Edifier has gotten some good reviews on their active speakers. As the OP noted, seems it's the Monoprice sub with issues.
I have looked at this closer.
That Monoprice is a miserable piece of you know what. It quotes and FR down to 25 Hz, but 25 Hz is the 10 db down point. So that actually means the sub has a falling response around 50 Hz. So it is NOT a sub at all. I suspect there is a lot of ripple and the miserable thing is just designed to give out some sort of ponk or honk at around 80 Hz.
Now the Edifer active speaker does not have a variable crossover. They quote a response down to 60 Hz, which for a ported 4" speaker could well be the 3 db point.
Since there is not high pass on the Edifer I suspect the cross out to the sub is around 60 Hz, so that would make that Monoprice sub virtually silent and useless.
Yes, people do need to be far more circumspect purchasing this sort of gear.
Edifer by the way do quote a not very spectacular S/N of 85 db, so that tells me they are really shopping at the bottom end of the market for there OP amps and IC power amps. From the specs, I can guarantee the power amps are the cheapest of the cheapest of IC horrors. Not likely to be known for longevity of you turn them up much.