Play sound through two speakers or headphones at once

Why it happens

Your Mac sends sound to one output at a time, so picking a second speaker switches away from the first. Audio MIDI Setup, a utility that comes with every Mac, can join several outputs into one combined device. Your Mac then treats that bundle as a single speaker and plays to all of them.

How to fix it

1. Connect or pair every speaker and pair of headphones you want to use first, so the Mac can see them.

2. Open Audio MIDI Setup. It's in Applications > Utilities, or press Command-Space, type Audio MIDI Setup and press Return.

   Audio MIDI Setup

3. Click the + button at the bottom left of the window and choose Create Multi-Output Device. A new device appears in the list on the left.

4. On the right, tick the box in the Use column for each output you want. Set Primary Device to the wired one if you have one, as it keeps the others in time. If the other outputs slowly drift out of time, tick the box in the Sync column next to each of them, but not the primary one.

5. Open System Settings, click Sound, and under Output choose Multi-Output Device. Play something to check it comes out of every speaker.

   Sound›Output

Still not fixed?

1. The volume keys and slider don't work on a combined device. Set the loudness on each speaker itself, or select each one in Audio MIDI Setup and change its volume there.

2. If one speaker is a little behind the other, that's normal with Bluetooth, which adds a short delay. Wired speakers, HDMI and USB stay closer together.

3. If a device isn't in the Audio MIDI Setup list, it isn't connected yet. Reconnect it in Bluetooth settings or plug it in again, then reopen Audio MIDI Setup.

   Bluetooth

4. To go back to one speaker, open Sound > Output and click the device you want. The combined device stays in the list for next time.

5. If sound crackles or drops out only on the combined device, remove the Bluetooth outputs and test with wired ones. If even one speaker on its own sounds broken, it may be a hardware fault, so contact Apple Support or a repair shop.