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NZXT Kraken X61 28cm Liquid Cooler

With a massive 28 cm radiator, dual 14 cm fans, lighting effects, and software to control pump and fan speeds, the NZXT Kraken X61 has the makings of a truly premier CPU cooling solution. Our review shows you how to run it super quietly while achieving great cooling.

September 20, 2014 by Lawrence Lee

Product
NZXT Kraken X61
AIO Liquid CPU Cooler
Manufacturer
NZXT
Street Price
US$140

While many PC enthusiasts have deemed closed-loop liquid cooling solutions
to be the defacto standard for premium builds, we at SPCR are far from convinced.
It’s a neat idea use forced flowing liquid for heat extraction, but thus far
most water cooling units we’ve reviewed have underperformed. We haven’t tested
that many but it’s still telling that in the past four years, we’ve recommended
only one: The NZXT Kraken X41 — and that was just last month.

Both the Kraken X31 and X41
are notable for having an excellent base, a reasonably quiet pump, and a superb-sounding
stock fan. The X31 proved to be an average performer, but the X41 was miles
ahead, putting it into contention against some of the very best tower heatsinks.
As the two coolers’ base/pump mechanism are essentially the same, the difference
came down to the X41’s larger 14 cm radiator and fan. Size, or rather surface
area, turned out to be the key factor. The X61 we’re examining today is even
bigger, so hopes are high that it can do some serious cooling damage. Nothing
less is acceptable considering its US$140 price, which some people wouldn’t
pay even for a processor, let along a cooling solution.


The X61 box.

NZXT Kraken X61: Specifications
(from the product
web page
)
Model Number RL-KRX61-01
CPU Compatibility Intel LGA 2011-3, 1366, 1156, 1155, 1150
AMD FM2, FM1, AM3+, AM3, AM2+, AM2
Material Copper
Aluminum
Rubber
Plastic
Dimensions 40 (W) x 280 (H) x 27mm (D)
Tube Length 400mm
LED Color Hue Controlled Color Changing Lights
Control Method Kraken+ Software Module
Warranty 6 Years
Motor
Speed 2400-3600 ± 150 RPM
Voltage 12V DC
Current 325mA
Connector 3-Pin
Fan
Model NZXT FX V2 140mm Performance PWM Fan
Dimensions 140 x 140 x 25mm
Speed 800~2000 RPM ± 10%
Air Flow 42.4-106.1 CFM
Air Pressure 0.36-1.97 mmH20
Bearing Nano
Voltage 12V DC
Connector 4-Pin PWM

The X61 is essentially a dual X41, with the radiator enlarged to fit two 14
cm fans instead of one (though it is thinner). The smaller 12/14 cm units can
be installed in just about any fan placement in a case, but the larger X61 radiator
is best mounted on the top panel, though front or bottom positioning is possible
if the case size and layout is suitable. The rest of the unit is the same as
the X31/X41 as far as we can tell, with an identically sized pump/base structure
and the same length/thickness of tubing. The pump runs 3600 RPM at top speed,
as with the other Krakens, and two of the X41’s pleasant 14 cm stock fans are
included. Once again, there are adjustable lighting effects on the base and
a software utility to control and monitor everything. We didn’t get pump speed
control working with our previous Kraken samples but hopefully the X61 doesn’t
suffer from this issue.


Packaging.


Contents.

The X61 uses packaging similar to other closed-loop water cooler on the market.
The cooler is spread out in a paper carton inside the outer box with the fans
and accessories segregated in a small compartment at the center. The X61 ships
with the cooler itself, a pair of 14 cm fans, an assembly guide, and the necessary
mounting hardware including a plastic backplate and AMD mounting frame (the
Intel frame is attached by default). The usual tube of thermal compound is absent
as it is pre-applied, and there’s no fan adapter as all the necessary connectors
are wired direclty to the base.

PHYSICAL DETAILS

The X61 is constructed in a similar fashion to most AIO liquid
cooling units. The base is comprised of a round plastic structure housing a
pump and reservoir inside and a thin copper coldplate at the bottom to draw
heat off the CPU. Liquid coolant carries the heat through 40 cm of tubing to
a large radiator with tightly wound aluminum coils and is expelled via a pair
of 14 cm fans. The radiator measures 31.1 x 13.9 x 2.6 cm by our measurements.


