... stereo amplifier, pro audio equipment, professional power amplifier, professional audio sound equipment, pro audio sound system, pa audio amplifier system, ... jack of active subwoofer, adjustable frequency of subwoofer.5.Active subwoofer manage-decline the volume of subwoofer by microphone or ... adjusting, reliable function lock,and parameter storage.13.Reliable SMT.14.Parameter displayed by LCD.15 ...