A lot of the earlier Stax have issues with channel imbalance. Check for dust buildup, these headphones are very sensitive to dust, being electroSTATIC, but remember to be careful cleaning them, these membranes are only a matter of single-digit microns thick. Also, replace the ear pads, a slight channel imbalance might have to do with the fact that the SR-X is pretty picky about spacing. Verify as well that it's not anything else in your amplification chain. They are super picky, even make sure that if you have an SRD-7 as the energizer box, that the speaker terminal hookup wires haven't been nicked or don't have proper contact. Chances are, though, with a cheaply found pair, that there's moisture damage.