1.Hot 4.1 amplifier speaker 2.4.1ch circuit design 3.USB, ... 4.OEM service 5.VFD display New design 4.1 amplifier speaker 1.Hot 4.1 speaker , solemn and delicate ... intensity, effectively eliminate resonance and cabinet noise5. With Standby,Input,Menu,VOL+,VOL- keys on the front panel. Output ... 20FT660 sets 40FT1380sets 40HQ1632 sets Hot 4.1 amplifier speaker with USB/SD/FM function and VFD display