How to Create an Aggregate Device in macOS Audio MIDI Setup

What an aggregate device does

An aggregate device is a virtual audio input and output that combines two or more physical audio devices so macOS and your apps see them as one device. This is useful when an app can only select one microphone or interface at a time, or when you want to record from multiple USB microphones together. The aggregate device itself does not change the behavior of the connected hardware; it only groups the available input and output channels under a single selectable name.

When use of an aggregate device is appropriate

Use an aggregate device when you need more than one audio device to appear as a single device in an app, such as a recording or conferencing application that offers only one microphone source. This guide covers setup and configuration of an aggregate device. If a device is not detected, protected by the system, or already misbehaving, that is a separate diagnostic situation and is not addressed here.

Before you begin

• Connect the physical audio devices, such as USB microphones or audio interfaces, before opening Audio MIDI Setup.
• Use the same clock source concerns as for any multi-device audio setup. macOS Audio MIDI Setup includes a drift-correction option, but the available options and their behavior depend on the connected hardware and macOS version.
• Make sure each device appears as a recognized audio device in macOS before grouping. Detection issues should be resolved before attempting to create an aggregate device.

How to create an aggregate device

• Open Audio MIDI Setup.
• Select the Audio Devices window if it does not appear by default. This is the window showing the active audio input and output devices available to the Mac.
• Click the add button near the bottom-left area of the Audio Devices window.
• Choose Create Aggregate Device from the menu.
• A new aggregate device appears in the device list. Select it.
• In the settings area, enable Use for each physical device that should belong to the aggregate. Do not enable devices that should remain separate.
• If desired, enable drift correction or change the clock source from the aggregate-device settings provided by Audio MIDI Setup. Only change this if required for your configuration.
• After configuring the aggregate, select it as the input or output device in the app you want to use.

How to check that the setup worked

In the app where you want to use the devices, choose the newly named aggregate device as the microphone input. Speak or play audio into each connected device and verify that the app shows the expected channel activity. The observable completion check is that the app accepts the aggregate device as its selected input or output and receives signal from the grouped hardware.

Important boundaries

An aggregate device affects audio device selection and channel grouping. It does not grant microphone access to apps. App-level microphone permission is controlled separately through the Mac's privacy settings, and an aggregate device may not be selectable in an app if that app lacks the required microphone access.

Also, this setup applies only to audio devices in macOS Audio MIDI Setup. Webcam video capture is a separate system and is not managed through an aggregate audio device.