It corrects the full frequency range, but doesn't specifically recognise your subs. You need to set the crossovers yourself etc. But once you have ran the software you can create custom curves in an instant etc. If you are a whiz with REW you may be able to get the same results for free, but I am not quite at the level of expertise, so have went the Dirac route.
I must admit, I have not successfully implemented it yet, having difficulty with background noise etc.
I have the day off work tomorrow and plan to have another crack at it