The heat exchanger is thinner than both the X31 and X41 but as it is spread out over an additional fan position, it has substantially greater surface area. The unit has 14 cm mounting holes only, so both the fan placements it’s mounted to, and the fans themselves, must have the same.


The radiator coils are just 0.13 mm thick and spaced 1.02 mm apart from one another on average. It’s the most densely packed cooler we’ve ever encountered. The rubber tubing is 10.6 mm in diameter, the same as the X31/X41.


The base is identical in size to the X31/X41, 3.0 cm tall with a 5.5 cm
diameter base plate. It shares the same LED feature with the X41, with
the NZXT logo on top lighting up in a wide spectrum in colors. The Intel
mounting frame is installed out-of-the-box which is appropriate for this
particular model given its price.


A myriad of connectors emanate from the base. There’s a 20 cm 3-pin connector for the pump, a 30 cm line of daisy-chained 4-pin PWM connectors to power/control up to four fans (only one has an RPM sensor), a SATA plug to power the aforementioned fans, and a 60 cm USB 2.0 connector required for NZXT’s software.


A thin layer of thermal compound is pre-applied to the base for convenience.


A quick look at the reflection off the baseplate surface shows it has
a slightly convex shape with a center pinpoint marking the apex. Faint
circular machine marks are visible with a prominent line about halfway
from the edge.

INSTALLATION

The most critical aspect of installation is firm, maximum contact
between the base and the CPU heatspreader for efficient heat conduction. Ideally
it should also be a simple procedure with the user having to handle as few pieces
of hardware as possible. The X61’s mounting system is not as heavy duty as other
schemes but it’s sufficiently stiff and simple to put together.


The X61’s mounting gear. A plastic backplate is utilized, perhaps because
the base of the cooler is not very heavy. Double-sided standoffs are used
to secure the backplate to the motherboard and thumbnuts pin down the
mounting frame. Fans are mounted using long bolts and washers, and short
screws keep the radiator in place.


Before installing, it would be prudent to quickly check the mounting hardware.
Our sample included a thumbnut that was only partially threaded, preventing
it from properly mating with the standoffs. We had to borrow a nut from
our X31/X41 samples to get the X61 installed.


Backplate and standoffs installed.


Fully mounted and plugged in.


Obviously the lighting is more impressive in a dark environment.


We mount our CPU coolers on a Puget Systems Test Bench but as it lacks
as a dual 14 cm fan mount, we placed the radiator on the X61 box with
a bed of foam along the top side of the motherboard to simulate its typical
position inside a case.

TESTING

Before thermal testing, we took some basic physical measurements of the radiator for comparison.

