The predecessor models of the GZIB boxes were among the most successful on the market. No wonder, because in their price class they had a superior sound quality. New models feature new subwoofers that have been optimised with Klippel equipment. The drivers feature even impedance behaviour, good sensitivity and good power handling. These characteristics ensure good sound quality and plenty of bass at very moderate amplifier power. New, better drivers also deserve a better cabinet. Previous enclosures were so good that it was difficult to improve them. The solution was to invent a new type of port. This enclosure uses an EFP (Enchanced Flow Port) connector. It has a cross-section like an airport. This results in much better airflow without side effects. More air through the duct = more bass! Despite the better airflow in the enclosure of the same size, the tuning frequency is the same as before. And it delivers a very even bass response across the entire bandwidth. The size of the port is more than sufficient for the required amplifier power of this subwoofer. If you're looking for an active subwoofer that gives you good sound quality and plenty of bass, this is the one for you.