1: F55B ultra-low frequency speaker is composed of a 15-inch high-performance, high-power, long-stroke bass unit of 220 magnetic steel with a 100-core voice coil. And a high power active power amplifier board enclosure structure adopted direct type design, combined with their German audio technology, make its low frequency high performance, plump and soft, deep, powerful and rich flexibility, sound field include feeling is wonderful, good overall lower limit, tone is pure natural, rich music rhythm, has very good resistance to listen to, provide the audience with a steady stream of low frequency. With the full frequency speaker will achieve the most ideal effect. 2: applicable venue: bar, Disco hall, slow swing bar, entertainment KTV rooms of ultra-low frequency speakers, nightclubs, dance halls, clubs, medium-sized mobile performance of the main ultra-low frequency expansion, conference hall, multi-function hall of the main ultra-low frequency expansion.