i want to put a reostat on my Y S tech 120mm fan. hope can decrease the loudness!! i saw 3 wire on it and i know the white wire are use for speed sensor. now the problem is should i put the reostat on red color wire or white color wire?? i'm not familiar with those electrical stuff, so anyone please help!! oh by the way, what kind of reostat should i get, how many ohm??