KMT21 is much more than a standard 21" powered pro audio subwoofer system. The amplifier mounted on board is Class D, delivering 2 x 2400 W at 4 Ohm. It's usable as PA sound system for live concerts and dj sets but it's also suitable for various kind of temporary or permanent intallations. The unique four-corner port configuration gives symmetrical back loading to the speaker for extended bass response with very low distortion. This also gives incredible structural strength to the cabinet despite its light weight. The rear panel provides input for a balanced line signal, a balanced microphone signal with phantom power and digital signals in AES/EBU protocol and also on an XLR for ease of cabling.