It can be done passively as well. Had Kappa8's that had a switch on the back to high pass the lowest octave to be an easier load to the amp. Dependant on the amp's capabilities. It made no difference to my amp at the time.
It can also protect the speakers from DC with direct coupled electronics, which could cause damage or reduced headroom.
It can also protect the speakers from DC with direct coupled electronics, which could cause damage or reduced headroom.