The NF-A14x25r G2 PWM Sx2-PP is a set of two NF-A14x25r G2 PWM round-frame 140mm fans for push-pull operation on heatsinks such as the NH-D15(S) or NH-U14S. When two fans operate in a push-pull configuration running at almost the same, constant speed, their acoustic interaction can lead to undesirable harmonic phenomena such as intermittent vibrations or periodic humming due to interference, which can be heard as beat frequencies. Therefore, the two NF-A14x25r G2 PWM fans contained in the Sx2-PP set are slightly offset in speed (+/- ~25rpm) in order to avoid such phenomena. This fine-tuning is made possible by the fans’ novel etaPERF™ motor and its NE-FD6 driver IC that achieves extremely precise speed control and, thanks to its SupraTorque™ feature, can leverages extra torque headroom to keep the exact desired speed even when working against significant flow resistance such as on heatsinks. With one fan running ~25rpm slower (PPA) and one ~25rpm faster (PPB), the overall cooling performance can be kept the same while efficiently preventing intermittent vibrations or periodic humming. Since the perception of beat frequencies can vary depending on psychoacoustic preferences, users can easily further optimise acoustics by slowing the PPA fan down a little more through PWM control or the supplied Low-Noise-Adaptor, which will result in an even smoother sound signature due to the increased offset.

Details

Push-pull set

Push-pull set
Bundling two NF-A14x25r G2 PWM fans that are speed-offset by +/- 25rpm in order to avoid undesired acoustic interaction phenomena, the Sx2-PP set is the ideal choice for push-pull configurations on 140mm class coolers such as the NH-D15(S) or NH-U14S.

Next-generation performance

Next-generation performance
Noctua’s NF-A15 is renowned as being among the best round-frame 140mm fans on the market and has received more than 100 awards and recommendations from the international press. With its further improved efficiency and novel, state-of-the-art engineering, the NF-A14x25r G2 represents another step up in performance and manufacturing.

Highly optimised P/Q curve for all applications

Highly optimised P/Q curve for all applications
The NF-A14x25 G2’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-A14x25 G2 is a true jack-of-all-trades with excellent performance in both static pressure demanding and airflow demanding applications.

Excellent on-application acoustics

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-A14x25 G2 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.

Progressive-Bend impeller
Progressive-Bend impeller
The NF-A14x25 G2 features a unique Progressive Bend Impeller with Flow Acceleration Channels and winglets. Its nine blades are swept backwards close to the hub and progressively bent forward further out. Working in tandem with the Centrifugal Turbulator hub, this design not only helps to push more air towards the outer blade areas where efficiency is higher but also assures maximum lift and near uniform loading across the entire blade span.

Centrifugal Turbulator hub
Centrifugal Turbulator hub
Acting as a turbulator, the new Centrifugal Turbulator hub design improves flow attachment in the hub region. At the same time, it’s centrifugal driving motion pushes air outwards from the hub area where efficiency is low due to the slow rotational speed towards the outer, high-efficiency zones of the blades, thereby increasing overall efficiency by optimising fluid distribution across the impeller area.

Flow Acceleration Channels
Flow Acceleration Channels
The NF-A14x25 G2 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.

Winglets
Winglets
Winglets can help to reduce tip vortices that are caused by the pressure differential between the suction and the pressure side of fan blades but bear the risk of reducing efficiency due to extra fluid displacement in high velocity regions. The NF-A14x25 G2’s small winglets have been carefully fine-tuned to provide consistent efficiency gains working in tandem with its Progressive-Bend blade geometry, Flow Acceleration Channels and AAO frame.

Ultra-tight tip clearance
Ultra-tight tip clearance
The NF-A14x25 G2 has a record tight tip clearance (distance between the blade tips and the inside of the frame) of only 0.7mm. This highly ambitious design sets a new benchmark for 140mm fans and helps the NF-A14x25 G2 to work more efficiently against back pressure, such as on heatsinks or radiators, by reducing leak flows through the gap between impeller and frame.

Sterrox® liquid-crystal polymer compound
Sterrox® liquid-crystal polymer compound
The NF-A14x25 G2’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
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
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
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
Integrated anti-vibration pads made from extra-soft silicone minimise the transmission of minute vibrations while maintaining full compatibility with all standard screws and most other mounting mechanisms.

SSO2 bearing
SSO2 bearing
The NF-A14x25 G2 features the further optimised second generation of Noctua's renowned, time-tested SSO2 bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability.

Metal bearing shell
Metal bearing shell
In order to guarantee the highest possible degree of manufacturing precision, minimum tolerance and excellent long-term stability, the NF-A14x25 G2 sports a CNC milled bearing shell made entirely from brass.

etaPERF™ motor with NE-FD6 PWM IC
etaPERF™ motor with NE-FD6 PWM IC
Noctua’s new etaPERF™ motor sets new standards in energy efficiency thanks to its extremely low electric impedance and the latest NE-FD6 drive system with its integrated, ultra-sensitive Hall effect sensor that provides super-precise commutation performance. This not only enables it to convert a minimal electric input into a maximum power-output with hardly any losses, but also works in tandem with Noctua’s proven Smooth Commutation Drive 2 technology to make the etaPERF™ motor run near-inaudible.

SupraTorque™
SupraTorque™
Most fans become slightly slower when working against back pressure such as on heatsinks and radiators, which results in reduced performance. Enabled by the new NA-FD6 driver IC, Noctua’s SupraTorque™ technology allows the fan to leverage additional torque headroom when required in order to keep its RPM speed at the desired level no matter the airflow resistance, ensuring consistent performance even in the most demanding conditions.

PWM control with wide speed range
PWM control with wide speed range
The NF-A14x25 G2 PWM can be PWM-controlled from its maximum speed of 1500rpm all the way down to 300rpm. This makes it possible to adjust the fan for maximum performance or near-silent operation using either automatic, temperature-based motherboard speed control or manual controllers such as the NA-FC1.

Stops at 0% PWM
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
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
Low-Noise Adaptor
The NF-A14x25 G2 PWM is supplied with a Low-Noise Adaptor (L.N.A.) that reduces the maximum fan speed from 1500 to 1250rpm. The L.N.A. can be used either to run the fan at a fixed speed of 1250rpm or to cap the maximum speed when using automatic PWM control.

Advanced protection features
Advanced protection features
Protected against reverse polarity, over voltage and over current (short-circuits), the fan is suitable for use in challenging electrical environments. At the same time, its ultra-low EMC emissions make it ideal for applications where electrical interference is critical. Last but not least, its locked rotor and overloading protection add extra safety in situations where the fan may be blocked mechanically.

Extensive cabling options
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.

Safety certifications
Safety certifications
Unlike many cheap fans, the NF-A14x25 G2 has been thoroughly tested for electrical safety, immunity and radiated emission. Carrying CE, TÜV, UKCA and UL certifications and meeting all applicable standards (EN 62368-1, EN 55035, EN 55032, UL-507), it is a safe, quality device through and through.

6-year manufacturer’s warranty
6-year manufacturer’s warranty
Noctua fans are renowned for their impeccable quality and outstanding longevity. Like all Noctua fans, the NF-A14x25 G2 features an MTTF of more than 150,000 hours rating and comes with a full 6-year manufacturer’s warranty.