Choose repetition or additional discrete channels
Apple’s Multi-Output guide says audio sent to the primary device also plays through the other devices in the stack. Its Aggregate guide instead gives an example of an eight-channel and two-channel device becoming a ten-channel device. Those descriptions identify different routing goals.
For two outputs receiving the same programme, begin with the documented Multi-Output task. For an application that needs separately addressable channels across interfaces, examine Aggregate Device support and channel mapping. Do not assume that selecting one combined name gives every app the same arrangement.
Create only the device appropriate to the task
In Audio MIDI Setup’s Audio Devices window, use Add to create a Multi-Output Device. Select the participating devices with their Use checkboxes, then choose the Primary Device from the offered menu. Give the result a recognisable name so it is not confused with an individual display or headset.
Select the intended combined output in the actual playback route and use a short reference passage. Confirm each physical output separately. A virtual device appearing in the sidebar does not prove the player selected it, and an unplugged participant should not be treated as a working speaker merely because its name remains saved.
Keep aggregate synchronisation instructions in their proper scope
Apple’s Aggregate Device documentation discusses matching sample rates, choosing a clock or sync source and using drift correction or resampling when devices are not hardware-synchronised. This addresses timing between device clocks. It does not establish that every combined route has zero fixed output latency or that the same checkbox layout exists in Multi-Output settings.
If a comparison involves an aggregate, use the controls documented for the installed version and record the participating interfaces. If the issue is a constant echo between speakers, retain that observation separately from gradual timing drift. Do not copy a setting label from another virtual-device type as a universal solution.
Preserve a simple return route
Record the previous ordinary output and return to it after the comparison if desired. Apple documents removing a created combined device, but deletion is not required merely to stop using it. Keep the original physical device identities intact.
No Mac or audio hardware was tested here. The procedure distinguishes documented routing concepts and proposes a controlled check, without certifying a specific app’s multichannel behaviour or a particular pair of headphones.
Sources and scope
Scope notes distinguish published documentation, supplied information and editorial methods. They do not report a hands-on service test.
- Apple: MultiOutput routing — Officialcurrentindexed27guide:CreateMultiOutput/Use/PrimaryDevice and repeatedoutput; no unverifiedper-devicevolumecontrols.
- Apple: AggregateDevices — Officialindexeddiscretechannelcombination and samplerate/clockscope.
- Apple: aggregatesynchronisation — OfficialcurrentindexedSync/clock/resampling discussion; notcopiedasMultiOutputcheckboxlayout orconstantdelayguarantee.
