Antec KÜHLER H₂O 650 – Test and Review

Before I start with the article and later do the tests I believe I should say a few words about all of the new models recently added in the Antec KÜHLER H₂O series:

  1. Antec KÜHLER H₂O 650 – high-performance liquid cooling featuring a single slot slim radiator cooled by one 120mm fan PWM powered and regulated. The water flow is guaranteed by a single water pump.
  2. Antec KÜHLER H₂O 950 – high-performance liquid cooling featuring a single slot thick radiator cooled by two 120mm fans PWM powered and regulated. The water flow is guaranteed by a single water pump.
  3. Antec KÜHLER H₂O 1250 – high-performance liquid cooling featuring a double slot slim radiator cooled by two 120mm fan PWM powered and regulated. The water flow is guaranteed by a two water pumps.

For this test and review I received Antec KÜHLER H₂O 650, which is the smallest version, so enough with the information regarding the series, it is time to do some reviewing and if everything is alright, some testing…

The front side of the package The side/back of the package
IMG_8874 IMG_8876

Antec KÜHLER H₂O 650 was provided to me in the pretty standard for the KÜHLER H₂O series (except for the newest models) carton box painted in black/grey/blue with a big picture of the product itself and some technical details on the front side of the package. The full technical specifications as usual are on the side of the package, while the back side is used for additional information in several languages about the technologies used so this product can be created. A package which looks pretty nice but for now let’s put it aside and check the content inside of it.


Typical for all of the AIOs from the company, the water cooler and all of the additional accessories are carefully packed in nylon bags and secured in a carton bed. On top of the parts there is a high density foam sheet protecting the AIO water cooling system and an installation manual. All of the bags and the foam sheets are only meant to provide maximum protection and deliver the product in one piece. Job done, so let’s remove them and check the AIO already…

And these are all things which I found inside the carton bed arranged for picture…


The standard package offers:

  1. Combined, entirely painted in black backplate needed for all Intel and AMD sockets.
  2. Combined, entirely painted in black metal frontplate needed for all Intel and AMD sockets.
  3. 4 rubber parts needed to secure the position for Intel or AMD sockets on the frontplate.
  4. 4 long push and screw bolts for installing on Intel sockets
  5. 4 long push and screw bolts for installing on AMD sockets using the backplate provided with the AIO
  6. 4 additional long push and screw bolts for installing on AMD sockets if the original backplate of the motherboard is used. A pretty nice feature to be honest.
  7. 1 painted in black plastic frame to be installed if a second fan isn’t installed on the radiator.
  8. 4 long bolts painted in black for installing an additional fan to the radiator and installing the radiator to the case
  9. 4 additional short bolts for installing the radiator directly to the case fan slot.
  10. 4 x rubber dumpers for sticking the backplate to the motherboard
  11. An installation manual

I believe the time has arrived to check out the AIO water cooling system itself.

After I took all of the parts out of the carton bed the first thing which drew my attention was the new, a bit changed water block, which for this model is a bit thinner and completely missing the water pump. Since the pump is not on the back side of the water block it is attached to the fan, but I will talk about this a bit later. Overall the 2 new features make the AIO a pretty interesting product. Apart from that it offers a pretty standard structure for an all-in-one water cooling system featuring of course a cooling plate, a cooling radiator, 2 tubes, cooling fan with the pump attached on its back and the mounting kit. Of course, to do a proper review I will check them all one by one.

So let’s get started…

Cooling radiator


Antec KÜHLER H₂O 650 offers a pretty standard cooling radiator made of aluminum entirely painted in black with a slim design and overall dimensions of 159 mm x 120 mm x 27 mm. The slim radiator offers a fin array with 2 mm fin gaps for optimal heat dispersion and is meant to be used with up to two high pressure 120 x 25 mm fans installed on both sides of the radiator. And here comes the first interesting part.

