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Noctua NF-S12B ULN, FLX

The next two new fan models that we will review and test come from the Austrian Noctua Company known for their scientific approach to any cooling system component, such as a heatsink plate or a fan blade. Frankly speaking, we can’t really call Noctua NF-S12B ULN, FLX fan new, because they are in fact enhanced and improved modifications of the NF-S12 fan that has already been discontinued.

The boxes are designed in Noctua’s traditional manner: highest quality and maximum functionality. It has everything: a cut-out window in the cardboard panel to attract the potential customer, a plastic casing inside that should protect the fan against transportation and other damages, an in-depth description of the fan features, including its detailed specifications:

Moreover, the back of the box can be unfolded to reveal even more details on the fan features and employed technologies:

Noctua NF-S12B FLX fan comes bundled with four silicone mounting spindles, four self-tapping screws, a PATA power connector and two adapters with built-in resistors lowering the voltage to 7 V and 5 V respectively:

The ULN accessories bundle is exactly the same, but without the 5 V adapter, not required for this particular fan model.

The fans can’t boast remarkable exterior, although they do look unique against the background of black and clear solutions. The fan frame is of light-beige color, while the fan itself is dark-brown:

The fan is 120x120x25 mm big, its weight is not specified. Each fan has 7 blades and a rotor with 41 mm diameter. The braided cable that comes with it is 400 mm long:


The key feature distinguishing the new fans from the old NF-S12B is the so-called “Bevelled Blade-Tips”. The front side of the fan blades is longer, while the tips have three specific notches on them:

According to Noctua engineers, this blade design increased the airflow from the fan as well as the pressure by 10%. Noctua engineers claim that the new NF-S12B FLX and ULN work quieter and create higher airflow than NF-P12 fan model, although I have to say this is hard to believe. However, FLX and ULN should actually lose to NF-P12 solution in static pressure, which is quite logical keeping in mind the shape of the blades.

ULN fans can work at 1200, 900 or 600 RPM depending on the resistor. The FLX version supports 700 and 500 RPM modes. As usual, Noctua provides the airflow values in cubic meters per hour. In cubic feet per minute these values look as follows: 59 CFM for ULN and 33.4 CFM for FLX at maximum rotation speeds. The static pressure is promised at 1.31 mmH2O for the top model and 0.44 mmH2O for the junior one. The latter should generate maximum 6.8 dBA of noise, while the ULN modification of the NF-S12B fan can produce as much as 18.1 dBA.

The new fans use the same bearing called Noctua SSO bearing, which is a fluid dynamic bearing with a magnet. A bearing of this kind equipped with a magnetic stabilizer of the rotor axis increases the fans MTBF up to 150,000 hours. This way Noctua can provide 6-year warranty for their fan products.


As for the electrical specs of the NF-S12B FLX and ULN fans, we could point out their low current and power consumption. The ULN model requires only 0.05 A and 0.6 W, while the faster FLX model needs precisely twice as much. The new fans are pretty pricy and go for $25 each.

Since Noctua themselves compare NF-S12B FLX and ULN against NF-P12 fan, we decided to add the results for the latter into our charts for a more illustrative comparison:

The new fans turned out better than NF-P12 in airflow. As you can see from the charts, despite the developers’ claims, the nine-blade model with larger sweep area pumps more air through than a fan with seven flat blades, even though they feature an enhanced tip. However, in terms of acoustics, NF-S12B FLX and ULN outperform their fellow fan. And while we have no complaints about the acoustic comfort provided by the ULN modification, the FLX one generates low-frequency rumble that is most likely generated in the gap between the blades and the fan frame. The bearing is extremely quiet. The subjectively comfortable acoustic range for the NF-S12B FLX model is around 900 RPM, while ULN model works quietly within the entire supported operational range. The power consumption of both models is really low and is very close to the declared values. Fans startup at 3.9 and 4.5 V, while NF-P12 required at least 6.6 V.

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