Double 15 "speaker means that there are two 15" speaker units in a speaker, and single 15 "speaker means that there is one 15" speaker unit in a speaker. From the perspective of sound propagation, the effect of double 15 speakers will be twice as strong as that of single 15 speakers.

Audio is responsible for converting electrical signals into acoustic signals for people's ears to listen directly. It has to deal with people's hearing directly. People's hearing is very sensitive and has a strong ability to distinguish the timbre of complex sounds.