The NF-A14x25 G2 PWM Sx2-PP is a set of two NF-A14x25 G2 PWM square-frame 140mm fans that are offset in speed, which can be beneficial in push-pull operation as well as in situations where two fans are operating side by side, such as in case cooling applications or on 280mm water cooling radiators.

According to Noctua, when two fans are running at almost the same, constant speed in a push-pull configuration or, albeit to a lesser extent, side by side, 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-A14x25 G2 PWM fans contained in the Sx2-PP set are slightly offset in speed (+/- ~25rpm) 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 leverage extra torque headroom to keep the exact desired speed even when working against significant flow resistance such as on water cooling radiators and 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 optimize 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.

The retail package is somewhat bigger since now two fans are included. Again lot of information is displayed at the front and the back of the box.

Everything is well packaged and secured.

Inside the box users will find

• 1x NF-A14x25 G2 PWM PPA
• 1x NF-A14x25 G2 PWM PPB
• 2x NA-RC16 Low-Noise Adaptor (L.N.A.)
• 1x NA-YC1 4-pin PWM splitter cable
• 2x NA-EC1 30cm extension cable
• 8x NA-AV2 anti-vibration mounts
• 2x NA-AVG2-LR anti-vibration gasket for water cooling radiators
• 8x Fan screws

As with previous products, the G2 PWM Sx2-PP has typical dimensions 140x140x25 mm, packs two 4-pin PWM cables with 20cm of length, and inside the accessories box you will also find a 30cm NA-EC1 extension cable in case you need it. The rotation speed is 1500 RPM (1250rpm with L.N.A reducer), and by design one fan runs ~25rpm slower (PPA) and one ~25rpm faster (PPB) to counter noise and vibration levels. Each fan boosts an airflow of 155.6 m³/h (127.1 m³/h with L.N.A reducer) and the measured acoustical noise is 24.8 dB(A) (19.7 dB(A) with L.N.A. reducer). The operating voltage is 12 V and Noctua feels very proud that the product can reach an MTTF > 150,000 h.

Lastly, below we can see some installation examples of how the dual pack can be used in liquid coolers.