Stereo channels
Also called left and right channels · balance
Stereo audio has two channels, left and right, each sent to its own speaker or earcup. Sound from only one side usually means a balance setting, a mono setting or a loose connector.
In practice
Most music, films and games are mixed in stereo, so a missing channel loses part of the sound rather than just making it quieter. Footsteps in games, instruments in music and dialogue placement can all disappear. The cause is more often a balance or mono setting, a half inserted plug or a damaged cable than broken speakers.
How to check
Play the left and right tones in the speaker test and confirm each comes from the right side. If one side is silent, check the balance setting, the mono audio accessibility setting and the plug. Wiggle the cable near the plug while the tone plays. Sound that cuts in and out with movement points at the cable.