Large Heatsink Comparison:
Average Fin Thickness & Spacing
Heatsink
Fin Thickness
Fin Spacing
SilverStone Heligon HE02
0.52 mm
3.30 mm
Thermalright HR-01 Plus
0.45 mm
3.15 mm
Thermalright HR-02 Macho
0.34 mm
3.12 mm
Thermalright HR-22
0.53 mm
2.74 mm
Scythe Ninja 3
0.39 mm
2.64 mm
Noctua NH-U12P
0.44 mm
2.63 mm
Noctua NH-C12P
0.47 mm
2.54 mm
LEPA LV12
0.51 mm
2.38 mm
Noctua NH-D14
0.43 mm
2.33 mm
Thermalright Archon SB-E
0.49 mm
2.33 mm
GELID Tranquillo Rev.2
0.40 mm
2.30 mm
Phanteks PH-TC12DX
0.39 mm
2.30 mm
GELID GX-7 Rev.2
0.31 mm
2.25 mm
Phanteks PH-TC14PE
0.40 mm
2.21 mm
be quiet! Dark Rock 2
0.38 mm
2.22 mm
Prolimatech Armageddon
0.51 mm
2.08 mm
Prolimatech Megahalems
0.50 mm
2.00 mm
Zalman CNPS10X Quiet
0.40 mm
2.00 mm
Scythe Ashura
0.43 mm
1.97 mm
NZXT Havik 140
0.41 mm
1.91 mm
Scythe Mugen-2
0.31 mm
1.89 mm
SilverStone Tundra TD03 (radiator)
0.43 mm
1.86 mm
SilverStone Argon AR01
0.30 mm
1.85 mm
Thermalright Venomous X
0.53 mm
1.84 mm
Scythe Mugen 4
0.30 mm
1.82 mm
Noctua NH-D15
0.46 mm
1.79 mm
Noctua NH-C14
0.38 mm
1.79 mm
Enermax ETS-T40
0.40 mm
1.79 mm
Scythe Yasya
0.32 mm
1.78 mm
Enermax Liqtech 120X (radiator)
0.46 mm
1.76 mm
be quiet! Shadow Rock Slim
0.42 mm
1.73 mm
SilverStone Argon AR03
0.42 mm
1.72 mm
Noctua NH-U14S
0.42 mm
1.72 mm
Cogage TRUE Spirit 1366
0.40 mm
1.70 mm
Scythe Kotetsu
0.35 mm
1.66 mm
Scythe Grand Kama Cross
0.38 mm
1.66 mm
Zalman CNPS9900 MAX
0.16 mm
1.59 mm
Thermalright Silver Arrow
0.32 mm
1.57 mm
Cooler Master Hyper 212 Plus
0.43 mm
1.54 mm
Thermalright Ultra-120 eXtreme Rev.C
0.56 mm
1.52 mm
NZXT Kraken X31/X41 (radiator)
0.15 mm
1.07 mm
NZXT Kraken X61 (radiator)
0.13 mm
1.02 mm

Testing on larger heatsinks like this one is done on our
LGA1366 heatsink testing platform
. A summary of the test system and
procedure follows.

Key Components in LGA1366 Heatsink Test Platform:

  • Intel Core i7-965 Extreme
    Nehalem core, LGA1366, 3.2GHz, 45nm, 130W TDP.
  • Asus
    P6X58D Premium
    ATX motherboard. X58 chipset.
  • Asus
    EAH3450 Silent
    graphics card.
  • Intel
    X25-M
    80GB 2.5″ solid-state drive. Chosen for silence.
  • 3GB QiMonda
    DDR3 memory. 3 x 1GB DDR3-1066 in triple channel.
  • Seasonic X-650 SS-650KM
    650W ATX power supply. This PSU is semi-passively cooled. At the power levels
    of our test platform, its fan does not spin.
  • Arctic Silver
    Lumière
    : Special fast-curing thermal interface material, designed
    specifically for test labs.
  • Noctua 140 mm fan (used when possible with heatsinks that fit 140x25mm
    fans)
  • Nexus 120 mm fan (used when possible with heatsinks that fit 120x25mm
    fans)
  • Nexus 92 mm fan (used when possible with heatsinks that fit 92x25mm
    fans)

The systems are silent under the test conditions, except for the CPU cooling
fan(s).

Normally, our reference fans are used whenever possible, the measured details
of which are shown below.

Reference Noctua 140mm fan
Anechoic chamber measurements
Voltage
Speed
SPL@1m
12V
1250 RPM
28~29 dBA
9V
990 RPM
21 dBA
8V
880 RPM
18 dBA
7V
770 RPM
15~16 dBA
6V
660 RPM
13 dBA

 

Reference Nexus 120 mm fan
Anechoic chamber measurements
Voltage
Speed
SPL@1m
12V
1080 RPM
16 dBA
9V
880 RPM
13 dBA
7V
720 RPM
12 dBA

 

Reference Nexus 92 mm fan
Anechoic chamber measurements
Voltage
Speed
SPL@1m
12V
1470 RPM
17 dBA
9V
1280 RPM
14 dBA
7V
1010 RPM
12 dBA

Measurement and Analysis Tools

  • Extech 380803 AC power analyzer / data logger for measuring AC system
    power.
  • Custom-built, four-channel variable DC power supply, used to regulate
    the fan speed during the test.
  • PC-based spectrum analyzer:
    SpectraPlus with ACO Pacific mic and M-Audio digital
    audio interfaces.
  • Anechoic chamber
    with ambient level of 11 dBA or lower
  • Various other tools for testing fans, as documented in our
    standard fan testing methodology
    .
  • SpeedFan,
    used to monitor the on-chip thermal sensors. The sensors are not calibrated,
    so results are not universally applicable. The hottest core reading is used.
  • Prime95,
    used to stress the CPU heavily, generating more heat than most real applications.
    All instances are used to ensure full stress.
  • CPU-Z,used to monitor the CPU speed to determine when overheating occurs.
  • Thermometers to measure the air temperature around the test platform
    and near the intake of the heatsink fan.

