Why is one of my speakers louder than the other while using the N22 at lower volumes?

This is actually normal behavior. It's is a tradeoff of using an analog potentiometer for the N22. Analog potentiometers are tactile, and don't require a microprocessor like a digital encoder would, but they sometimes do have some volume imbalance at lower levels.  An easy solution for this is to raise the volume of your N22, and lower the volume at your source device.