Excerpt: Today we're going to take a look at two Noctua case fans that look identical but are designed slightly different for different computer operating requirements. The first fan we want to test is the Noctua NF-S12B ULN . This fan runs at two different speeds; 700 RPM or 500 RPM. The main feature of this particular fan is that it is designed to run as quietly as absolutely possible and still cool your computer components effectively.
Pros: Practically silent operation, cools effectively at the low speeds.
Cons: Pricier than other 120mm fans. Does not cool as effectively as other higher speed 120 mm fans and it would be nicer to have a built in resistor in the fan with a switch that can be accessed from the back of the PC instead of having to switch adapters every time you want to change the speed.