be quiet! Shadow Rock Slim CPU Cooler

Cooling
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STOCK FAN MEASUREMENTS

Specifications: be quiet! Shadow Rock Slim Stock Fan
Manufacturer be quiet! Power Rating 4.8 W
Model Number BQ SIW3-13525-MR-PWM Airflow Rating 67.8 CFM
Bearing Type Rifle Speed Rating 1400 RPM
Frame Size 137 x 137 x 22 mm (120 mm holes) Noise Rating 23.7 dBA
Hub Size 46 mm Header Type 4-pin PWM
Blade Diameter 129 mm Starting Voltage 4.0 ~ 4.5 V
Cable Length 20 cm Weight 140 g
Corner Type Open Retail Availability No
Additional notes:

The Shadow Rock Slim stock fan is characterized by a large hub, blades ridged on both sides, and a wide angle between the slightly curved struts and the blades' trailing edges. On the exhaust side, the round frame has a soft/rubberized surface that presumably gives it some anti-vibration properties. The mounting holes are located on a second frame protruding outward at the center in an octagonal fashion.

Stock Fan Measurements
Voltage
Speed
SPL@1m
12V
1380 RPM
26 dBA
9V
1070 RPM
19 dBA
8V
960 RPM
16 dBA
7V
850 RPM
13~14 dBA
6V
730 RPM
12~13 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

As the stock fan has PWM capability, a low starting voltage, and a top speed of just 1400 RPM, the fan speed range available is quite good. At top speed we recorded a noise level of 26 dBA@1m which is low compared to most stock CPU fans. Dialing the speed back to 9V/1070 RPM was enough to make it quiet by our standards and it became almost inaudible at 6V/730 RPM. It can get even quieter as the starting voltage is well under 5V and we coaxed it down to a low of 380 RPM on PWM control.

The fan had interesting acoustics, producing mostly turbulent noise (the sound of rushing air) at top speed. At 9V, much of the turbulence dissipated, leaving behind a mildly annoying low frequency drone. At 8V, the droning suddenly vanished, as evinced by the disappearance of a ~320 Hz tonal spike in our acoustic analysis above. The resulting noise was much smoother, with a mostly broadband profile, and its prevalence continued at both 7V and 6V. Under 8V (about 1000 RPM), its acoustics were top-notch.

TEST RESULTS

Test Results: be quiet! Shadow Rock Slim
Fan Voltage
Stock Fan
Reference Fan
SPL@1m
Thermal Rise
SPL@1m
12V
26 dBA
37°C
38°C
29 dBA
9V
19 dBA
40°C
39°C
22 dBA
8V
16 dBA
41°C
41°C
19 dBA
7V
13~14 dBA
42°C
42°C
15 dBA
6V
12~13 dBA
44°C
44°C
13 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

The Shadow Rock Slim was an excellent cooler, generating a thermal rise above ambient of 44°C at 6V and 37°C at 12V. The stock fan performed almost identically to the Noctua NF-P14, producing the same results at 6V, 7V, and 8V, while only 1°C separated the two fans at 9V and 12V. However, the stock fan was quieter at every level, giving it the overall edge.



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