Closer Examination

The Noctua NF-A12x25 G2 is a 120 mm square frame fan that is 25 mm in thickness, meaning it should fit in pretty much all PC cases and cooling solutions intended for 120 x 120 mm fans. While at first glance it may seem similar to the predecessor NF-A12x25, mostly owing to the color scheme, even a cursory look will show the rotor is completely redesigned. The blades are wider and scoop more air volume through, especially in conjunction with those channels formed on each blade that act as flow accelerators along the leading edge. As before, we see the use of LCP (liquid crystalline polymer) for the rotor section to help reduce material expansion with temperature and rotational forces, as well as dampen acoustics based on the specific formulation used. This is also how you see the blades get so close to the inner frame, effectively maximizing the surface area for the airflow field to be pushed through. The hub is updated too, with Noctua referring to it as the Centrifugal Turbulator hub thanks to its own channels to increase the air being pushed near the hub where usually fans suffer most. Noctua retains its AAO (advanced acoustic optimization) frame here from before, complete with the silicone rubber anti-vibration corner pads, the stepped inlet, and the dents in the inner frame that reduce undesired turbulences. There are arrows on the side to help indicate both the direction of the blades rotating and that of the air flowing through.


From the back we see a 4-way stator vane configuration leading from the hub and placed perpendicular to each other as usually seen with PC fans. Noctua continues to use its SSO2 fan bearing here we saw put to good use in the predecessor. This is a sealed bearing with a brass shell, based off a fluid-dynamic bearing, and with an additional magnet to add stability when the fan blades are rotating. The motor is new though, with what Noctua calls the etaPERF motor used here and in the NF-A14x25 G2, with increased efficiency in terms of providing higher torque at the same power draw. There is an integrated Hall effect sensor in this updated drive system, and these help the fan spins at a specific RPM no matter the airflow restriction it faces—within practical reason, of course. This technology is called SupraTorque, and is how Noctua is willing to put out the two fan SKU that it guarantees will be offset in RPM by a specific value. This can be especially handy when using these fans on high airflow restriction radiators or heatsinks, where the fan RPM usually drops by a big margin compared to in an open environment.

Each fan is rated for 0.15 A (1.8 W) on the 12 VDC rail, which corresponds to the peak draw with start-up boost. You should be able to operate a good number of these fans off a single 1 A fan header on a decent motherboard. Alternatively, you can also get a powered PWM splitter and leave nothing to chance by powering the fans directly through the PSU. Noctua also mentions that the PWM motor used is based on their own custom-designed IC with a zero-RPM mode at 0% PWM duty cycle, and lowered PWM switching noise. The fan has a single power cable since, well, there are no LEDs or screens anywhere to be seen. The cable is sleeved just past the edge of the fan frame, is done in a heat-shrink application, and terminates in a 4-pin fan connector to be plugged into any standard 4-pin PWM header. The cable is 20 cm long, which is on the shorter side for most full-tower cases that support watercooling, but works well in combination with the supplied 30 cm long extension cable if you need it.