I designed a simple housing for an activated carbon filter from the car accessories. The advantage is the large area. This has a large air passage and thus little resistance and allows the installation of up to three fans with a diameter of 120mm.

All parts must be printed 2x. I glued the frame parts with superglue.
The gasket is printed from TPU.
The two clamps ensure that the air filter does not curve. The matching activated carbon filter is from the car accessories and is for various Audi and VW models. It should have the dimensions 388mm x 150mm x 26mm. I used this model: PURRO PUR-PC0012C