soundstream..... sst6x9 的speaker 好棒~~! 2 channel is typically for the subs, amps thats it.. a 4 channel is typically for four speakers of the car.. so better specific ohms . frequency sent to specific speaker therefore better background sound.. etc etc 你wiki wiki or 百度吧.. 我真的不会用中文讲... or 请大神出现说明