I notice that after listening on battery power, sometimes one channel seems less loud or cuts out?
The foxL has overload protection that kicks in much quicker on battery than it will on AC (foxL’s power is double when plugged into the wall), you’re probably playing notes/level that cause clipping, and the protection circuit is activating to keep from damaging the speakers. The foxL is pretty amazing for its size, but it is small which creates some compromises. If you play the same things using AC, you will have more volume and much less chance of the protection circuits kicking in.
