FFT-based field measurement systems have made it possible for us to do phase alignment at fixed installations as well as at live events, where every venue demands a different approach. This is particularly important since mid-high boxes are often flown and subwoofers remain on the ground, meaning that phase differences at the listener location can be very significant.
An interesting article on ProSoundWeb going over the concept of phase, detailing the measurement process and the remarkable improvement it can bring to a system.
The full article can be found here: http://www.prosoundweb.com/article/phase_alignment_between_subwoofers_and_mid-high_cabinets/