First let’s see how the performance of the Antec KÜHLER H2O 620 varies depending on the direction of the fan’s air flow and the presence of a second fan. So, there are three test modes: the default configuration with one fan exhausting the air out of the system case (the red graph called Outtake); a single fan is set to drive air into the system case through the radiator (the green Intake graph); two fans are set to drive air into the radiator and exhaust it out of the system case (the blue graph). The second fan was a Noiseblocker NB-BlackSilent XLP. Its impeller is similar to the impeller of the cooler’s default fan. The fans had the same speed set by means of manual controllers.
Here are the results:
It is clear that the recommended positioning of the default fan is not optimal in terms of CPU cooling. When the fan is simply turned over, the peak temperature of the hottest CPU core lowers by 3-4°C in the quiet mode, by 2°C at medium speeds, and by 1°C at the maximum speed. However, the hot air from the radiator has to be effectively exhausted from the system case by other fans then.
The installation of a second fan on the radiator improves the KÜHLER H2O 620 further. Now it can cope with the six-core CPU even at the minimum speed of 600 RPM. The speed being the same, the dual-fan setup is 6 to 10°C better than the single-fan ones! The gap narrows at the maximum speed, yet still amounts to 4-5°.
Now let’s compare the Antec KÜHLER H2O 620 with a Thermalright Archon. Since we’ve already learned how the performance of this liquid cooling system depends on the speed, number and direction of its fans, the next diagram shows its results in its default configuration (one exhaust fan) as well as with two fans at three speeds (1000, 1600 and 2000 RPM).
At the lowest speed of its single default fan the Antec KÜHLER H2O 620 is 16°C worse than the Thermalright Archon under peak load and doesn’t even keep the CPU stable. Increasing the fan speed to the maximum 2000 RPM doesn’t help it beat the Archon, either.
When equipped with two fans, the Antec KÜHLER H2O 620 can be as good as the Thermalright Archon but only if the fans are rotating at 2000 RPM, which is much louder than the single Thermalright TY-140 fan rotating at 1280 RPM.
Talking about noise, I should say that the pump of the liquid cooling system works very quietly, almost silently. It was perfectly inaudible against the noise from the default Antec fan at 800 RPM. As for the fan itself, I guess the manufacturer should have lowered the bottom speed limit from 1450 RPM (1420 RPM according to my monitoring tools) to 800 RPM. This would make the Antec KÜHLER H2O 620 very quiet, at least at low CPU loads. In its current implementation, this liquid cooling system is rather noisy.
We have tested a number of compact liquid cooling systems similar to the Antec KÜHLER H2O 620 in our labs but all to the same effect: a high-quality air cooler of the same or even lower price is going to be more efficient and quieter. The examples include Enzotech Ultra-X, ZEROtherm NV120 Premium, Thermalright IFX-14 twice (click here for the second encounter), Cooler Master Hyper 212 Plus, Thermalright Silver Arrow and now Thermalright Archon.
While air coolers have been steadily developing and improving, offering higher performance at lower noise, we can’t say the same about compact liquid cooling systems. Their manufacturers all make the mistake of equipping their products with small single-piece radiators, so that there is a linear dependence of the cooler’s performance on the speed of its fan, leading to an increased level of noise. The Antec KÜHLER H2O 620 is no exception. Nevertheless, even though this model offers average cooling efficiency and is pretty loud, we must point out such indisputable advantages as its compact size, wide compatibility, simple installation and low price (for a liquid cooling system).