... printed optional 3.High decible and mellow sound,power amplifier function4.360 degree surround sound.booming bass ... stereo audio output,resonance of a subwoofer with superior bass experience6.With microphone output,suitable for outdoor using,like ... compatibility with various playback devices8. With bulit-in 500mAh high power capacity battary,long operation time9.Built-in battery,supply power with usb ...