Scythe Kotetsu CPU Cooler: A Compact King

Cooling
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STOCK FAN MEASUREMENTS

Specifications: Scythe Kotetsu Stock Fan
Manufacturer Scythe Power Rating 2.16 W
Model Number SY1225HB12SM-P Airflow Rating 20.7 ~ 79 CFM
Bearing Type Sleeve Speed Rating 400 (±200 rpm) ~ 1,400 rpm (±10%) (PWM-controlled)
Frame Size 120 x 120 x 25 mm Noise Rating 5.3 ~ 28 dBA
Hub Size 36 mm Header Type 4-pin PWM
Blade Diameter 113 mm Starting Voltage 3.5 ~ 4.0 V
Cable Length 30 cm Weight 120 g
Corner Type Open Retail Availability No
Additional notes:

The Kotetsu's stock fan is identical to that of the Mugen 4. This Glide Stream 1400 RPM PWM model is not sold to the public though there is a 1300 RPM variant available for sale. The fan's structure is similar to that of the Slip Stream series, with a small hub and struts curved in the opposite direction of the blades.

Stock Fan Measurements
Voltage
Speed
SPL@1m
12V
1410 RPM
29 dBA
9V
1130 RPM
22~23 dBA
7V
900 RPM
16 dBA
6V
790 RPM
14 dBA
5V
670 RPM
12 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

1400 RPM is well-suited for a CPU cooler, allowing for a versatile range in terms of noise. The fan was fairly loud at full speed (29 dBA@1m) but it quieted down dramatically as the speed was reduced, becoming quiet somewhere around 1000 RPM. Furthermore, at 800 RPM, it was almost inaudible, and at <700 RPM, it was practically silent. The SPL measurements were very close to the Mugen 4 sample with a variance of at most, 1 dB.


According to ASUS' Fan Xpert 2 utility, the included fan is controllable down to ~400 RPM and ~560 RPM via voltage and PWM control respectively.

As we've remarked in previous articles, the Glide Stream 120 has a pleasant sound. Its acoustic profile was mostly bereft of tonality, sounding smooth and innocuous. It whined somewhat at higher speeds, but this is typical of almost all sleeve bearing fans. Faint clicking was also observed at lower speeds but this was only audible at close distance.

TEST RESULTS

Test Results: Scythe Kotetsu (stock fan)
Fan Voltage
Fan Speed
SPL@1m
Thermal Rise
12V
1410 RPM
29 dBA
34°C
9V
1130 RPM
22~23 dBA
35°C
7V
900 RPM
16 dBA
38°C
6V
790 RPM
14 dBA
41°C
5V
670 RPM
12 dBA
42°C
Reference Nexus 120 mm Fan
12V
1080 RPM
17 dBA
37°C
9V
890 RPM
14 dBA
38°C
7V
720 RPM
11~12 dBA
41°C
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

The Kotetsu proved to be an excellent cooler, generating a thermal rise above ambient of 34°C at 12V --- this is a tremendous result at any noise level, even 29 dBA@1m. At the lowest tested fan voltage/speed, the result was only 8°C higher. The stock fan's performance was pretty good as well, though our reference Nexus fan had a 3°C advantage at 14 dBA.



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