How To Use Multiple Audio Inputs And Outputs In Mac OS X

Mac: OS X has a neat feature you might not know about: it can create an aggregate set of audio devices so you can use multiple inputs and outputs in any application, allowing you to configure custom surround sound setups, record from more than one audio interface at a time and more.

If you've been working with audio in Mac OS X for a while, you may remember that you could only use one CoreAudio input/output device at a time. That meant your internal sound card, an external USB audio interface or the microphone on your webcam — but not all of them. That changed recently, although I'm not sure how far back. If you haven't explored aggregate audio settings, you should check it out to see if there's anything it can do for you.

Setting up your own aggregate audio device is really simple. Just follow these steps:

  • Open up Audio MIDI Setup (in Your Hard Drive -> Applications -> Utilities).
  • Click the + button in the bottom left-hand corner and choose "Create Aggregate Device."
  • Double click on the name "Aggregate Device" to rename it (if you want to).
  • In the panel on the right side-side, choose any input and output devices you want to be able to access through this aggregate device. Once you've made your selections, you're done!

So what can you do with your aggregate device? If you have multiple audio outputs, you can use multiple sets of speakers to either pump audio into a different room or create a surround-sound setup. If you want to record from microphones and a Skype call for a podcast, you can download Soundflower to record computer audio and create an aggregate device with it and the audio interface responsible for your microphone(s). If you want to record multiple microphones but can only hook up a maximum of two (for example) to each audio interface, just aggregate your audio interfaces and record from all your microphones at once.

If you're working with audio on a Mac, there are a lot of ways this can be useful. These are just a few examples. I hadn't bothered with this feature until I was looking for an easier way to integrate audio from Skype guests into our podcasts. Learning how it worked helped me solve that problem easily. It's just one of those hidden features worth knowing about.


    If you're in Snow Leopard or earlier, "create multi-output device" will not be available, and thus you won't be able to use this technique to stream music through e.g. multiple pairs of headphones (without using a y-splitter at least). To do that, you want to use a combination of two apps: MTCoreAudio AudioMonitor, and SoundFlower (just google both of them). You'll need to run multiple instances of AudioMonitor: to do this, go into the package Contents/MacOS and run the "AudioMonitor" command in terminal.

      and that command is? sorry to bother you but im trying to do exactly this on snow leopard for my daughters party tomorrow night.

    This is excellent - it lets me play sound from my Mac to AirPlay speakers (Apple TV or AirPort Express).

    Now suppose I have multiple sets of AirPlay speakers (both Apple TV and AirPort Express). How can I play to all of them simultaneously?

    I think this is what I'm looking for! I have an audio interface and i want to listen the monitor sound from logic in the interface monitor out and in the mac out at the same time. I'll try when i get home!

    I've tried to add two USB mics using this method for Skype calls but can only get a signal from one mic. Detailed here: What am I doing wrong?

    First of I am using a Mac Pro (2013) with macOS Sierra 10.12.1 Beta (1682548a) with a OWC Thunderbolt 2 (Dock). The Mac Pro have (2) 3.5mm audio plugs - left output - right input - have same audio connections on OWC's Dock. Problem is no matter what microphone I use, unable to get sound in Mac Pro through different mic's. I tried to install Soundflower v1.6.6b but 'The Installation failed'.
    Now that Sierra has Siri I need to input sound. Is there an alternative to Soundflower. Or what do you suggest. No problem in copying/listening system sound to an application.

    This did not work for me.

    1. IMHO, there's a very important step missing, which is to right-click on the new device created and select "Use this device for sound output"
    2. Instead of aggregate device, I created "Multi-Output" device and then did point one viz. to "use this device for sound output".

Join the discussion!

Trending Stories Right Now