Reflective frequency ballpark for FRK and other higher density materials?

So Im pretty sure I've dunked my head about as far as is useful into the tub for the whole studio treatment thing, but one thing is sort of irking me. The general consensus is that you don't want a totally broadband absorber in a corner, right? Looking at what needs to be tackled in my room, Id like to not absorb above a certain point anyway, so I've been searching high and low for any kind of numbers regarding what above what frequency FRK or other less porous materials reflect.



I've seen generalisations like MF and HF bandied about, but since I've seen people say that LF is anywhere from 20 to 300hz, and others will argue that 60hz and below is sub-bass, 60 to 100 is bass and 100 to whatever is low mids, it makes it a little difficult to pin down where that might be.



Is there any kind of data regarding where it is that FRK or other denser types of material starts to reflect, or is that sort of data conditional to the room and source setup?



Im about to start assembling traps and I'd like to know beforehand so I can maybe even add some denser covering if it would help reflect more mid to high frequency response.



Ballpark numbers (as opposed to terms like HF or LF) would be most appreciated.



Thanks!

Reflective frequency ballpark for FRK and other higher density materials?