Logic Pro (X) Logic Pro X Can't set up an aggregate device


New Member
I'm using Logic Pro X 10.6.3 on an iMAC OS Catalina10.15.7 I can't set up an aggregate audio device.
I have followed directions from the Apple website and I looked at a Youtube video on how to do this but....
My iMac doesn't show any selection for an aggregate device when I launch Audio/Midi set up.
The set up only shows midi inputs from my two devices: Clarett 4 pre USB and a Behringer UMC 204HD.
These devices do work separately if I use them one at a time when I'm using Logic.
My Audio/Midi set up window doesn't look anything like the Youtube video or the screen shot on the Apple website.
Any help is appreciated.

Peter Ostry

Staff member
... selection for an aggregate device ...
The set up only shows midi inputs from my two devices

An Aggregate Device is a virtual audio device and has nothing to do with MIDI.
If you see MIDI devices in Audio MIDI Setup, you are looking at the wrong window.
  1. Open Audio MIDI Setup
  2. Close all windows that are open there.
  3. In the main menu select "Window -> Show Audio Devices".
  4. The "Audio Devices" window pops up and you see a list of your audio devices on the left.
  5. At the bottom left corner click on the tiny plus sign and select "Create Aggregate Device".
  6. Now you see a new entry in the list called "Aggregate Device". In the right part your audio devices are listed again.
  7. Decide which device you want to have as master. Normally you take the one you think has a better synchronization. In your case I would take the Focusrite as master.
  8. Double click on "Aggregate Device" and change the name. For example to "Clarett+UMC". The name should also give you information about the order of the devices later.
  9. In the right list you see your devices with checkboxes in front of them. First of all activate the checkbox of the Focusrite. This will become the master.
  10. Afterwards activate the checkbox of the Behringer.
  11. Now you have the Focusrite in the first line and the Behringer in the second. The numbers are the number of input and output channels. The Behringer should automatically have the "Drift Correction" checkbox checked at the end of the line. That's fine.
  12. In the upper right part you see a graphical representation of the arrangement of your devices and the input and output channels. This is how you have to set them up in Logic.
The Aggregate Device is ready and from now on you can select it as input and output in any program.

While you use your Aggregate Device, you can't see in the audio applications where the Clarett is and where the Behringer is. You need to know the order and how many channels each device has. If you don't like the order of the devices, you have to change it in the Audio MIDI Setup. The best is to deactivate both and click the new master first and then the other one. Don't forget to change the name of the Aggregate Device, otherwise you won't know your way around later. You can also configure multiple aggregate devices.

Below is a screenshot as example. I have only one audio interface, so I made an Aggregate Device with my Metric Halo interface and the Mac’s internal speakers:


(This screenshot is from a Mac mini M1 running Ventura, your screen may look slightly different.)

This screen tells me that the Metric Halo is the first one and the master, and is configured for 32 input and output channels. The Mac has only 2 output channels and they are after the Metric Halo. If I want my Logic playback through the Mac’s speakers, I have to select channels 33+34 as outputs.

Your devices have both inputs and outputs and the numbering system applies to inputs and outputs. If you forget the channel numbers and can’t find the channels in Logic, just look at the Audio MIDI Setup, the numbers are always there.
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New Member
Peter, Thank you so much for helping me. I was able to set up an aggregate device after reading your directions.
I don't know why I didn't think of checking the "WIndow" options in the menu bar.
Thanks again.
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