Originally Posted by gumplunger
Impulse responses are linear, meaning they don't take into account the dynamics of the input signal, so it doesn't really matter what your input level is as long as its not super low.
Actually they are not. If you have an analyzer program which shows a waterfall representation of an IR (and maybe it's only the good ones) you can see how the EQ curve changes as a function of time. What variables affect how well this transfers to an actual difference in sound, I don't know.