So I was looking for a solid, quiet alternative to the included Antminer S7 fans (I was just curious if it was possible or not), and I think I actually found them! They are these 3500 rpm, 150 cfm, 35 db max fans from Enermax called the Enermax D.F. Storm 120mm. They are PWM, but their connectors did not fit in the ones on the S7 (they could with a simple bit of sanding / cutting, but I was looking just to test their ability before I broke out the sandpaper
), so what I did is zip tie the original fans onto the shelf of my test bench type thing where the miner is running, plugged them into the board (and the Enermax fans into the included molex adapters) and dialed their speed way down through the online options. I can confidently say that while running a tad (8C) hotter at the stock speed of 4.3Th/S, these things are so quiet that it is completely worth it. I'm currently working on coaxing the S7 up to a small-ish overclock (if possible), so I will update this thread as I go along with anything new that may be interesting for you guys.
Here is a picture of my setup with these new fans (please excuse the cable mess
):
http://imgur.com/azcnXZI