Dual 120mm to 4 Inch Duct AdapterI designed this to exhaust my enclosure after growing tired of the buzz & noise provided by an actual duct fan (which is between 55 and 65db). I'm running 2 Noctua Redux-1700 PWM fans between 6 and 7.5 volts and it manages to push through 2 draft blockers (Canada Woo!) and about 25 feet of 4 inch ducting (with 3 elbows and 2 bent flexible ducts) with ease.

I've included 2 high quality versions of the model but I've only tested V1 at this time. V2 was designed to try and limit turbulence in the reduced section. All of the mounting holes will work with standard fan mounting screws

2022-06-14 - Added an underside duct to concentrate the incoming airflow. I've installed mine inside the cabinet and it provides a minor improvement to output airflow when running both fans under 9 volts with the V2 duct. Also note that, V1 is the better option when running both fans at or above 12v.

FYI - The duct shown in the photo was the prototyped version, the models here have been refined to look less block!

2025 update - 3 inch and 6 inch versions of this model are now up on my page

Layer height: 0.2-0.3mmNozzle: 0.4mm (0.6-0.8mm*)Shell count: 2-3Top Bottom Layers: 4-5Supports: NoneWalls: 2-3 (I printed mine solid with 5 walls no infill)Fill density: 0-20% (mostly for the bottom plate, increase bottom layers if you want to set to 0%)Print Method: FDMMaterial: PLA, PETG, ABS (Stiff when cool filament recommended)Material Quantity: about 150g (V1) 180g (V2)Print Time: approximately 16 hours with a 0.4mm nozzle

*If you want to use a 0.8mm nozzle, make sure you have adequate cooling, a 0.6 nozzle would be the better option for a print time reduction after my personal testing.