Audio Volume Control for Multi-Device Output on MacOS

Manage volume for Multi-output Audio devices on macOS without Soundflower

This article explains how to enable native-feeling volume adjustment with Multi-Output Devices without having to use Soundflower.

I use this method to play sound on both my iMac and connected LED Cinema Display.

WHY?

When playing sound on multiple output devices simultaneously on MacOS you lose the ability the adjust volume when using the built-in MacOS utilities.

One way around this is to use Soundflower, it is an additional audio device/driver through which all the audio is routed. When using Soundflower as the output devices for Multi-Output Devices, volume control is restored.

The downsides are a complicated setup, it is error-prone where I’ve had multiple instances of playing white noise on all speakers at full volume, and the additional audio-routing takes up some CPU cycles and increases processor load.

HOW THEN?

1. Create a Multi-Output Device with all desired output devices.
2. Install an open-source Application to enable control of the aggregate device with native on-screen display and keyboard shortcuts.

First, launch “Audio MIDI Setup.app” from /Applications/Utilitiesfrom the Finder.

Then, create a new Multi-Output Device and check all the desired output devices to play audio to.

Enable the new device by right-clicking and selecting “Use This Device For Sound Output”

Next, simply install MultiSoundChanger from Github — the app is open-source so you can build it yourself using Apple XCode or download a binary release here — the latest release of this fork is “0.2” and not “1.0”. Download or build the binary and move it to /Applcations in the Finder.

The application lives in the Menu Bar with the status menus on the right side. It allows to change the left-right balance when using two devices, volume and selecting an output device.

On first start, the app will ask for “Accessibility” permissions to enable it to access the volume up/down/mute media keys on the keyboard. If you “Allow”, it will bring up System Preferences, then you unlock the little bottom left padlock and check “MultiSoundChanger.app”. If you don’t want to use the keyboard you can skip this step and click “deny” instead.

That’s it, except the app won’t start automatically when your machine boots. To enable autostart open “System Preferences”, then “Users & Groups”, click the “Login Items” tab and then the small “+” button and select the “MultiSoundChanger.app” from the dialog.