Start with the easiest failure points
Loose plugs, partially seated adapters, and damaged inline remotes cause more one-sided audio than people expect. Before assuming hardware failure, reseat every connection and rotate the plug gently to see whether the missing side cuts in and out.
Separate source issues from headphone issues
Use the channel test on a second device. If the problem follows the headphones, inspect the cable, hinge, ear cup entry point, and detachable connectors. If the problem disappears, the source or adapter is the more likely culprit.
Wireless models add software variables
Bluetooth sets can show one-sided playback after a bad firmware update, partial pairing reset, or balance setting change in the operating system. Check accessibility and sound settings before you open the hardware.
A missing channel is often mechanical, not mysterious. Cables, connectors, and software balance settings fail more often than matched drivers.
When repair makes sense
Replaceable cables are worth testing first because they are the cheapest fix. If the issue remains inside a sealed wireless ear cup, repair value depends on the model and warranty. For inexpensive consumer sets, replacement is often more practical.