Guides / Virtual audio drivers and Audio MIDI Setup

How to create a Multi-Output Device on a Mac (and keep hearing your audio)

Tested on macOS 26.4.1 (Tahoe), Apple M3 Max, 3 Sept 2026. Updated 2026-09-03.

A Multi-Output Device is an Audio MIDI Setup device that sends the same playback to two or more outputs at once, typically your speakers and a virtual driver such as BlackHole. You build it with the Add button, Create Multi-Output Device, tick the speakers first and BlackHole second, enable Drift Correction on BlackHole, then choose it as the sound output. The price is that the volume keys stop working.

Why do my speakers go silent when I select BlackHole as the output?

Because BlackHole is not a speaker. It is a virtual audio driver: a device with an output side and an input side wired together inside Core Audio. Anything the Mac sends to BlackHole's output appears at BlackHole's input, where a recorder can read it. Nothing is connected to a loudspeaker. So the moment you choose "BlackHole 2ch" in System Settings > Sound > Output, every app's sound flows into the driver and nowhere else. YouTube keeps playing, the level meter in Audacity moves, and the room is silent.

This is the single most common surprise with any loopback driver and it is not a bug. macOS has one default output device, and a driver can only be that device by replacing your speakers. The fix is not a setting inside BlackHole; it is a second, composite device that feeds both. That is what a Multi-Output Device is for: Apple's guide says that when you add two devices to a multi-output device, audio sent to the primary device also plays through any other device in the stack.

The trap does not exist with ScreenCaptureKit, which taps the stream on its way to the output you already use; see what a virtual audio driver is.

How do you create a Multi-Output Device on a Mac?

Apple's steps plus the ordering rule from the BlackHole wiki, checked on macOS 26.4.1:

1. Open Audio MIDI Setup (Command-Space, type Audio MIDI). Choose Window > Show Audio Devices if needed.
2. Click the Add (plus) button at the bottom of the sidebar and choose Create Multi-Output Device.
3. On the right, tick the Use box for your real output first (MacBook Pro Speakers, or your interface), then tick BlackHole 2ch. The BlackHole wiki states that the built-in output or another 2-channel device must be listed as the top device; if BlackHole ended up first, untick and retick the boxes to change the order.
4. Open the Primary Device pop-up and choose your speakers or interface. Apple's guide: "click the Primary Device pop-up menu, then choose an output device."
5. Tick Drift Correction for BlackHole (every device except the primary).
6. Control-click the new Multi-Output Device in the sidebar and choose Use This Device for Sound Output. It now also appears in System Settings > Sound > Output.
7. In your recorder (QuickTime, Audacity, OBS, a DAW), choose BlackHole 2ch as the input.

To undo everything, select the Multi-Output Device and click the Remove (minus) button, then choose your speakers again in System Settings > Sound. If you also record your own voice you need an aggregate device for the input side; the Multi-Output only solves hearing.

Why can't I change the volume when a Multi-Output Device is selected?

Because macOS does not expose a volume control for composite devices. With the Multi-Output Device selected, the keyboard volume keys show a crossed-out speaker and the Sound slider in System Settings is grayed out. The BlackHole wiki says it plainly: "Unfortunately macOS does not support changing the volume of a Multi-Output device but you can set the volume of individual devices in Audio MIDI Setup."

Practical workarounds, in order of convenience:

• Set the volume before switching to the Multi-Output Device. Select your speakers in System Settings > Sound, set the level, then switch.
• In Audio MIDI Setup, select MacBook Pro Speakers (not the Multi-Output Device) and drag the Output volume slider. This changes what you hear without changing what BlackHole receives, which is useful because it keeps the recording level at unity.
• Use the volume control inside the app that is playing (YouTube, Spotify, Zoom). This does change the recorded level, because the app lowers the signal before it reaches the driver.

This limitation is one of the concrete reasons a driverless recorder can be simpler: with ScreenCaptureKit the speakers remain the default output, so the volume keys keep working and the capture is unaffected by them.

Why does the Multi-Output Device crackle or fall out of sync after a while?

Two devices, two clocks. Your speakers run on the Mac's audio clock; BlackHole runs on a virtual clock. Without correction, one drifts relative to the other and the audio going to BlackHole starts to glitch after minutes to hours. The BlackHole README's answer for multi-output glitching after some time is: enable drift correction for all devices except the Clock Source, also called Master Device or Primary Device.

