NZXT Kraken X31 & X41 Liquid CPU Coolers

Cooling
Viewing page 5 of 7 pages. Previous 1 2 3 4 5 6 7 Next

SOFTWARE

As there are dozens of similarly designed closed-loop water coolers on the market, NZXT has made an effort to differentiate their product with software. The USB cable links up to their CAM utility, giving users the ability to control fans plugged into the two provided headers while also monitoring CPU and GPU temperature, and CPU and memory usage. Fan speed can be regulated as well, either manually, or dynamically based on the temperature of the liquid rather than the CPU, but there is no option to adjust the pump speed.

NZXT claims the pump varies in speed automatically between 2400 and 3600 RPM based on thermal load, but during our time with it, their own software revealed it always ran close to the maximum speed regardless of the temperature. The pump can be slowed down but you have to do it yourself by connecting it to a voltage-controllable fan header and using alternate fan software. However, if you want to know the pump's rotational speed, that information is only available through their utility, which is unfortunate as both the fan and pump speeds it reported fluctuated by a sizable amount. For example, at full speed, using both a tachometer and SpeedFan, we determined the X31's fan to be spinning at a steady 1900 RPM, while CAM suggested it was continually ramping up and down within a range between 1700 and 2400 RPM. The amount of variation is surprising for something so simple.

The fan control options includes manual control between 40% and 100%, two predefined presets, and custom adjustment by tweaking the curve of the fan speed/temperature graph. The more advanced Kraken models (all those except the X31) are equipped with LED lighting on the base and the color can be changed here as well. Furthermore, if you sign up for an account, you can monitor the status of the cooler via the cloud and with an iOS and Android app scheduled to be released next month. We suppose that's the modern thing to do but who really needs to monitor or adjust their desktop cooling when away from home?

CAM need some serious polish but it's also not quite ambitious enough to replicate the full functionality of motherboard software. System and hard drive temperature sensors are no where to be found and fans connected to motherboard headers can't be monitored or controlled. So really, all CAM does is let you play with the LED color and monitor the pump speed. For many users, that's not worth having yet another annoying icon taking up space in the system tray.

STOCK FAN MEASUREMENTS

Specifications: NZXT Kraken X31 Stock Fan
Manufacturer NZXT Power Rating 2.4 W
Model Number RF-FX122-HP Airflow Rating 81.32 CFM (max.)
Bearing Type Hydro Dynamic Speed Rating 800 ~ 2000 RPM
Frame Size 120 x 120 x 25 mm Noise Rating 18 ~ 34 dBA
Hub Size 42 mm Header Type 4-pin PWM
Blade Diameter 114 mm Starting Voltage 4.0 ~ 4.5 V
Cable Length 40 cm Weight 140 g
Corner Type Closed Retail Availability No
Additional notes:

The X31's stock 120 mm fan uses a conservative design with seven large blades with a modest degree of curvature and sharp corners. The blades trail edges line up almost perfectly parallel with the straight struts, and while this typically is undesirable, the fan somehow manages to avoid producing any noticeable tonality. As with most fans paired with liquid coolers, it's a high speed model, rated for 2000 RPM at full tilt.


The stock fan's range according to Fan Xpert2. PWM control on the top, DC control on the bottom.

According to the specifications, the X31 stock fan has a lower limit of 800 RPM and this was more or less confirmed by ASUS Fan Xpert2. Whether it's on PWM or DC control, it can't be reliably run below about 800 RPM. This limits how quiet the cooler can be; it shouldn't matter because water coolers can't be that quiet in the first place due to ever-present pump noise.

Pump Measurements
12V
~3600 RPM
18~19 dBA
9V
~3200 RPM
16 dBA
7V
~2800 RPM
14 dBA
Stock Fan Measurements
Voltage
Speed
12V
1900 RPM
34 dBA
9V
1520 RPM
28 dBA
7V
1230 RPM
22~23 dBA
6V
1060 RPM
18 dBA
5V
900 RPM
14~15 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

At full speed the X31's pump generated 18~19 dBA which is about average for a closed loop liquid cooler, while 9V and 7V brought the SPL down to 16 and 14 [email protected] respectively. The fan has a much wider range, producing a very loud 34 [email protected] and full speed all the way down to a faint 14~15 [email protected] at 5V. To meet our standard of quiet, both the pump and the fan in particular, have be slowed down.

The noise profiles of the two components couldn't be more different. We were blown away by how the 120 mm stock fan sounded. It was exceptionally smooth with no detectable tonality or even a hint of bearing chatter when we held it up right next to our ears. Its superb character also remained consistent throughout its range. Simply put, it's best liquid bearing model we've ever encountered, and right up there with the gold-standard, the Nexus Real Silent case fan. As evidenced by the frequency analysis, it generated a much smoother broadband profile than the pump, which emits an annoyingly harsh buzz and rattle. The only good thing we can say about the pump is it doesn't make any weird gurgling noises like some water coolers we've reviewed in the past.

Specifications: NZXT Kraken X41 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 X41's fan appears to be a higher speed variant of their 1000 RPM FN V2. The rated speed is the same as the X31's stock fan, between 800 and 2000 RPM, but as it's a larger 140 mm model, it produces more airflow and noise. The design is completely different as well, similar to the 14~15 cm fans shipping with Thermalright's large coolers. With rounded leading blade tips, it resembles a torpedo propeller. The casing has been hollowed out near the corners, presumably to reduce weight, and each mounting hole is fitted with rubber pads to reduce vibration.


The stock fan's range according to Fan Xpert2. PWM control on the top, DC control on the bottom.

ASUS Fan Xpert2 revealed a similar effective range on PWM control as the X31's fan, but there was much more leeway under voltage control. This was confirmed by testing with a manual voltage controller which pegged its starting voltage at less than 4V.

Pump Measurements
12V
~3600 RPM
15 dBA
9V
~3200 RPM
13 dBA
Stock Fan Measurements
Voltage
Speed
12V
1960 RPM
43 dBA
9V
1510 RPM
35 dBA
7V
1200 RPM
28~29 dBA
6V
1020 RPM
23 dBA
5V
840 RPM
18 dBA
Measuring mic positioned 1m at diagonal angle from the center of the heatsink.
Ambient noise level: 10~11 dBA.

Surprisingly, despite the X31 and X41 being seemingly identical except for the size of the radiator and fan, the X41's pump was much quieter, so much so, that we didn't bother checking its noise level below 9V. We doubt the greater area of the larger radiator is responsible for such a discrephancy so we can only surmise that this is due to sample variation. The X41's fan on the otherhand is much louder than its smaller counterpart, as it is larger yet runs at the same speed. The noise is produced was earsplitting at full speed and we wouldn't personally use it at speeds greater than 1000 RPM.

The X41 fan was not quite as impressive as the X31. It sounded fairly smooth, though there was obviously quite a lot of turbulent noise at higher speeds. Its pitch was slightly higher and at the lowest tested speed of 840 RPM, it developed a mild clicking problem which is unfortunate as the fan needs to be slowed down by at least that much in order bring the noise down to a reasonably quiet level. The pump had similar acoustics to the X31, only the volume was greatly reduced. At full speed, it sounded like the X31 pump when undervolted.



Previous 1 2 3 4 5 6 7 Next

Cooling - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: