Fan adapter, 80 mm frame to 120 mm fan
A funnel-shaped shroud that fits a quieter 120 mm fan onto a case or power supply opening designed for an 80 mm fan. The small side is an 80 mm square with four 4.5 mm holes at 71.5 mm spacing, the large side a 120 mm square with holes at 105 mm spacing, and a smooth duct joins them over 30 mm with 2 mm walls. A curved rather than stepped inside transition cuts turbulence and noise, and a 1 mm lip on the small side seals against the panel.
Cases and fans come in 40, 60, 80, 92, 120 and 140 mm, and SpeakCAD builds the shroud between whichever pair you name, at the depth your case allows. Preview it free in your browser, then request a shallower duct, an offset centre or a finger guard grille.
Design a fan adapter shroud from 80 mm to 120 mm. Small flange 80x80x3 mm with four 4.5 mm holes at 71.5 mm spacing. Large flange 120x120x3 mm with four 4.5 mm holes at 105 mm spacing. Curved duct 30 mm long, 2 mm walls, 1 mm sealing lip.