The SUB400-amp is a compact self-powered subwoofer cabinet designed to extend the frequency range and power bandwidth of Audio Performance full-range loudspeaker systems. With a cut-off frequency of 25Hz, the SUB400-amp is made for applications where the reproduction of sub frequencies is of importance (music, sound effects).

It consists of two long excursion 18-inch cone drivers mounted in a heavily braced vented enclosure.