. The soundbar, the Bluetooth speaker, the laptop, the phone in the drawer. One microphone, one clock: wired and Wi-Fi to about a millisecond, Bluetooth compensated and graded for video.

Ask once and a microphone times the room. No receiver. No new speakers. They don't even have to match. Two devices are free for as long as you like.

These are the limits. The about-a-millisecond figure covers wired and Wi-Fi. Bluetooth is compensated and graded for video, and Bluetooth speakers take what Bluetooth allows. It works with wired, USB and Bluetooth speakers, a Raspberry Pi for HDMI, and an Android phone as a speaker. No iPhone or HomePod yet. It needs an Apple silicon Mac on macOS 15 or later, with a microphone (built in on laptops and iMacs; a USB one on a Mac mini or Studio).

Acoustic Orbit: what it does, the price (two devices free).