Cooling fan

The fan/pump seen from the front
The fan/pump seen from the side
IMG_8887 IMG_8889

The standard Antec KÜHLER H₂O 650 package features just one 120mm fan based on Liquid State Bearing and made of half-height square frame painted entirely in black and a propeller with 7 very large with very small angle blades, meant to provide nice and stable airflow and static level pressure. The fan is pre-installed on the radiator with reversed frame/propeller installation method made to blow the air forward through the fins array and in order to remove the fan from the radiator you should also detach the tubes for the water pump. A job which should be done only by people who know what they are doing. According to the official details the fan is meant to work at 600 – 2400 revolutions per minute range providing airflow level range of 42 – 166.8 m³/h, static level pressure of 0.3 – 4.8 mm3-H2O at noise level of 16 – 38 dBA PWM powered and regulated. Pretty serious technical specification to be honest…


Maybe you have already noticed that the water pump in the new models from the series is installed on the back of the fan, instead of on the back of the water block. And here comes the interesting part. The motor of the pump is installed right behind the fan motor using the same plastic bracket and according to the official technical details operates at 3000 revolutions per minute and offers a Ceramic Bearing. Pretty inovative idea, which actually may do some serious cooling and unfortunately hard to replace the fan if it is needed. The fan motor is PWM powered and regulated, while the pump motor is powered with maximum voltage for constant speed, which should provide the best possible performance/noise balance all the time. Apart from that on the back side of the radiator a second 120mm fan could be installed, which will be a regular fan for boosting the overall performance of the AIO.

Cooling water block and the tubes

The water block seen from the top
The water block seen from the bottom
IMG_8884 IMG_8893

Antec KÜHLER H₂O 650 features a round, pretty simple water block compared to the other AIOs on the market, and is made of 3 components. The first one is the actual square, perfectly milled copper contact plate made to absorb the heat from the processor and transfer it to the water inside the loop. The second part is the round, painted entirely in black plastic cap with a semi-transparent smaller circle in the middle. Of course the name of the company is right there in the middle. The smaller circle is the part through which we can see the integrated LED backlight, which changes its colour according to the temperature of the water inside the system. The third part is as I believe the electronics featuring the PWM power and regulation, the backlight and a thermal probe installed inside the loop. When all of the parts work together, they do the magic and keep all modern processors cool providing stable performance.

The assembly of the copper contact plate and the plastic cap is done by 12 bolts, which should stay hard fastened all the times as you can see from the pictures above.

The connection between the radiator and the water block is done by two very flexible rubber tubes with length of 300mm, as usual painted in black. Even though they are a bit long their flexibility is meant to provide nice and smooth installation inside almost every modern case.

All of the AIO cables The fan/pump connected
IMG_8894 IMG_8896

To power the AIO all we should do is connect the first cable coming out of the water block with the CPU fan header on the motherboard and later connect the fan installed on the radiator to the second cable coming out of the water block and enjoy the cool and quiet operation. The second cable meant to provide the voltage for the fan/pump to operate provides a second connector for a second fan, which could be installed on the radiator. Pretty simple and reliable setup.

So far so good. Everything looks pretty amazing but without a proper mounting kit it would be a useless product. So let’s pay some attention to the mounting kit.

Mounting kit

According to the official technical details at the Antec web page, KÜHLER H₂O 650 is supplied with all of the parts needed so this system can work with:

  1. Intel LGA 775/1150/1155/1156/1366/2011
  2. AMD AM2/AM2+/AM3/AM3+/FM1/FM2

Of course, for doing the tests I will need the AMD brackets and these are the parts needed so the AIO can be installed on my motherboard:


Now let’s start assembling the mounting kit.

As I said earlier in the article, the official package offers 4 long push and screw bolts for installing on Intel sockets, 4 long push and screw bolts for installing on AMD sockets using the backplate provided with the AIO and 4 additional long push and screw bolts for installing on AMD sockets if the original backplate of the motherboard is used. And here I want to salute Antec for providing such an option. Pretty nice feature.

Anyway, for my test and review I decided to go for the second type of bolts and use the backplate provided with the AIO. So let’s prepare it for installation.

The mounting kit parts The backplate is ready
IMG_8902 IMG_8904

The first thing to do is to install the four metal nuts in the four corners of the backplate which later will be used to fasten with the bolts holding the water block. Second thing to do is to install 2 rubber pads meant for AMD which will stick to the backplate and the back of the motherboard. Thus the backplate won’t fall when installing the water block. And here I want to point out that there are 2 more rubber pads which should be used for Intel.

Next thing is to prepare the front metal plate, which will hold the water block with enough pressure to the processor. The front plate is actually combined for both Intel and AMD and to prepare it all we should do is move the side parts around the 2 metal circles and later fix them with the 4 rubber parts. And here I want to point out that the front plate has six small metal parts which should fit in six small channels around the round plastic cap of the water block.  Pretty nice idea and very easy to use front plate!

