Stuff the area behind the woofer tightly, and progressively looser towards the vent. The object being to convert acoustic energy to thermal and reduce peaks/nulls in the cabinet response. In other words: Add 1/2lb/ft3 of fiberfil to the coupling volume(area directly behind the woofer), and reduce that to 1/8lb/ft3 of
fiberfil to the first one third of the horns length.
