I’ve got two sets of monitors for a/b purposes... one decent set and One crappy set. Commercially mastered tracks sound good on both. . my tracks sound good in the decent set but overdrive the crappy set. any thoughts on this?

Hello Everyone,
I'm brand new to the forum so be gentle. I hope I'm in the correct area to asked this question.
I have a powered monitor and it powers up, and sound comes out, but the volume is very low and it is distorted. How can I determine if the problem is the speaker or the amp?
If it's the amp, what would be the most logical problem.

I have just bought an Alesis SR-16 and when I tap the pads or play the demo, the sound is extremely low and so distorted that I can hardly identify the different voices.