All said, the Cooler Master fans did well today. The Cooler Master Jetflo and Sickle Flow X outdid their specifications. The Jetflos matched their free-air specifications when pulling behind a filter. The Sickle Flow X exceeded their free-air specs behind a filter. There are plenty of fans out there that only just match their specs in this very same testing system, but the Cooler Master fans are better than that. Compared with the best fans one could throw at them, they did well.

Conclusion -- Jetflo

One unexpected benefit of these fans is the silence of their circuitry. One could expect the non-PWM Sickle Flow X to be silent, given its heritage and its construction. But the Jetflo is a PWM fan. Traditionally PWM fans click, a little or a lot. The Jetflos clicked not at all. Let us hope Cooler Master will put these silent circuits in all their PWM fans.

The sound pressure level when the noise-reducing adapters were applied was above Cooler Master specifications. This could be because the fans were going faster than specified. Given that users are looking for quiet when they apply these adapters, perhaps increasing the resistors slightly would bring down the fan speed, and hence bring down the noise. But still, these are not noisy fans.

Further reducing the noise of these fans are the cutaway frames and the rubber corners. Cooler Master doesn't make much noise about these features, but they really do work as designed -- they reduce vibration and vibration noise.





Conclusion – Sickle Flow X

The Sickle Flow X fans are prototypes. This seems surprising, since they came in retail boxes printed especially for them. The Sickle Flow blade shape has a gentle slope, a moderately broad chord and a highly swept leading edge. Given these features, one would expect the Sickle Flow to produce a fairly good static pressure fairly quietly, making it a good fan for radiators as well as heatsinks and cases. It does that, and has sold well for years – one of the Sickle Flows in this test dates from mid-2008!

Occasionally users complain about the Sickle Flow's sleeve bearing. It is sealed, but it is still a sleeve. This is where the Sickle Flow X represents a significant improvement. The POM bearing is rated for 160,000 hours – more than 18 years. While there are no definite plans to release this gem, we can hope that Cooler Master will decide to put the Sickle Flow X on the market. As with all Sickle Flows, they purr, and they sound quieter than their measured SPL.