Noctua NF-A12x25 (FLX, PWM, ULN) Review (Page 2 of 4)

Page 2 - A Closer Look - Hardware

All three Noctua fans have the same exterior design, and so I only took pictures of one to simplify everything that is in the image. Pictured above is the PWM version of the NF-A12x25. The difference between them is both the PWM and ULN versions are PWM controlled, while the FLX version is voltage controlled. The ULN version has a lower maximum speed. In my opinion, buying the PWM version will get all your problems solved, since you you can cap its RPM and convert it to a voltage controlled fan with the included accessories. Each of the fans feature the same traditional color scheme Noctua fans have had for ages, which is a nice change from the RGB madness we have going on. The light tan and brown have made a mark on the enthusiast market, even though it is extremely difficult to fit these fans into any other color scheme. I really hope someone makes a Noctua-themed PC one day. Secondly, the fan motor in the center of the fan is bigger than the NF-A12x15. As well, the size of the individual fan blades are also larger and closer together, which is due to the normal sizing. The NF-A12x15 was meant to have a smaller profile. When it comes to the large center hub, it is made entirely of steel, while the axle mount is reinforced with brass. The weight of the fan reflects this excellent build quality, and Noctua is confident this fan will last, as they back it up with a six-year warranty. Furthermore, they are rated at an MTTF of 150,000 hours, which is about seventeen years. MTTF stands for Mean Time to Failure, meaning it is the average amount of time this fan can run before failing.

The NF-A12x25's center hub is not the only piece of the fan that exudes quality. The frame of the fan is Noctua's AAO frame, which stands for Advanced Acoustic Optimization. This is the integrated anti-vibration pads, Noctua's Stepped Inlet Design, and Inner Surface Microstructures. According to Noctua, this should refine the fan's performance and the noise efficiency. Needless to say, Noctua makes every effort to ensure an excellent and quality product in its construction.

Here, we have a close-up of some of the smaller engineering components. The main focus of this picture is what Noctua calls Flow Acceleration Channels. According to Noctua, this increases the airflow at the outer edges of the impeller. The NF-A12x25 then has reduced suction side flow separation, which increases efficiency and lowers vortex noise. Furthermore, the impellers are extremely close to the frame, which has an ultra-tight tip clearance of only 0.5 mm. This is the smallest distance between the impellers and frame that Noctua has ever had, which makes the fan much better in heatsink and radiator applications. More air can be pushed through the radiator instead of leaking through a large gap. With the Noctua NF-A12x15, one could see the small microstuctures on the frame of the fan, but with the NF-A12x25, these cannot be seen. I only realized they were there because Noctua said so, and only then did I feel them when I ran my finger along the frame. In the correct lighting, you can also see them. The impellers themselves are made out of a Sterrox liquid-crystal polymer compound, which has excellent tensile strength, low thermal expansion, and dampening characteristics. These work together to reduce resonance and vibrations.

To cover some specifications, the Noctua NF-A12x25 has a 25 mm thickness, and then of course is 120 mm in its other dimensions. Starting with the PWM version, the max RPM is 2000, but if the low-noise adapter connector is connected, the RPM is limited to 1700, while the minimum RPM is 450. The airflow is rated at 102.1 m3/h, acoustical noise comes in at 22.6 dB(A), and the static pressure measures in at 2.34 mm H2O. With the low-noise adapter connected, these numbers change to, 84.5 m3/h, 18.8 dB(A), and 1.65 mm H2O. All of these specifications are impressive, but we will have to see how well it all works on the next page. Next, we have the ULN version with a max RPM of 1200, but with the ultra-low-noise adapter connected, that RPM is limited to 900. Airflow comes in at 55.7 m3/h, but with the ULNA adapter, it goes down to 39.4 m3/h. The acoustics are measured at 12.1 dB(A), but with the ULNA, it is 7.6 dB(A). Static pressure is 0.82 mm H2O, and with the ULNA, it is 0.41 mm H2O. The FLX version has a 3-pin connector, but with three speed settings. I am going to start with the settings without any connectors attached. The max RPM is 2000, airflow is 102.1 m3/h, acoustical noise is 22.6 dB(A), while the static pressure comes in at 2.34 mm H2O. With the LNA attached, these specifications change to 1700 max RPM, airflow is 84.5 m3/h, acoustical noise is 18.8 dB(A), and the static pressure is 1.65 mm H2O. Lastly, with the ULNA connected, the max RPM is 1350, airflow is 64.5 m3/h, acoustical noise is 14.2 dB(A), and the static pressure is 1.05 mm H2O.

On the back of the NF-A12x25, there is more information on the label. As you can see, this is the PWM model with a max RPM of 2000. Otherwise, one of the important features of fans are the bearing they use. For the most part, fans use sleeve or ball bearings. There are benefits and disadvantages to these types of bearings, as there are with anything. In general, sleeve bearings are quieter, but might not last as long as ball bearings. Noctua, however, uses their SSO2 bearing, which is a self-stabilizing oil-pressure bearing. The bearings are hydrodynamic and include a magnet, so the axis is stabilized with the magnetic field. This proves to have higher precision and better longevity than other conventional designs. Noctua has again delivered a fan with high quality materials and incredible specifications on paper. On the next page, we will be doing a bit of a test to see how the fans perform.

Page Index
1. Introduction, Packaging, Specifications
2. A Closer Look - Hardware
3. Performance Tests
4. Conclusion