Noise measurements are made with the fans powered from the lab’s variable DC
power supply while the rest of the system is off to ensure that system noise
do not skew the measurements.

Load testing was accomplished using Prime95 to stress the processor, and the
graph function in SpeedFan was used to ensure that the load temperature is stable
for at least ten minutes. The temperature recorded is the highest single core
reading. The stock fans were tested at various voltages to represent a good
cross-section of airflow and noise performance.

The ambient conditions during testing were 10~11 dBA and 21~23°C.

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
SPL@1m
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 dBA@1m) 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
dBA@1m, 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.

TEST RESULTS

The presence of a pump forces us to adjust our testing methodology in order to achieve maximum cooling potential. Tests were conducted by varying voltages for both the pump and fan. Some levels were not tested if the fan was obviously going to drown out the pump (or vice versa) by a big margin.

Test Results: NZXT Kraken X61 (Dual Stock Fans)
Pump Voltage / Speed
Fan Voltage / Speed
Thermal Rise
SPL@1m
12V / ~2900 RPM
(19 dBA)
12V / 1940 RPM
28°C
45 dBA
9V / 1450 RPM
29°C
36~37 dBA
7V / 1120 RPM
31°C
29 dBA
6V / 960 RPM
31°C
25 dBA
5V / 750 RPM
33°C
21 dBA
4V / 590 RPM
35°C
19 dBA
9V / ~2500 RPM
(16 dBA)
5V / 750 RPM
34°C
20 dBA
4V / 590 RPM
37°C
17 dBA
7V / ~2200 RPM
(14 dBA)
5V / 750 RPM
36°C
20 dBA
4V / 590 RPM
38°C
16~17 dBA
Dual Reference 140 mm Fan (Noctua NF-P14)
12V / ~2900 RPM
(19 dBA)
12V / 1250 RPM
33°C
34 dBA
9V / 990 RPM
34°C
28 dBA
7V / 770 RPM
36°C
22 dBA
6V / 660 RPM
37°C
20 dBA
9V / ~2500 RPM
(16 dBA)
7V / 770 RPM
36°C
21~22 dBA
6V / 660 RPM
37°C
18 dBA
7V / ~2200 RPM
(14 dBA)
7V / 770 RPM
36°C
20~21 dBA
6V / 660 RPM
38°C
17~18 dBA
Best 20 dBA and lower result for each sample/fan configuration in bold.
Measuring mic positioned 1m at diagonal angle from
the center of the heatsink.
Ambient noise level: 10~11 dBA.

The Kraken X61 was a tremendous performer with thermal rise results in the
low to mid 30’s. It becomes just the second CPU cooler to break the 30°C
rise mark (the first being its little brother, the X41) though very high fan
speed (and noise) was required to accomplish this feat. Still, its cooling proficiency
didn’t drop much as fan speeds were decreased. Lowering the pump speed to ~2500
RPM had a small effect on temperatures but it was necessary in order to achieve
a noise level below 19 dBA@1m. A similar outcome was observed at ~2200 RPM.

Our reference Noctua fans fared moderately worse than the stock fans, but they held up better when the pump was slowed.

HEATSINK COMPARISON TABLES

°C Rise Comparison: CPU Coolers with Dual Fans
SPL (dBA@1m)
22
21
20
19
18
17
16
15
14
13
12
11
NZXT Kraken X61
33
34
35
37
Prolimatech Genesis*
(reference fans)
35
36
37
39
Thermalright Silver Arrow
35
38
40
Noctua NH-C14
36
37
39
41
NZXT Kraken X61
(reference fans)
36
38
Thermalright HR-22*
(reference fans)
37
38
39
Noctua NH-D15
38
39
40
Thermalright HR-02 Macho*
(reference fans)
36
37
40
Noctua NH-U14S*
(reference fans)
39
40
Phanteks PH-TC14PE
38
39
41
 
