The fan as been chosen from the requisites of the filters. The filters are rated for a amount of air flow and oppose some resistance. When they get dirty, the resistance increase as well. The fan is powerfull enough to deliver air pressure up to the max rated by the filters.

I made a mistake when buying the fan. It is no dimable. It's either full power (and noisy) or off.

The fan is inside a crate, creating a depression behind the filters and the exhaust is located one one side.