I did Prime95 test with top cover sealed & upper fan off and the temperatures/RPMs were same as with upper fan active, so, i've ordered 1x Noctua NF-P14s redux-900 to replace Fractal fan.

I never ever heard a fan below 200rpms inside a case ever, are you sure its those fans that you are hearing? maybe its the cpu fan or PSU fan? sometimes is even the hardrives that emit a sound that gets confused. Actually, it's sound like it's emited by fan itself, or it's bearing than airflow, for...

Hi, I have following build: Case: Fractal Design Core 500 CPU: i5 6600K Mobo: Asus Z170i Gaming PSU: Corsair RM550x CPU cooler: SilentiumPC Fera 2 HE1224 Rear, outtake fan: Fractal Design Silent R3 140mm Upper, intake fan: AC F12 PWM (1x) SSD So far, no GPU (waiting for GTX 970 sucessor) I want to a...