Rythmik's response window is pretty much nonsense. Any sub can maintain that kind of response at a low SPL. Raise the levels a bit and compression will certainly change that response. There is a big difference between the Monolith subs and the Rythmik subs; when you raise the levels on the Monolith subs, the response hardly changes, all the way out to the highest drive level. That is mandated by THX which is very strict on compression behavior. For THX certification, the response shape must hold at all drive levels.