Scythe Mugen 4*
(reference fans)
39
40
42
NZXT Havik 140
39
41
Scythe Ashura*
(reference fans)
40
 
41
43
Phanteks PH-TC12DX
41
 
44
Cooler Master Seidon 240M
40
43
53
SilverStone Tundra TD03
40
SilverStone Heligon HE02*
(reference fans)
44
 
46
Enermax Liqtech 120X
44
45
Zalman CNPS9900DF
48
 
50
53
 
SPL (dBA@1m)
22
21
20
19
18
17
16
15
14
13
12
11
Liquid coolers in blue.
*Models lacking dual stock fans tested with dual reference Noctua NF-P14 fans.

Compared to previous coolers we’ve tested with dual fans, the X61 takes the
top spot, just squeaking by the Prolimatech
Genesis
for the title. When paired with our reference fans, it drops
a few rungs but it’s still within a degree or decibel of the very best. [Editor’s
Note:
Insignificant in actual use and likely within the test margin of error.
]
Against other liquid coolers, well there’s simply no competition. The Seidon
240M
, Tundra TD03,
and Liqtech 120X are’t
even in the same league.

°C Rise Comparison: CPU Coolers with Single/Dual Stock Fan(s)
SPL (dBA@1m)
22
21
20
19
18
17
16
15
14
13
12
11
NZXT Kraken X61
33
34
35
37
Prolimatech Genesis*
(reference fans)
35
36
37
39
Thermalright Silver Arrow
35
38
40
Noctua NH-C14
36
37
39
41
Scythe Kotetsu
35
38
41
42
NZXT Kraken X61
(reference fans)
36
38
Thermalright HR-22*
(reference fans)
37
38
39
Noctua NH-D15
38
39
40
Thermalright Archon SB-E
39
40
43
Phanteks PH-TC14PE
38
39
41
Thermalright HR-02 Macho
38
39
40
41
43
Scythe Mugen 4
40
42
45
Noctua NH-U14S
38
40
43
NZXT Kraken X41
38
NZXT Havik 140
39
41
be quiet! Shadow Rock Slim
40
41
42
Scythe Yasya
40
43
Cogage TRUE Spirit 1366
41
43
46
Zalman CNPS10X Quiet
40
42
47
Scythe Grand Kama Cross
40
41
44
49
Scythe Ashura
42
44
Cooler Master Hyper 212 Plus
41
44
54
Phanteks PH-TC12DX
41
 
44
Silverstone Argon AR03
41
43
48
Scythe Ninja 3
44
46
SilverStone Argon AR01
42
44
50
Titan Fenrir
43
45
47
Cooler Master Seidon 240M
40
43
53
SilverStone Tundra TD03
40
SilverStone Heligon HE02*
(reference fans)
44
 
46
Antec Kühler H20 620
42
44
47
LEPA LV12
45
48
52
Zalman CNPS9900 MAX
45
47
49
NZXT Kraken X31
43
44
47
Enermax Liqtech 120X
44
45
GELID Tranquillo Rev.2
48
49
50
be quiet! Dark Rock 2
48
52
55
61
Zalman CNPS9900DF
48
50
53
GELID GX-7 Rev.2
49
51
56
Core i7-980X Stock Cooler
53
62
Enermax ETS-T40
49
55
64
Core i7-920 Stock Cooler
64
FAIL
SPL (dBA@1m)
22
21
20
19
18
17
16
15
14
13
12
11
Single/Dual fan air-cooled heatsinks in light/dark green.
Single/dual fan liquid coolers in light/dark blue.
*Fanless models tested with dual reference Noctua NF-P14 fans.

Naturally, the X61 retains its position when we include single fan heatsinks but many of the top coolers start to look inefficient. Not far behind the leader is the much smaller and cheaper Scythe Kotetsu.

MP3 SOUND RECORDINGS

These recordings were made with a high
resolution, lab quality, digital recording system
inside SPCR’s
own 11 dBA ambient anechoic chamber
, then converted to LAME 128kbps
encoded MP3s. We’ve listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

The recording starts with 5 second segments of room ambiance, then the fan
at various levels. For the most realistic results, set the volume so that
the starting ambient level is just barely audible, then don’t change the volume
setting again.

