How to Create and Configure a Multi-Output Device on Mac to Play Audio to Multiple Speakers Simultaneously

By default, macOS only allows system audio to play through a single designated output device at a time—either your Mac’s internal speakers, an external USB DAC, a pair of connected headphones, or a Bluetooth receiver. If you want to listen to music simultaneously through wired headphones and external studio monitors, or share a movie soundtrack across two different Bluetooth headsets with a friend, standard System Settings will not let you select more than one output destination.

Fortunately, macOS includes a powerful built-in utility called Audio MIDI Setup. Tucked away in your Utilities folder, this tool allows you to create a virtual Multi-Output Device. A Multi-Output Device bundles multiple physical audio outputs into a single unified virtual endpoint, mirroring your Mac’s audio stream across every selected speaker or headphone jack in real time. This tutorial walks you through opening Audio MIDI Setup, creating a Multi-Output Device, resolving drift and latency sync issues, and setting it as your default sound output.

What is a Multi-Output Device vs. an Aggregate Device?

Inside Audio MIDI Setup, Apple provides two virtual routing constructs that serve opposite functions:

• Multi-Output Device: Takes a single audio stream and splits/mirrors it simultaneously across multiple output interfaces (such as built-in speakers + USB headphones). It handles sound output only.
• Aggregate Device: Combines multiple independent audio input/output channels to increase total track count (for example, combining two separate USB audio interfaces to record eight distinct microphone channels in Logic Pro or GarageBand).

Creating a Multi-Output Device in Audio MIDI Setup

To configure your multi-speaker virtual audio endpoint on macOS:

1. Open Finder, navigate to Applications > Utilities, and double-click Audio MIDI Setup (or press Cmd + Space and type “Audio MIDI Setup”).
2. In the Audio Devices window, click the Add (+) button located in the bottom-left corner of the sidebar.
3. Select Create Multi-Output Device from the pop-up menu.
4. A new entry titled Multi-Output Device appears in the sidebar. Double-click its name if you wish to rename it (for example, Headphones + Desktop Speakers).
5. In the right-hand configuration pane, review the list of available audio devices under the Use column.
6. Check the checkbox next to every output device you want to stream audio through simultaneously (such as External Headphones, MacBook Pro Speakers, or your connected Bluetooth earbuds).

Configuring Master Device and Drift Correction

Because different audio interfaces use separate internal clock generators, playing audio across multiple hardware chips can eventually cause timing drift, echo, or subtle audio artefacts. Audio MIDI Setup solves this using Drift Correction:

1. Identify your primary audio device (such as your high-fidelity USB DAC or wired headphones) and select it in the Master Device dropdown menu at the top. The master device sets the clock timing for the entire group.
2. Locate the Drift Correction column in the device list.
3. Check the Drift Correction box for all secondary devices (every device except the Master Device). macOS dynamically resamples secondary audio buffers to keep all outputs tightly synchronised in real time.

Setting the Multi-Output Device as Default Audio Output

Once created, instruct macOS to route system sound through your new virtual endpoint:

1. Inside Audio MIDI Setup, right-click (or Control-click) your new Multi-Output Device in the left sidebar.
2. Select Use This Device For Sound Output.
3. Alternatively, click the Sound icon in the macOS menu bar or Control Centre, and select your Multi-Output Device under the Output section.
4. Play any media file, YouTube video, or music track. The audio will broadcast across all configured outputs concurrently.

Managing Volume Controls and Troubleshooting

When using a Multi-Output Device, you may notice that the macOS keyboard volume keys (F11 and F12) or the menu bar volume slider become greyed out. This is expected behaviour:

• Why System Volume Disables: Because different connected speakers have varying output impedances, sensitivities, and amplifier gains, macOS disables master digital attenuation to prevent blasting one device while underpowering another.
• Adjusting Volume: Adjust physical volume knobs directly on external speakers or headphones, or use in-app volume sliders within Spotify, Music, or web browsers.
• Bluetooth Latency Mismatches: If pairing wired speakers with Bluetooth headphones, Bluetooth’s inherent wireless encoding latency (typically 100–200ms) will create an audible echo. For best results, pair devices with identical physical connection types (such as two wired outputs or two Bluetooth devices with similar codecs).