ATC SCM40As sound quality at low voume

I recently became very intrigued by the concept of powered speakers with active crossovers, particularly the ATC SCM40A. I read all the reviews I could find and more than one of them mentioned that while they sounded great at loud volume levels, they sounded poor at low volumes. I was surprised. I'm not used to hearing that. I'm not really sure what could explain this. In the grand scheme of things, I'd much rather have a speaker that played loud without strain, but I do often listen to music during "quiet hours" when I shouldn't disturb others in the house. Has anyone experienced the ATCs at lower volumes? Does anyone have an explanation?