Hi I'm building a pc for $510 and i'm new to pc building so it is hard for me to find good case fans for a low price (I need 5 case fans) that are 120mm and are from a known, trusted brand, offer reasonable airflow and wont die in like 6 months. Does anyone know any good models? Any help would be appreciated thanks.
Every case I've ever seen comes with at least 1x fan, usually mounted at exhaust. Most cases come with 2x fans, 1x exhaust and 1 intake.
2x 120mm exhausts spinning at 600rpm and 2x 120mm intakes at 700rpm can give a balance or positive. 2x 120mm at 600rpm and 2x 140mm at 600rpm can give a negative. 2x exhausts at 1000rpm and 3x intakes at 700rpm can also give a negative.
Just adding a fan does not mean that you get positive or negative results. It depends on the fan curves and coefficient of cfm to rpm. Many high cfm fans even lack enough static pressure at lower rpm levels to change air volume one way or the other. With those fans, air really doesn't move unless moved by an exhaust fan.
It's entirely possible to have 2x exhaust and 3x intake and at idle have a negative system, at normal loads be balanced and at gaming loads be positive.