Is Edifier c3 broken or is it right?

Question

Electronics

I got 2.1 speakers with Edifier C3 subwoofer, not new ones. I began to notice that, like, when a quiet sound, then he himself becomes even quieter, and then louder. some kind of swing is obtained, it seems that in one column it stops playing loudly, and in the second it remains. unclear. maybe this is their auto volume control or what is it?