4" no speed controller, it sounds just louder than an air purifier on high, if I close the closet door I can't hear it. I put the filter in the tent, at an angle with a 90 elbow through the top hole, fan sits on top of tent outside, then I have some duct pushing exhaust out the door, the filter sucks out, because I choose to put it inside, my light sits 2" below filter, only giving me a maximum plant height of 23".