Checklist when a Multi-Output Device misbehaves:

1. Primary Device is the real 2-channel output, listed first. BlackHole first is the documented cause of no sound at all.
2. Drift Correction is ticked on BlackHole and unticked on the primary.
3. Both members share the same sample rate. Select each in the sidebar and check the Format pop-up. 48 kHz on both is the safe choice, and it matches what system audio runs at on the author's Mac.
4. No other app has grabbed BlackHole exclusively. A DAW set to BlackHole as its output while you record from BlackHole creates a feedback loop.

If the problems persist, the BlackHole troubleshooting page covers the driver side, including the coreaudiod restart.

Do you need a Multi-Output Device at all?

Only if you use a loopback driver. The Multi-Output Device exists to patch over the speaker-silence problem that BlackHole and Soundflower create. If you route audio between apps (DAW into OBS, a browser into Ableton) you have chosen a driver for a good reason, and the Multi-Output is part of the price.

If your only goal is a recording of what the Mac plays, there is no driver, no composite device and no volume problem: since macOS 13 Apple's ScreenCaptureKit captures system audio directly, and recorders built on it (AirCheck among them) leave your output device untouched. That path is described in recording Mac audio without BlackHole. OBS on macOS 13 and later uses the same mechanism for its macOS audio capture source, though it writes a video container rather than an audio file.

Unfortunately macOS does not support changing the volume of a Multi-Output device but you can set the volume of individual devices in Audio MIDI Setup.

Existential Audio, BlackHole wiki (Multi-Output Device)

Hearing your Mac while capturing its audio: the options compared (3 Sept 2026)

Step counts are the numbered steps on this page and on Apple's guide. Loopback price from rogueamoeba.com on 3 Sept 2026.

Where AirCheck fits

AirCheck ($39, macOS 14 or newer) records system audio through ScreenCaptureKit, so the Multi-Output Device is unnecessary: your speakers or interface stay the default output, the volume keys keep working, and the capture arrives at the device rate (48 kHz, 24-bit on the author's Mac) regardless of the listening level. One Screen Recording permission replaces the seven steps above. AirCheck's own playback is excluded from the capture, so reviewing a take does not record itself.

When you do not need it: If you need BlackHole for routing (DAW to OBS, browser into Ableton), keep the Multi-Output Device; it is free and AirCheck does not route audio between apps.

Questions people ask

How do I hear audio while recording with BlackHole on a Mac?

Create a Multi-Output Device in Audio MIDI Setup containing your speakers (first, as Primary Device) and BlackHole 2ch, enable Drift Correction on BlackHole, and select the Multi-Output Device as the sound output. Record from BlackHole 2ch as the input.

Why is my Multi-Output Device silent?

The BlackHole wiki documents one cause: BlackHole is listed as the top or primary device. Untick and retick the Use boxes so the built-in output or your interface is first, then set it as Primary Device.

Can I adjust volume on a Multi-Output Device?

Not with the keyboard or the Sound settings slider; macOS disables them for composite devices. Select the individual speaker device in Audio MIDI Setup and move its output slider, or adjust the playing app's own volume.

Is a Multi-Output Device the same as an aggregate device?

No. A Multi-Output Device duplicates playback to several outputs. An aggregate device combines several inputs (and outputs) into one device so an app can read them together. Recording mic plus BlackHole needs the aggregate; hearing while routing needs the Multi-Output.

Sources

• Apple: Play audio through multiple devices at once in Audio MIDI Setup
• Existential Audio: BlackHole wiki, Multi-Output Device
• Existential Audio: BlackHole README (FAQ on drift correction and primary device)
• Rogue Amoeba: Loopback purchase page

Related guides

• How to create an aggregate device on a Mac
• Is BlackHole safe for a Mac?
• BlackHole not showing up in Audio MIDI Setup: how to fix it
• What is a virtual audio driver, and when do you need one on a Mac?
• What is Audio MIDI Setup on a Mac?
• Is Soundflower safe, and does it still work on a Mac?
• Virtual audio drivers and Audio MIDI Setup: all guides
• Every guide, by topic