  • NZXT Kraken X61 stock fans only at 1m
    — 4V/590 RPM (15 dBA@1m)
    — 5V/750 RPM (18 dBA@1m)
    — 6V/960 RPM (24~25 dBA@1m)
    — 7V/1120 RPM (29 dBA@1m)
    — 9V/1450 RPM (36~37 dBA@1m)
    — 12V/1940 RPM (45 dBA@1m)
  • NZXT Kraken X61 at 1m
    — pump at ~2500 RPM, fans at 4V/590 RPM (17 dBA@1m)
    — pump at ~2500 RPM, fans at 5V/750 RPM (20 dBA@1m)
    — pump at ~2900 RPM, fans at 4V/590 RPM (19 dBA@1m)
    — pump at ~2900 RPM, fans at 5V/750 RPM (21 dBA@1m)
    — pump at ~2900 RPM, fans at 6V/960 RPM (25 dBA@1m)

FINAL THOUGHTS

With the promising results of the NZXT
Kraken X41
, we were optimistic about the larger X61’s chances. Frankly,
this is the sort of performance we’ve been awaiting since AIO liquid coolers
debuted. After repeated disappointments, the X61 is the first to truly impress
us, doing so in stunning fashion. Not only did it shoot past all the closed-loop
water coolers we’ve tested so far, it climbed to the very top of our leaderboard.
Even so, we need to note that if you want a truly silent cooling system,
the X61 is not it. We were able to get the SPL down to 16~17 dBA, but no better.
This is very quiet by any standard but not truly silent. In contrast, the top
air-only coolers on our leaderboard can go all the way down to the 11 dBA ambient
level of our anechoic chamber, albeit with higher temperature rise.

The key to the X61’s success is threefold. Time and time again, we’ve found
the base shape to absolutely vital to performance. The entire Kraken series
uses a slighltly convex base surface that enables superior contact with the
CPU heatspreader. Size is the second factor. The X31 is nothing special, the
larger X41 is good, and the even bigger X61 is excellent. Doubling the radiator’s
surface area makes the fans’ job much easier than using a thicker compact and
push-pull dual fans. Finally, the noise emitted is superb compared to other
liquid coolers. The stock fans are the best sounding 14 cm models we’ve had
the pleasure of listening to in some time and they deliver good cooling performance
to boot. The pump has an unpleasant sound (as do all pumps we’ve heard) but
at least the overall noise level is modest.

Our chief complaint is that achieving the low noise operation documented here
requires a fair amount of creativity and experimentation. Following NZXT’s standard
instructions will provide superb cooling performance but not with low noise
(as we define it). Both the fans and pump have very high top speeds, and the
included software can’t reduce it as much as is needed. Used as intended —
i.e. connect the fans via the included SATA-powered fan headers, and set the
software’s speed controls to minimum — the X61 generates 29 dBA@1m SPL,
which is most definitely not quiet. You need other means to slow the fans and
the pump down, like a third party controller or the headers on your motherboard,
but it’s a waste to have all those unused connectors dangling off the base.

The price is another hurdle. You have to plunk down a hefty US$140 for
the X61’s exceptional performance, putting it out of reach for all but the most
extreme enthusiasts. It’s a shame that the first closed-loop water cooler we
can wholeheartedly recommend is so expensive. It offers value only if you ignore
all the smaller air-only heatsinks that can deliver 90~95% of the cooling at
a fraction of the cost. Still, if you’re dead-set on quietly cooling a red hot
CPU in a big system and have the cash to spend, then you can’t go wrong with
the X61.

Our thanks to NZXT
for the Kraken X61 liquid CPU cooler sample.


The NZXT Kraken X61 is Recommended by SPCR.

* * *

SPCR Articles of Related Interest:

Recommended Heatsinks
Enermax Liqtech 120X AIO Liquid CPU Cooler
Sub-$20 CPU Coolers: A Reader’s Roundup
LEPA LV12 Direct-Touch Heatsink
NZXT Kraken X31 & X41 Liquid CPU Coolers
Noctua NH-D15: Update to an Icon

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