Dirac does let you specify limits for the correction window. If you wanted it to leave >500hz alone, that's easy.
I just found that I like the sound better for Dirac to do its thing >500hz. If you try to push drivers beyond their limits for extra extension at the top or bottom end, I found that does more harm than good, so it is good to set limits on the correction window.
Within the limits of the speaker, though, Dirac seems to do a good job at avoiding over-correction. They say they only correct problems that are consistent from the 9 measurement locations.