Identify every audible endpoint
List the group members in Audio MIDI Setup and locate the actual speakers or headphones. A display’s built-in speakers may be audible alongside a separate sound system. Keep the viewing position in the note because the listening result depends on the physical arrangement.
For an illustrative setup, television speakers and nearby external speakers can both reproduce dialogue. Turning down one path temporarily can help establish whether two audible copies are involved. Do this at a comfortable level; do not compensate for an unclear mix by making every endpoint louder.
Return to one simple baseline
Choose the original single output and play the same short dialogue passage. Then compare the intended output group without changing the media file or app. Apple documents choosing included devices and a primary device, but the existence of those controls is not a promise of a calibrated multiroom system.
Record whether the complaint disappears with one output. If it remains, do not keep attributing it to the group solely because the group was recently created. The programme mix, room acoustics and other output processing may still need separate investigation.
Choose the useful arrangement
If two simultaneous speakers are not required, use the single path that meets the viewing need. A more complex configuration is not automatically a better listening setup. If multiple endpoints are necessary, consult the relevant device documentation for a suitable supported arrangement.
When seeking help, provide the Mac version, group members, primary device, physical connections and single-versus-group comparison. Keep private file paths out of logs. Avoid claiming that the streaming service introduced an echo when the observed difference follows a local output configuration that has not yet been isolated.