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Smooth Commutation Drive

Next to aerodynamic noise and bearing related noises, the so called "commutation noise" or "switching noise" can play a major role in the noise emission of axial fans with brushless DC motors. At each transition from one stator coil to another, the rotor receives a sudden torque pulse when the next coil switches on. Each of these torque pulses causes a minute deformation of the whole fan structure. Depending on rpm, torque and the material of the fan, this can result in noticeable noises.

Noctua's Smooth Commutation Drive system provides more continuous switching in order to achieve a smoother transition between the stator coils and thereby significantly contributes to the fan's overall quietness. The second generation of this technology (SCD2) further improves running smoothness and reduces minute noises in close proximity to the motor.


Noctua
05.03.2015 - ThinkComputers.com NH-D9L
Test verdict: "If you are building a small form factor system or even have a rackmount system and you are looking for a good air cooler that will not have any size restrictions then the NH-D9L is a great choice." (Bob Buskirk, ThinkComputers.com)
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03.03.2015 - FunkyKit.com NH-D9L
Test verdict: "The Noctua NH-D9L packs alot of cooling in a little package. If you are needing to save the space but do not want to sacrifice performance the dual fan setup competes pretty close to the big behemoth coolers." (Chris McCart, FunkyKit.com)
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03.03.2015 - PureOverclock.com NF-A4x10 5V
Test verdict: "Overall, I believe Noctua makes an excellent product. There really isnít anything I can complain about except for the price, and even then the price is understandable. If you need good air flow, low noise and have a small form factor case that needs some better fans, I could definitely recommend what Noctua has to offer here." (Josh Jackson, PureOverclock.com)
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03.03.2015 - FrostyTech.com NH-U9S
Test verdict: "Given these height and footprint size restrictions, the Noctua NH-U9S is a pretty quiet heatsink that offers very good thermal performance in the sub-125mm tall heatsink category, making it an excellent choice for PCs which are severely space limited. The results are enhanced by adding a second fan, as we've shown over the course of this review. Couple that with awesome build quality and a 6 year warranty and it's not hard to recommend this cooler." (Max Page, FrostyTech.com)
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