Ground Zero GZIB 3000XSPL has Iridium-series GZIW 12SPL driver that is a real diamond in its price class. This enclosure uses EFP ( Enchanced Flow Port ) port. It has cross-section like aeroport. This gives significantly better air flow without side effects. More air throught the port = more bass! Despite the better air flow in same size enclosure, tuning frequency is the same than before.