Answer

The KSub is a single chamber 4th Order Bandpass system that is optimized for compactness and portability. In order to achieve cardioid coverage, the KS212C Cardioid Sub requires a somewhat larger foot-print. It also uses a dual-chamber, 6th Order Bandpass design with one compartment firing forward while the other is rear-firing. Additionally, the increased enclosure volume of the KS212C produces greater low-frequency extension compared to the KSub.