Hmm... Sorry for my late. I miss the thread
DX is the newest series of Nanoxia fans. I believe DX are an improvement from FX.
DX have no Watercooling and Removeable Fanblades like FX. It means the product is cheaper
New feature of DX is the improved ECO Traction and the Glassfieber Frame.
The Ecotraction is proved to be a Ultrawiderange Electronic Design so, no noise doesn`t matter which Voltage or RPM you run. Well, You might just hear the air moving.
I'll test them a bit deeper and compare to the latest fans from Enermax and Noctua