I picked up 4 of the S7's and immediately switched all the fans to Scythe UltraKaze which are probably my favorite fans for a variety of reasons. They spin at 3000 rpm putting out 133 cfm at a low 45 db. Not the cheapest but last forever. The last point is that they are great where static pressure is an issue, such as the tightly spaced fins on Bitmain products. I can now be in the same neighborhood as the S7's and hear my family talking.
Interesting, I loved the Kaze's with the S5's, but I've had pretty poor experiences with them so far with the S7... The stock fans for me are god-awful, one of the pairs resonates at high speed, and makes a really pleasant constant 'train whistle' sound - really adds to the whole experience. At 55% the sound is gone, but still lurking in the background.
I'm in the process of designing a ducted solution to mount a centrifugal blower - I think I can use only one and get better numbers and even quieter than a single Kaze, plus the static pressure of blowers smoke axial fans. The test blower I'm using can move 500cfm, but at the cost of static pressure and sound, but at more mellow values, like 200 cfm it's amazingly quiet.
My first pass is always to get a standalone solution, then I'll look to integrate the S7 into my big plenum case - the challenge with it is the fan I chose for it doesn't have the best static pressure because the S5's were so free-flowing, there wasn't a point - I'm not sure that will be the case with the S7's. I'm also holding off to design it into the case until J4bberwock's next PSU design, since I plan to use that and incorporate it into the design as well.
