A speaker design technology acquires a coaxial effect of an output sound by placing a high-frequency speaker for outputting a high-pitched sound apart from a low-frequency speaker for outputting a low-pitched sound by a predetermined distance and mechanically arranging output points of the high-frequency speaker and the low-frequency speaker in alignment with each other. The speaker design technology lets vibration of a low-frequency speaker to avoid interference by the high-frequency speaker and also lets the high-frequency speaker to avoid interference by the vibration of the low-frequency speaker by arranging the high-frequency speaker in front of a dust cap necessarily installed in the center of the low-frequency speaker. Since the high-frequency speaker and the low-frequency speaker are spaced apart from each other so as to independently operate, any interface is not required for enabling the high-frequency and the low-frequency speakers to interwork with each other.