The third Chromax.Black product is the dual setup of 140mm fans, the NF-A14x25 G2 PWM Sx2-PP Chromax.Black. In this product, we will find two 140mm fans that are offset in speed, which can be beneficial in push-pull operation as well as in situations where two or more fans are operating side by side, such as in case cooling applications or on 280mm or 420mm water cooling radiators. Topped off with Noctua’s trusted premium-grade SSO2 bearing, more than 150,000 hours MTTF and a 6-year manufacturer’s warranty, the NF-A14x25 G2 PWM Sx2-PP chromax.black is the perfect choice for users who are looking for a dual 140mm fan set that combines cutting-edge quality, quietness, and performance in an all-black style.

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 (+/- ~50rpm) to avoid such phenomena. 

The accessories box includes many goodies

• NF-A14x25 G2 PWM PPA chromax.black
• NF-A14x25 G2 PWM PPB chromax.black
• 2x NA-RC16 Low-Noise Adaptor (L.N.A.)
• NA-YC1 chromax.black 4-pin PWM splitter cable
• 2x NA-EC1 chromax.black 30cm extension cable
• 8x NA-AV2 chromax.black anti-vibration mounts
• 2x NA-AVG2-LR chromax.black anti-vibration gasket for water cooling radiators
• 8x NA-AVP1-LR chromax.black load-relief anti-vibration pads
• Black fan screws

The fans have standard 140x140x25 mm dimensions and a 4-pin PWM with a 20cm + 30cm NA-EC1 extension cable option. The fan includes SSO2 bearing technology and a new design, which, according to Noctua, offers better performance/noise ratio compared with older designs and other manufacturers. The normal rotation speed is (+/- 10%) 1500 RPM, while with the included L.N.A. adapter, it can drop down to (+/- 10%) 1250 RPM. The performance numbers that Noctua provides are very good, with airflow 155.6 m³/h (L.N.A. 127.1 m³/h), acoustical noise 24.8 dB(A) (L.N.A. 19.7 dB(A)), and static pressure 2.56 mm H₂O (L.N.A. 1.3 mm H₂O). The product includes a 6-year warranty.

The two fans have different tags at the back, indicating the PPA / PPB tag to separate their minus 50rpm operation.