Hi Chris.
Even if the two speaker units look the same they are not. The top one is mid range and the bottom one is bass. When that is said I would say that it sounds like your top unit is malfunctioning.
Whether it is due to a broken unit or a faulty crossover I can't say.
The should be equally loud (top and bottom)
Regards
Razz
Beocenter 1, Beosound 1 and high hopes for more to come.