Define why aggregation is needed
List the input and output interfaces the application actually needs. Apple’s Audio Devices documentation distinguishes aggregate and multi-output choices. If the goal is ordinary television sound through one speaker system, start with that simpler output rather than creating a combined device without a requirement.
A hypothetical production task might need one interface’s inputs with another interface’s outputs. A casual viewing task may not. Keep the application requirement and physical device names in writing so the chosen configuration has a clear purpose beyond adding more options to a menu.
Follow the supported combination steps
Apple documents creating an Aggregate Device in Audio MIDI Setup and selecting the relevant components. Check the current guide for the installed macOS version. Its instructions say the devices should use the same sample rate, so inspect that property on each included component.
Preserve the original individual-device settings before changing them. Use a short permitted audio sample to confirm the intended application can use the selected aggregate. A combined entry appearing in a list is not proof that each cable, driver and channel assignment functions as expected.
Keep a simple recovery route
Retain the original single-device selection while evaluating the aggregate. If sound disappears, return to that baseline and record whether the problem follows the new group or also occurs individually. Avoid changing programme passwords or media files to investigate a newly created hardware configuration.
When seeking help, provide macOS version, interfaces, selected sample rates, intended application and the failing channel or direction. Keep serial numbers and private project audio out of public logs. A successful aggregate configuration serves its defined application task; it is not a guarantee of synchronised room speakers or a universal improvement in video playback.