We measured the noise level of our coolers throughout the entire speed range of their fans, as described in the chapter on testing methodology. Here are the results:
Most of the noise in Zalman CNPS9900DF comes from the 135 mm fan. The smaller fan is inaudible against its background. The cooler itself could be considered moderate in terms of noise levels, even though it is significantly behind Thermalright TRUE Spirit here, however, the rattling of the 135 mm fan motor becomes very distinct in the interval between 600 and 1050 RPM. The bearings and the airflow created by two fans do not make Zalman CNPS9900DF acoustically uncomfortable in any way, but the rattling of the motor starts getting on your nerves 3-4 minutes in. Therefore, we can’t consider Zalman CNPS9900DF acoustically comfortable or quiet, although the graph shows the readings at 940 and 740 RPM fall into acoustically comfortable and quiet range, respectively. Unfortunately, it doesn’t matter, because the rattling motor diminishes it all. It could be the peculiarity of our specific cooler sample, though.
Zalman CNPS9900DF turned out a real beauty, which would fit perfectly into the holiday concept and please your guests with unique shape and very nice blue lighting. Its indisputable advantages are full universality, reliable and informative packaging, and highly efficient thermal paste among the bundled accessories.
As for overclockers and quiet cooling fans, Zalman CNPS9900DF will be an attractive, yet expensive choice. Its efficiency is pretty modest and it most likely won’t let you unveil the entire overclocking potential of your processor. Moreover, very challenging installation procedure will hardly help this cooler win more users, especially beginners. Also, I have to bring up the rattling issue once again.
So, I have to admit that though Zalman CNPS9900DF will be a great addition to an open stand or modding system cases with clear side panels, it may not be able to cope with heavily overclocked processors especially in case of strict noise limitations. But, as always, it is up to you to decide, whether the advantages outweigh the concerns.