Noctua NF-A14x25 G2 PWM Sx2-PP 1500RPM 140mm Next Gen Push-Pull Fan Set

The NF-A14x25 G2 PWM Sx2-PP is a pair of 140mm fans with slight speed offsets to reduce noise-causing interference in push-pull or side-by-side configurations.

The NF-A14x25 G2 PWM Sx2-PP is a set comprising two NF-A14x25 G2 PWM square-frame 140mm fans with slightly offset rotational speeds. This design is particularly advantageous for push-pull configurations and scenarios where two fans operate in close proximity—such as in case cooling applications or on 280mm water cooling radiators.

When two fans run at nearly identical, constant speeds in a push-pull setup—or, to a lesser degree, side by side—their acoustic interaction can give rise to undesirable harmonic effects. These include intermittent vibrations and periodic humming caused by interference, which may manifest as beat frequencies. To mitigate such phenomena, the two fans in the Sx2-PP set are deliberately offset in speed by approximately ±25 RPM.

This fine-tuning is made possible by the fans’ innovative etaPERF motor in conjunction with the NE-FD6 driver IC, which allows for exceptionally precise speed control. Additionally, the motor’s SupraTorque feature provides extra torque headroom, ensuring stable operation at the intended speed—even under high airflow resistance, as encountered with water cooling radiators and heatsinks.

In practice, one fan (PPA) operates at roughly 25 RPM below the nominal speed, while the other (PPB) runs approximately 25 RPM above it. This modest differential maintains overall cooling performance while effectively reducing unwanted acoustic interference.

As perception of beat frequencies can vary according to individual psychoacoustic preferences, users are given the option to further refine the sound profile. This can be achieved by slightly reducing the speed of the PPA fan via PWM control or by using the supplied Low-Noise Adaptor, resulting in a smoother, more refined acoustic signature due to the increased speed offset.

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.

SSO2 Bearing

The NF-A14x25 G2 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.

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.

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 and airflow demanding applications.