funky sub sound when power is turned up

[playmysong 2]

I've heard a few subs make a funky sound when more power is applied to them that just doesn't sound like the bass the artist put in the song. On low volumes its fine. On higher volumes It sounds like the sub is puking. I hate that sound and i turn the bass down to when its gone. I've heard it mostly on punchy bass, long drawn out bass is usually fine. What causes this, is it when a sub exceeds its xmax or is that overrated in knowing what the sub sounds like as well? That's my only guess. I haven't heard lots of different subs but all the ones i heard did it.