Scythe Grand Kama Cross CPU Cooler

Cooling
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TEST RESULTS

Stock Fan

Stock Fan Specifications
Manufacturer
Power Rating
2.64 W
Model Number
SM1425SL12LM-P
Airflow Rating
69.93 CFM
Bearing Type
Sleeve
RPM Rating
1300 RPM
Corners
Open
Noise Rating
24.7 dBA
Frame Size
120 x 120 x 25 mm
Header Type
4-pin PWM
Fan Blade Diameter
128 mm
Starting Voltage
~5.4 V
Hub Size
40 mm
Weight
140 g
Data in green cells provided by the manufacturer or observed; data in the blue cells were measured.

The 140 mm PWM Slip Stream is a 9-blade fan with a curved, but not quite round housing, 120 mm fan holes, and a surprisingly small hub.

Stock Fan Measurements
Voltage
Speed
SPL @1m
12V
1310 RPM
28 dBA
10V
1090 RPM
21 dBA
9V
970 RPM
17 dBA
8V
820 RPM
14 dBA
7V
680 RPM
11~12 dBA
Measuring mic positioned 1m at diagonal angle from the intake side of the fan.
Ambient noise level: 11 dBA.

The stock fan was previously tested when we reviewed the Prolimatech Armageddon, and the noise level was very similar with the exception of a 2 dBA increase at 12V which may have been caused by the metal frame to which the fan is mounted. Thankfully, this is not a serious issue since we consider both 26 dBA and 28 dBA too loud for serious consideration in a quiet PC.

The fan exhibits some minor bearing chatter, and is a little whiny at full speed, but other than that, its acoustics are excellent throughout its range like other members of the Slip Stream family. The fan is really only too loud at 12V. At 10V, the measured noise level is high at 21 dBA, but all you really hear is turbulence. It undervolts well, becoming inaudible at around 7V.


The Scythe 140 mm fan measured 17 dBA@1m at 9V. Frequency analysis revealed practically no tonality.

Cooling Results

Scythe Grand Kama Cross w/ stock 140 mm fan
Fan Voltage
SPL@1m
Temp
°C Rise
12V
28 dBA
59°C
38
10V
21 dBA
61°C
40
9V
17 dBA
62°C
41
8V
14 dBA
65°C
44
7V
11~12 dBA
70°C
49
Scythe Grand Kama Cross w/ ref. 120 mm fan
12V
16 dBA
66°C
45
9V
13 dBA
73°C
52
7V
12 dBA
78°C
57
Load Temp: Prime95 for ~10 mins.
°C Rise: Temperature rise above ambient (21°C) at load.

The Grand Kama Cross performed admirably considering that it is a top-down cooler. With the stock fan at fairly quiet 17 and 14 dBA levels, the thermal rise above ambient was only 41°C and 44°C, respectively. At 11-12 dBA the fan becomes almost inaudible, and the temperature increased by an additional 5°C. This would put the in-case temperature of the CPU at ~80°C or higher, which is probably too high for most users' comfort... but it may be a perfect acceptable setting if you know you will rarely push the CPU as hard was we do in our testing (100% load on all cores for >20 minutes continuously.)

Our Nexus 120 mm reference fan is apparently too small to be as effective as the stock 140mm fan, allowing the CPU to get 4°C hotter at 12V/16 dBA than the stock fan at 9V/17 dBA. As the reference fan's speed was slowed, the difference became more apparent. With both fans at 7V, the stock fan was slightly quieter and a very significant 8°C cooler. It's clear that the large stock fan is essential to the Grand Kama Cross' success.



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