You can also rule out your ears by simply turning around. I think it's room acoustics and speaker placement that are causing your problem. Same issue in my room, left speaker is further from the corner than the right, more rear reflection and sound is louder on that side. When I change the placement of the right speaker, the problem resolves.
I once had an amp that used a timed relay to protect the speakers from any turn on/turn off pulse. After a few years the relay's contacts degraded and affected the sound in a very similar manner. Sometimes the right channel wouldn't even play until the volume passed a threshold level, and at low volumes the left channel was always louder.
I once had an amp that used a timed relay to protect the speakers from any turn on/turn off pulse. After a few years the relay's contacts degraded and affected the sound in a very similar manner. Sometimes the right channel wouldn't even play until the volume passed a threshold level, and at low volumes the left channel was always louder.