And this is what the mounting kit looks like when all of the parts are together…


With the backplate ready, let’s proceed with the installation…


And this is what the water block looks like when installed on the motherboard. According to the picture above, we can’t even think of RAM slots block. Pretty nice…

Next step is to install the radiator inside the case.


Since Antec KÜHLER H₂O 650 arrived with just one fan and 4 long bolts, so to install the radiator I will use the provided in the package black frame. Of course, I could install the radiator with the shorter bolts, but I prefer it this way. Of course, the frame can be replaced with a second fan to boost the overall cooling performance.

I believe I am done with the review of the water cooling system and all of its parts and now it is time for testing. And to do the tests I want to describe the system I am going to use.

Test rig:

CPU: AMD Vishera FX-8350

  1. At standard frequency 4.020 MHz (at 1.356V)
  2. At low overclock frequency of 4.220 MHz  at 1.380V)
  3. At medium overclock frequency of 4.420 MHz (at 1.416V)
  4. At high overclock frequency of 4.720 GHz (at 1.452V)

Motherboard: GigaByte 990FXA-UD3

Video card: 2 x Gigabyte GV-R927XOC-2GD

Memory: 2 x 4GB Geil Black Dragon 1866 MHz

Hard drive: Kingston SSD SV100S264G

Case: SilverStone Raven RV-03

Power supply: Antec HCP-750W

Cooler: Antec KÜHLER H₂O 650

Thermal paste: The pre-installed thermal compound

Fan mounted:

For this test and review I am going to use the standard fan working at automatic PWM control between 600-2400 revolutions per minute providing airflow level range of 42 – 166.8 m³/h, static level pressure of 0.3 – 4.8 mm3-H2O at noise level of 16 – 38 dBA.

The tests were conducted in a closed system with:

  1. 2 x SilverStone AP181 – 180mm fans on the bottom panel putting fresh air in and spinning at about 1200 rpm
  2. 120mm fan behind the motherboard cooling the socket and spinning at about 1000 rpm.
  3. Room temperature of about 18 degrees.

Both of the SilverStone AP181 – 180mm fans were connected together to the chassis 1 connector and were rotating at maximum speed.

Testing procedure:

I will install Antec KÜHLER H₂O 650 and do stress tests at standard frequency of 4.020 GHz (at 1.356V), at low overclock frequency of 4.220 GHz (at 1.380V),  at medium overclock frequency of 4.420 GHz (at 1.416V), and at high overclock frequency of 4.720 GHz (at 1.452V) using only the standard fan PWM powered and regulated.

And this is what the AIO looks like when installed inside the case and ready for testing…

With left panel open With left panel closed
IMG_9115 IMG_9117

And this is how the cooler operates when some load on the processor is applied:

Now let’s check out the test results:

KÜHLER H₂O 650 1 FAN@4020MHz 1.356V KÜHLER H₂O 650 1 FAN@4220MHz 1.380V
Antec Kuhler h2o 650 1FAN@4020MHz 1.356V Antec Kuhler h2o 650 1FAN@4220MHz 1.380V
KÜHLER H₂O 650 1 FAN@4420MHz 1.416V  KÜHLER H₂O 650 1 FAN@4720MHz 1.452V
Antec Kuhler h2o 650 1FAN@4420MHz 1.416V Antec Kuhler h2o 650 1FAN@4720MHz 1.440V

All of the test results have been summed up in the following charts:

Results T

And the fan speed during the tests:

Results R

With the test results added to the article it is about time to share my conclusions.

1. Antec KÜHLER H₂O 650 performance:

After I spent some time unpacking the all-in-one water cooling system and all of the additional accessories packed inside the box, arranging them for taking pictures, installing the cooler and finally after I’ve finished testing I can say that Antec KÜHLER H₂O 650 is one really innovative, interesting, very attractive and very well-performing budget AIO water cooling system made to provide stable and reliable performance for a long time, guaranteed by its build quality and features.

