4 fans? Hardcoreeee

Yes, With that I can mine at 750w (10 TH/s) with only 45db.

Oh nice! Curious to see how that compares to upgrading to 2x 140mm fans instead. I might swap one of my miners to 4x stock fans and do a side by side comparison. Did you just use a pair of splitters to power the extra fans?

Yes, two splitters, one for the front and one for the back.