Scythe Kaze Flex II 120 Slim: Well balanced SFF fan

Cooling, Extra tests, Fans | | Ľubomír Samák

Low-profile fans are a special category, but sometimes they are unavoidable in more confined spaces. For technical reasons, it’s always about compromises compared to more respectable fans of normal thickness, but their weight can vary. If the Arctic P12 Slim and Alphacool SL-15 don’t fit your needs, the Scythe Kaze Flex II 120 Slim may be the closest thing to what you’re looking for.

Results: Frequency response of sound with a dust filter

Measurements are performed in the TrueRTA application, which records sound in a range of 240 frequencies in the recorded range of 20–20,000 Hz. For the possibility of comparison across articles, we export the dominant frequency from the low (20–200 Hz), medium (201–2,000 Hz) and high (2,001–20,000 Hz) range to standard bar graphs.

However, for an even more detailed analysis of the sound expression, it is important to perceive the overall shape of the graph and the intensity of all frequencies/tones. If you don’t understand something in the graphs or tables below, you’ll find the answers to all your questions in this article. It explains how to read the measured data below correctly.

The sound of the 120 and 140 mm fans for the most part operates in the 70–700 Hz band. The bearings and motor operate between 1000 and 2500 Hz. Higher frequencies can be amplified by grilles or plastic filters (typically with hissing). Ignore the frequencies above 7000 Hz, these reflect electromagnetic noise from the measurement chain. This (electromagnetic noise) partially interferes with frequencies below 70 Hz as well, although there is still aerodynamic noise at these frequencies.

Note: For these measurements, a plastic filter is used, which, compared to a situation without an obstacle, bends the sound considerably more than a non-obstructive nylon filter.



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Wordpress Table Plugin

Why is there a missing value sometimes? There may be more reasons. Usually it is because the fan could not be adjusted to the target noise level. Some have a higher minimum speed (or the speed is low, but the motor is too noisy) or it is a slower fan that will not reach the higher decibels. But the results in the graphs are also missing if the rotor is brushing against the nylon filter mesh. In that case, we evaluate this combination as incompatible. And zero in the graphs is naturally also in situations where we measure 0.00. This is a common occurrence at extremely low speeds with obstructions or within vibration measurements.


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Comments (5) Add comment

  1. On the evaluation page, the link to frequency analysis on plastic filters was wrong (39 instead of 29). Also, the summary was wrongly replaced by the spec table.

    On your evaluation of frequency, you say thay the weakness of the fan only shows when it runs above 1100 RPM (that is 45 dBA). But from reading the charts, there seems to be strong peaks that appear in 39 dBA mode (959 RPM) as well. Did I interpret the data incorrectly?

    Reply

    1. Thank you for the heads up. Corrected. Including the charts that were really messed up. I was already in advanced stages of exhaustion when I released it yesterday…

      … you read the spectrographs well. Yes, you are right, even the 39 dBA (~959 rpm) mode is characterized by more pronounced tonal peaks, so I’ve modified that statement a bit. Below 850 rpm it’s fine in that respect. Approximately such speeds at 39 dBA correspond to tests with a plastic filter and on a grille, which increase the noise level, so when tuned to the same level the fan speeds will always be a bit slower than in a use case without an obstacle.

      So thanks for this observation and apologies for the inaccurate interpretation of the results. I wrote the article a bit under pressure and at the same time on the verge of complete exhaustion. I hope that similar mistakes will be avoided in the future.

      Reply

      1. You don’t have to apologize, it does not take away from the fact that the overall analysis is great work.

        Health is very important. I hope you’ll find time to take a good rest and don’t push yourself too hard 🙂. Take care.

        Reply

  2. Guys, please test 120 and 140x25mm Kaze Flex – they were highly praised by other (but not as advanced as you) reviewiers, especially as case fans. I generally really like them from my own experience for being solid performers; sounding well; having quiet motor and bearing and representing nice quality additionally proven by few years of using them in my own pc.

    Reply

    1. Sure, the 120 and 140 mm Kaze Flex II will be next in line as far as Scythe fans are concerned. I mean, maybe the Grand Tornado model, which is close to release, will fit in between them.

      Reply

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