A method to provide back sound channel loudspeaker just like an earphone wear on the head includes the following; providing analog earphone wear on the head or analog earphone device which has through opening to receive signal from forward loudspeaker with backward loudspeaker in it, then transmitting signal from forward, backward and heavy bass voice to correlated loudspeakers, at last signal being transmitted to backward loudspeaker to be processed by HFTR and device which creates virtual loudspeaker to obtain virtual loudspeaker at back side, and sending the processed signal to the backward loudspeaker. |