The cooler itself offers pretty unique AIO design featuring an entirely new type of water pump installation, attached directly to the back of the fan and using the same plastic bracket but with two separate motors, working at 3000 rpm for the pump and in 600-2400 rpm range for the fan. And here is something which I believe is important. When I do my tests I always set up the fans at maximum speed to show the product’s maximum performance and here I saw something very nice. The voltage between the CPU fan header and the AIO was 12V, which for every product should provide maximum fan speed, while for Antec KÜHLER H₂O 650 I believe the pump was rotating at maximum speed, but the fan was PWM regulated. For that reason the fan speed shown on the pictures above was far away from its maximum speed. And since AMD FX-8350 overclocked at 4.7Ghz was not enough to make the fan work at 2400 rpm, I wonder how hot the processor should be to make the fan rotate at 2400 revolutions per minute. Apart from that here is something which made me think. If the smallest model works like this, how will the 1250 version will operate with this processor? A question which remains…

After all of the tests are done I can say that Antec KÜHLER H₂O 650 offers very serious performance and handled to keep even that power hungry beast – AMD Vishera FX-8350 operating even at 4.7Ghz per core, which makes me think that it will be able to keep every modern processor working with load at default, overclocked or even extremely overclocked frequencies.

2. Antec KÜHLER H₂O 650 appearance:

Antec KÜHLER H₂O 650 is made to offer very nice and stylish design combined with very innovative looking fan/water pump which when working inside a black case offers pretty nice visual effect and that can be a base for a very good looking personal computer or a modding project in a black/white colour scheme. Apart from that the integrated temperature LED backlight on the water block adds an additional visual effect and a feeling of the product’s reliability.


Official price (MSRP) for  Antec KÜHLER H₂O 650:  69.95 euro

Official warranty: 36 months

I thank Antec for the test sample.


Antec KÜHLER H₂O 650 – Test and Review
7.5 Total Score
Very good compatibility/ performance/ noise level balance

Noise level
Additional accessories
User Rating: 2.8 (1 votes)

Dobrin Krastev is the owner, reviewer and newsman of with more than 15 years' experience in personal computers, server and storage systems, UPS, peripheral devices and software. Passionate about testing and reviewing, AMD overclocking using AM3 990FXA and AMD FM2 A85X test systems and building modding projects.
  1. Reply Smokey 06.06.2016 at 21:39

    When I first turn on my PC the LED is shows white but after a few minuites it turns blue. Is this a bad thing?

    • Reply Dk_vr 10.06.2016 at 7:31

      Actually this is normal since the LED will change according to the temperature of the processor.

  2. Reply raymond 30.05.2015 at 13:58

    Hi! I would like to know how much wattage these coolers use? So that I can plan ahead what power supply to buy. Thanks!

  3. Reply fetskuli 07.05.2015 at 17:59

    I hapen to have the same processor and Cooler. At first it was good and my temps were low. Now my iddle is about 40-50c and when i play dota 2 for example my temps goes up to 80c (according to core temp)
    I apprecite any help!

    • Reply Dk_vr 13.05.2015 at 9:13

      Hello mate,
      I am sorry for the late reply but I’ve been extreme busy these days.

      This is interesting situation and could be cause by several different things:

      1. The ambient temperature in the room increased.
      2. It is possible the thermal compound is more dry and should be replaced.
      3. Your motherboard started delivering higher voltage to the processor.
      4. The contact between the processor and the AIO waterblock is lose.
      5. You need to clean the case from dust. That includes the fans and the AIO radiator.

      Check these and I believe the situation will get better.

  4. Reply Antonio 03.05.2014 at 1:45

    Thank you for the review, I’m buying the big brother…

    • Reply Dk_vr 24.06.2014 at 10:51

      Share with us what performance it will achieve or already achieved 🙂

  5. Reply Dimcho 28.04.2014 at 8:47

    Nevertheless this review is very well done, and I love when a video is included. Keep up with the good work 🙂

  6. Reply Dk_vr 28.04.2014 at 7:43

    Hello and welcome to

    That is one really good question….
    Unfortunately I can’t say with exact numbers how much better the new model is because: Antec Kuhler 620 was tested on a processor – AMD Athlon 2 x4 620 (95W) without overclock, which I don’t use anymore. A quad core processor which was not so power hungry as the AMD FX8350 (125W) without overclock.

    Anyway lets try doing some calculations:
    AMD Athlon 2 x4 620 (95W) vs AMD FX8350 (125W) is like 24% more power consumed for the second processor
    max temp for Kuhler 620 at the test was 50 degrees, while for Kuhler 650 it is 58 degrees, which make 14% high temp result.
    And if my calculations are right, I am not really good with mathematics, that should be 10% higher performance. Of course these are just a thoughts and noone can guarantee it like this…

    Best Regards

  7. Reply jamtrix 27.04.2014 at 11:22

    How is this compared to Antec Kuhler 620? And around how many percent, in terms of performance, this current Kuhler 650 have over its predecessor, Kuhler 620?

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