Thermalright Ultra-120 eXtreme Rev.C & AC Freezer Xtreme Rev.2

Cooling
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Stock Fan Measurements

We begin with an analysis of the stock fan, in this case a mysterious proprietary 120 mm model with a circular frame attached to a pair of release tabs.

Specifications: AC Freezer Xtreme Rev.2 Stock Fan
Manufacturer
Power Rating
1.8 W
Model Number
?
Airflow Rating
35.7 CFM
Bearing Type
?
Speed Rating
1500 RPM
Corners
N/A
Noise Rating
0.5 sone
Frame Size
126 x 124 x 30 mm (excluding release mechanism)
Header Type
4-pin PWM
Fan Blade Diameter
110 mm
Starting Voltage
3.8 V
Hub Size
48 mm
Weight
140 g
Data in green cells provided by the manufacturer or observed; data in the blue cells were measured.

The stock fan has seven swept-forward blades with sharp edges. Its wingspan is a bit short and the hub overly large compared to the average 120 mm case fan with a box frame.

Stock Fan Measurements
Voltage
Speed
SPL @1m
12V
1430 RPM
27 dBA
9V
1180 RPM
22 dBA
7V
980 RPM
17 dBA
5V
790 RPM
12~13 dBA
Measuring mic positioned 1m at diagonal angle from the intake side of the fan.
Ambient noise level: 10~11 dBA.

We would characterize the overall noise character of the fan to be smooth. It has a tendency to drone at high speeds, and produces turbulent noise at 7V and above, but generally it sounds quite benign, lacking any annoying tones. The acoustic quality is excellent as are many of Arctic Cooling's fans. The fan on our sample ran 1430 RPM at 12V, producing a fairly loud 27 dBA@1m in our anechoic chamber. At 5V, 790 RPM, it was almost inaudible at 12~13 dBA@1m.


The Freezer Xtreme's stock fan becomes quiet at about 7V.

COOLING RESULTS

Fan Voltage
SPL@1m
°C Rise
Freezer Xtreme Rev.2
Ultra-120 eXtreme Rev.C
Stock 120mm Fan
12V
27 dBA
48
N/A
9V
22 dBA
51
N/A
7V
17 dBA
55
N/A
5V
12~13 dBA
62
N/A
Reference 120mm fan
12V
16 dBA
49
38
9V
13 dBA
52
40
7V
12 dBA
58
43
2 x Reference 120mm fans
12V
19 dBA
44
36
9V
14 dBA
45
38
7V
12 dBA
48
40
°C Rise: Temperature rise above ambient (22°C) at load.

The Freezer Xtreme's stock fan was excellent acoustically, but its cooling ability was very poor compared to our reference Nexus fan, which we inserted into the fan slot without any support (you can suspend it with wire, zip-ties or the like). The Nexus beat the stock fan by 4~10°C at the 12~13 dBA level and by 6°C at 16~17 dBA. We can think of two possible causes for this performance difference. The fan blades are smaller than a typical 120 mm fan because the large hub takes up extra space and there is a large gap between the blades and the housing. This separation probably produces less pressure as well.

Even with our reference fan, the Freezer Xtreme was beaten soundly by the Ultra-120 eXtreme to the tune of 11~15°C depending on the fan speed. With a second reference fan employed at the front of the heatsink, its performance was boosted by 7~10°C, with the best improvement being made at the very quiet 7V level. A second fan on the Ultra-120 eXtreme only produced a 2~3°C benefit.


A second fan at the front of the Freezer Xtreme interfered with the RAM.

A second fan is very beneficial to the Freezer, but because the fin stack sits so low, it interfered with the system memory installed on our test board when we positioned it as an intake. As a result we had to rest the fan on one of the DIMMs, so it ended up being higher than the center fan. Putting the fan on the opposite side isn't ideal as separation would need to be created so that the hub would not scrap against the surface of the heatsink (there are no struts on the back side of the fan to keep them apart). A fan at the back would be closer to the exhaust fan in most systems, but with a constricted intake, it would probably generate more noise.


The AC Freezer Xtreme's thermal compound footprint.

The Freezer's slightly concave base creates a contact problem. Excess thermal compound is squeezed out to the edges of the base when good firm contact is made, but as you can see from the image above much of it remained at the center where the CPU is hottest. The Ultra-120 eXtreme by comparison has a convex base (both the Rev.C and original version) to maximize contact with the center of the CPU heatspreader and mounting leaves most of the residue on the outside of the base.



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