The NF-A12x25r is a round-frame version of Noctua’s award-winning flagship model 120mm NF-A12x25 fan. Its round shape makes it ideal for use on low-height dual-tower CPU coolers like the NH-D12L as well as other space-restricted applications that cannot accommodate square-frame 120mm fans. Just like the square NF-A12x25, the round NF-A12x25r uses a record-tight tip clearance of only 0.5mm, which is made possible by using the novel Sterrox® liquid-crystal polymer (LCP) compound as well as a metal-reinforced motor hub and axis for ultimate precision. Sharing the same state-of-the-art impeller design with Flow Acceleration Channels, the NF-A12x25r achieves the same class-leading quiet cooling performance as its square-frame sibling. It also supports fully automatic speed control via PWM fan headers and comes with a Low-Noise Adaptor to reduce the maximum speed from 2000 to 1700rpm. Topped off with exceptional running smoothness, Noctua’s reference-class SSO2 bearing, a rich bundle of accessories and 6-year manufacturer’s warranty, the NF-A12x25r is a premium-quality product through and through. Its superior efficiency, cutting-edge construction and pioneering materials make it an elite choice for all 120mm applications that require a round frame. Award-winning NF-A12x25 impeller Noctua’s NF-A12x25 has captured the hearts of quiet cooling enthusiasts around the world and reshaped the common perception of what 120mm fans can do. With more than 100 awards and recommendations from the international press, it is widely considered to be the best 120mm fan on the market. The NF-A12x25r combines the same impeller with a round frame. Round frame design The NF-A12x25r is identical to the NF-A12x25 except for its round frame that allows it to be used in applications where a square-frame 120mm fan would not fit. For example, the NF-A12x25r is ideal for being sunk in between the dual towers of the low-height NH-D12L cooler without causing compatibility problems with tall motherboard heatsinks or shrouds. Next-generation performance Noctua’s 120mm fans such as the NF-F12 and NF-S12A are renowned as being among the best on the market and have received more than 400 awards and recommendations from the international press. With its further improved efficiency and novel, state-of-the-art engineering, the NF-A12x25 represents another step up in performance and manufacturing. Highly optimised P/Q curve for all applications The NF-A12x25’s sophisticated aerodynamic design allows for a pressure to airflow (P/Q) curve that is extremely strong in the critical mid-section. This means that the NF-A12x25 is a true jack-of-all-trades with excellent performance in both static pressure demanding and airflow demanding applications. Excellent on-application acoustics While many fans produce unpleasant, high-pitched noises when installed in typical applications such as on heatsinks or radiators, the NF-A12x25 has been carefully fine-tuned for optimal on-application acoustics. It produces a smooth, pleasant frequency profile and surprisingly low sound pressure levels (SPL) when working against back pressure. Flow Acceleration Channels The NF-A12x25 impeller features suction side Flow Acceleration Channels. By speeding up the airflow at the crucial outer blade regions, this measure reduces suction side flow separation and thus leads to better efficiency and lower vortex noise. Ultra-tight tip clearance The NF-A12x25 has a record tight tip clearance (distance between the blade tips and the inside of the frame) of only 0.5mm. This highly ambitious design sets a new benchmark for 120mm fans and helps the NF-A12x25 to work more efficiently against back pressure, such as on heatsinks or radiators, by reducing leak flows through the gap between impeller and frame. Metal-reinforced motor hub The centrepiece of the NF-A12x25’s motor hub is made entirely from steel and the axle mount is reinforced with an additional brass structure. In combination, both measures ensure ultimate precision and increased stability in the critical hub area. Sterrox® liquid-crystal polymer compound The NF-A12x25’s impeller is made from Noctua’s novel Sterrox® liquid-crystal polymer (LCP) compound that features extreme tensile strength, an exceptionally low thermal expansion coefficient and damping characteristics that are ideal for reducing resonance and vibration phenomena in advanced fan-blade designs. AAO frame Noctua's AAO (Advanced Acoustic Optimisation) frames feature integrated anti-vibration pads as well as Noctua's proprietary Stepped Inlet Design and Inner Surface Microstructures, both of which further refine the fan's performance/noise efficiency. Stepped Inlet Design Noctua's Stepped Inlet Design adds turbulence to the influx in order to facilitate the transition from laminar flow to turbulent flow, which reduces tonal intake noise, improves flow attachment and increases suction capacity, especially in space-restricted environments. Inner Surface Microstructures With the tips of the fan blades ploughing through the boundary layer created by the Inner Surface Microstructures, flow separation from the suction side of the blades is significantly suppressed, which results in reduced blade passing noise and improved airflow and pressure efficiency. Integrated anti-vibration pads Integrated anti-vibration pads made from extra-soft silicone minimise the transmission of minute vibrations while maintaining full compatibility with all standard screws and other mounting systems. SSO2 bearing The NF-A12x25 features the further optimised second generation of Noctua's renowned, time-tested SSO bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability. Metal bearing shell In order to guarantee the highest possible degree of manufacturing precision, minimum tolerance and excellent long-term stability, the NF-A12x25 sports a CNC milled bearing shell made entirely from brass. Custom-designed PWM IC with SCD Supporting fully automatic PWM speed control, the fan uses Noctua's custom-designed NE-FD1 PWM IC that integrates Smooth Commutation Drive (SCD) technology. By providing smoother torque impulses, SCD suppresses PWM switching noises and thus makes the fan quieter at low speeds. Stops at 0% PWM When the fan is set to 0% PWM duty cycle by the motherboard or PWM fan controller, it will stop. This makes it ideal for creating setups with semi-passive cooling that automatically turn the fans off and thus run completely silent at idle if thermals allow. Smooth Commutation Drive 2 The latest version of Noctua's advanced Smooth Commutation Drive system ensures superb running smoothness by eliminating torque variations and switching noises. This makes the fan remarkably quiet even at very close distances. Low-Noise Adaptor The NF-A12x25 PWM is supplied with a Low-Noise Adaptor (L.N.A.) that reduces the maximum fan speed from 2000 to 1700rpm. The L.N.A. can be used either to run the fan at a fixed speed of 1700rpm or to cap the maximum speed when using automatic PWM control. Extensive cabling options The fan's short 20cm primary cable minimises cable clutter in typical applications while the supplied 30cm extension provides extended reach when necessary. Both cables are fully sleeved and a 4-pin y-cable allows the connection of a second fan to the same PWM fan header for automatic control.
