A linkwitz transform is a way to electrically alter the final system Q and frequency response. It is an EQ of sorts... a specialized EQ designed specifically to counter the rolloff curve of a driver in a sealed enclosure.
I
think a BFD (if it could cover low enough freuqencies, which it can't) type of EQ with appropriate filters could approximate a LT decently.
Read more about it
here,
here, and
here.