Group Delay Correction?

Can anyone point me to info or a schematic for group delay correction? I don't have a bad problem with my sub, but, hey, it's a hobby, and I want to play with my sub! I'm playing with a RSS315HF-4 and a Bash 300 amp (nice for modifications!), in a vented box. Maybe I should use something like low and high pass filters and digital delays, and then remix them?