NZXT Kraken X61 28cm Liquid Cooler

Cooling
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SOFTWARE

There are many similar closed-loop all-in-one water coolers on the market. NZXT's CAM software utility helps them differentiate their cooler.


Main interface (advanced).

The software provides monitoring of the CPU/ GPU temperature, fan speeds (only those fans connected directly to the cooler), and CPU/GPU usage. Unfortunately, It doesn't have access to any additional sensor data from the hard drive and motherboard so it complements rather than replaces utilities like the ASUS AI Suite, Gigabyte's EasyTune, and SpeedFan.

CAM was problematic on both the X31 and X41, as the reported fan and pump speed varied from second to second by a considerable degree, and the pump speed couldn't be adjusted at all. Our X61 sample was much better in this regard — the reported fan speed was steady and accurate (though not the pump speed), and the control slider adjusted both the fan and pump speeds in unison. Control is available in the form of a constant manual setting and a dynamic option that allows users to either customize the fan speed/temperature curve to their liking, or to select between two presets.

The minimum manual setting resulted in a fan speed of about 1100 RPM which was fairly loud, easily drowning out the noise emitted by the pump motor which ran at ~2900 RPM. We also felt the maximum pump speed of ~3700 RPM was too high. A cursory check found identical performance whether the pump was running at maximum or minimum speed. If you truly want a quiet experience with this product, the included software doesn't quite provide it. You'll see below what we had to do to achieve quiet cooling.


LED lighting options.

A secondary function of CAM is to adjust the cooler's lighting effects using several different modes. "Standard" sets a single constant color, "Breathing" alternates between two colors at a moderate rate, "Blinking" does the same only at a faster rate, and "Rainbow" breathes through all seven major rainbow band colors (red, orange, yellow, green, blue, indigo, and violet). A different warning color can also be selected to indicate if the CPU heats up above a specified temperature. As for the available colors themselves, you can choose any RGB combination so if you prefer it to be as subtle as possible you can make it white or black.

STOCK FAN MEASUREMENTS

Specifications: NZXT Kraken X61 Stock Fan
Manufacturer NZXT Power Rating 7.2 W
Model Number RF-FX142-NP Airflow Rating 42.4 ~ 106.1 CFM
Bearing Type Nano Speed Rating 800 ~ 2000 RPM
Frame Size 140 x 140 x 25 mm Noise Rating 20 ~ 37 dBA
Hub Size 42 mm Header Type 4-pin PWM
Blade Diameter 132 mm Starting Voltage 4.0 V
Cable Length 40 cm Weight 180 g
Corner Type Closed Retail Availability No
Additional notes:

The stock fan included is the same as the X41, a high speed PWM variant of their 1000 RPM FN V2. The fin and strut shape is similar to the 14~15 cm fans that ship with Thermalright's larger coolers. The prominent rounded leading blade tips makes it look like a torpedo propeller. Interestingly, the casing is hollowed out around the corners, reducing the overall weight and allowing the fan cable to routed around the edge without sticking out. Each mounting hole is outfitted with dampening pads to limit vibration.


The stock fan's PWM range according to Fan Xpert2.

According to ASUS' Fan Xpert2 utility, its effective PWM control range bottoms out at just 860 RPM. This is lower than what CAM allows, but is still a bit high for a 14 cm model. As the X61 has two fans, maintaining a low overall noise level with PWM control alone isn't possible.

Stock Fan Measurements (dual fans)
Voltage
Avg. Speed
12V
1940 RPM
45 dBA
9V
1450 RPM
36~37 dBA
7V
1120 RPM
29 dBA
6V
960 RPM
24~25 dBA
5V
750 RPM
18 dBA
4V
590 RPM
15 dBA
Pump Measurements (min. speed in CAM)
12V
~2900 RPM
19 dBA
9V
~2500 RPM
16 dBA
7V
~2200 RPM
14 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

On voltage control, we found the starting voltage was exactly 4.0 V for both fan samples, which was good for just under 600 RPM, much lower than with PWM control. DC control is the way to go if you want to achieve something resembling silence with the stock fans. Even with this lower minimum speed, the noise produced by the pair (15 [email protected]) wasn't quite as low as we would like, and at ~1000 RPM and above, it was loud by our standards. The top speed generated a SPL of 45 [email protected], one of the highest we've measured for a CPU cooler.

The CAM software is useful for one thing: Setting the pump to its minimum speed of ~2900 RPM. This, in conjuction with manual motherboard voltage control, allowed us to lower the pump speed further. The pump had a modest noise impact at 2900 RPM compared to the fans but we'll try anything if it can potentially lower the overall noise.

Adding a second identical fan not only increases the noise level, it can also potentially amplify any unpleasant characteristics in its noise signature. Thankfully, the stock fan is one of the best sounding 14 cm models we've used. Both samples' acoustics were slightly superior to the fan that shipped with the X41. Though very turbulent at high speed, they had a mostly smooth profile throughout most of the range. At lower speeds they clicked a bit but this was only noticeable close up and faded away with distance.

The pump didn't have a nice sound but it's a significant improvement over most other pumps. It had a bothersome growl at ~2900 RPM but this went away at lower speeds, though there was buzzing and rattling at all speeds. When the pump and fans speeds were adjusted to produce approximately the same noise level, the fans were silky smooth by comparison and had a more pleasant lower pitch.

The pump and fans sound different enough that neither really canceled out or masked the other when operating simultaneously. The buzzing of the motor and the "whoosh" of the fans were clearly audible and distinct from one another. Notably, the pump's tonal peaks (particularly at 2 KHz and above) remained.



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