Scythe Kaze Flex II 120 in detail
Clockwise rotation fans are quite a rarity, you don’t normally come across them. However, Scythe, for example, makes such models and for good reason. Why not take it the other way around? In terms of standalone operation, of course, it doesn’t matter. In series, in the position of the second fan, it is possible to achieve higher cooling performance on CPU coolers compared to using fans with the same direction of rotation.
First, a general look at the main ways in which the Kaze Flex II 120 differs from the vast majority of other models and how the opposite direction of rotation is beneficial.
All of the fans we’ve tested so far rotate from right to left, but the Kaze Flex II rotates clockwise. This in itself does not affect the aerodynamic properties, and while keeping the same shape, but with the inverse geometry (to keep the leading edges in line with the direction of rotation), the key parameters (airflow and static pressure) naturally do not change. Nevertheless, such a fan can contribute to increased cooling performance in certain systems.
For the reasons mentioned above, Scythe also has fans with different rotation directions, namely in dual-tower coolers with a (front-to-back) fan/fin bundle/fan/fin bundle scheme. When the second fan, clamped by the finned towers, rotates in the opposite direction to the front fan, it picks up more air, to use the vernacular. However, this is usually at the expense of higher noise and efficiency (in the sense of cooling performance per unit of noise) can be, and in the experience of manufacturers, does end up being lower. This may not always be true for all fan combinations across the entire speed range, but this is basically the main reason why the coexistence of fans with opposing rotations is a rare occurrence.
Clockwise rotating fans are also tackled, for example, by Thermalright (TL-C12C), which we’ll get to sooner or later as well. But now to the analysis of the Kaze Flex II 120.
The rotor consists of eleven, relatively shorter blades. These are quite stiff, they don’t flex too much, which can be seen in the low vibration at top speed (around 2000 rpm). These are partially damped, in terms of transmission to the frame, by the softer rubber corners.
The angle of the blades is greater as is the spacing of their tips from the frame, and the spacing between adjacent blades is not that small either. These are all indicators to the fact that the static pressure at equal noise levels will be rather lower.
The Kaze Flex II 120 is available in three variants with different maximum speeds. The slowest, KFS1225FD12-P model maxes out at 1200 rpm, the KFS1225FD15-P, which is also part of the Fuma 3, at 1500 rpm and the tested KFS1225FD20-P at 2000 rpm. At that speed, moreover, Scythe promises an enormous airflow of 153.39 m3/h. And we will already note that with increasing rpm the airflow of this design increases significantly, but this alongside it also the noise level.
And one more thing: To navigate through the result graphs as easily as possible, you can sort the bars according to different criteria (via the button on the bottom left). By (non)presence of lighting, profile thickness, brand, bearings, price or value (with the option to change the sorting to descending or ascending). In the default settings, there is a preset “format” criterion that separates 120mm fans from 140mm fans.
- Scythe Kaze Flex II 120 in detail
- Overview of manufacturer specifications
- Basis of the methodology, the wind tunnel
- Mounting and vibration measurement
- Initial warm-up and speed recording
- Base 6 equal noise levels…
- ... and sound color (frequency characteristic)
- Static pressure measurement…
- … and airflow
- Everything changes with obstacles
- How we measure power draw and motor power
- Measuring the intensity (and power draw) of lighting
- Results: Speed
- Results: Airlow w/o obstacles
- Results: Airflow through a nylon filter
- Results: Airflow through a plastic filter
- Results: Airflow through a hexagonal grille
- Results: Airflow through a thinner radiator
- Results: Airflow through a thicker radiator
- Results: Static pressure w/o obstacles
- Results: Static pressure through a nylon filter
- Results: Static pressure through a plastic filter
- Results: Static pressure through a hexagonal grille
- Results: Static pressure through a thinner radiator
- Results: Static pressure through a thicker radiator
- Results: Static pressure, efficiency by orientation
- Reality vs. specifications
- Results: Frequency response of sound w/o obstacles
- Results: Frequency response of sound with a dust filter
- Results: Frequency response of sound with a hexagonal grill
- Results: Frequency response of sound with a radiator
- Results: Vibration, in total (3D vector length)
- Results: Vibration, X-axis
- Results: Vibration, Y-axis
- Results: Vibration, Z-axis
- Results: Power draw (and motor power)
- Results: Cooling performance per watt, airflow
- Results: Cooling performance per watt, static pressure
- Airflow per euro
- Static pressure per euro
- Results: Lighting – LED luminance and power draw
- Results: LED to motor power draw ratio