I found this site for professional microphone solutions. Note here for myself. We filmmakers always need to explore new things.(even though I am not sure that I can call myself a filmmaker)Audio, cinematography, Music, Act etc. Before, I know the area of sound record not much. Maybe I just can be an appreciatory man. But if I can understand more, I will have more possibility to try. Is that right? It's never too old to learn. hehehehe... 3:1 rule This rule deals with phasing problems when summing a number of microphones to mono. The rule states, that the mutual distance between numerous microphones should be 3 times the distance between sound source and microphone. 無意中看到一個專業麥克風網站, 這方面還有很多可以學習的, 把三一律解釋放進來, 做個引子.