For those who put a second fan in front:
I picked up a few different fans to try: Arctic F12 can only be installed in one direction (push, not pull), Enermax has four pins connector, but connector has two small plastic rails which prevent the connector to fit pins (I did not try to push it hard yet) and Corsair air SP120 has just 3 pins, so no PWM. Anybody had trouble with fitting regular fans connectors with Ants pins? Did the second fan in front even helped?
The Antminer's fan pinout has a tab that's too long for normal fan connectors. I used the
bgears b-Blaster 120 with it and snipped off one side of the guard with wire cutters. I used this particular fan because I've used them as CPU coolers on my PC for years, and they're cheap, quiet, long-lasting, and move a good amount of air. It seems that the back fan has to work a little less hard with it, and is quieter overall with one of these pulling air.