Closed Loop AIO Liquid Coolers: 14-way Mega Roundup Review
by E. Fylladitakis on February 12, 2014 7:00 AM ESTTesting Methodology
Although the testing of a cooler appears to be a simple task, that could not be much further from the truth. Proper thermal testing cannot be performed with a cooler mounted on a single chip, for multiple reasons. Some of these reasons include the instability of the thermal load and the inability to fully control and/or monitor it, as well as the inaccuracy of the chip-integrated sensors. It is also impossible to compare results taken on different chips, let alone entirely different systems, which is a great problem when testing computer coolers, as the hardware changes every several months. Finally, testing a cooler on a typical system prevents the tester from assessing the most vital characteristic of a cooler, its absolute thermal resistance.
The absolute thermal resistance defines the absolute performance of a heatsink by indicating the temperature rise per unit of power, in our case in degrees Celsius per Watt (°C/W). In layman's terms, if the thermal resistance of a heatsink is known, the user can assess the highest possible temperature rise of a chip over ambient by simply multiplying the maximum thermal design power (TDP) rating of the chip with it. Extracting the absolute thermal resistance of a cooler however is no simple task, as the load has to be perfectly even, with the ability to vary the load, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it were possible to assess the thermal resistance of a cooler while it is mounted on a working chip, it would not suffice, as a large change of the thermal load can yield very different results.
Appropriate thermal testing requires the creation of a proper testing station and the use of laboratory-grade equipment. Therefore, we created a thermal testing platform with a fully controllable thermal energy source that may be used to test any kind of cooler, regardless of its design or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60W and 340W, in 2W increments (and it never throttles). Furthermore, monitoring and logging of the testing process via software minimizes the possibility of human errors during testing. A multifunction data acquisition module (DAQ) is responsible for the automatic or the manual control of the testing equipment, the acquisition of the ambient and in-core temperatures via PT100 sensors, the logging of the test results, and the mathematical extraction of performance figures.
Finally, as noise measurements are a bit tricky, we're measuring these manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is acquired via a laser tachometer. The fans (and pumps, when applicable) are powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1m away from the cooler, in a straight line ahead from its fan engine. At this point we should also note that the decibel scale is logarithmic, which means that roughly every 3 dB(A) the sound pressure doubles. Therefore, the difference of sound pressure between 30 dB(A) and 60 dB(A) is not "twice as much" but nearly a thousand times greater. The table below should help you cross-reference our test results with real-life situations.
| Noise Level Reference Values | |
| <35dB(A) | Virtually inaudible |
| 35-38dB(A) | Very quiet (whisper) |
| 38-40dB(A) | Quiet (slight humming) |
| 40-44dB(A) | Normal (humming noise, comfortable level) |
| 44-47dB(A) | Loud* (strong aerodynamic noise) |
| 47-50dB(A) | Very loud (strong whining noise) |
| 50-54dB(A) | Extremely loud (level equivalent to a ≈1500W vacuum cleaner) |
| >54dB(A) * | Intolerable for home/office use; special applications only. |
* Noise levels above this are not suggested for daily use
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thewhat - Wednesday, February 12, 2014 - link
"the Corsair H90 ... is entirely silent when its fan's voltage is reduced down to 7 Volts."I've tried some of the quietest fans in existence and at 920 rpm they weren't even quiet, let alone entirely silent.
Anything over 600-700 rpm is usually audible, but quiet. And at around 800 rpm it stops being quiet.
Maybe we just have different standards for quietness.
But then liquid cooling was never a good option for silence freaks, anyway.
E.Fyll - Wednesday, February 12, 2014 - link
There are great differences between fans, even at same RPM, depending on their engine and wing design. This is also being displayed in this review, as fans running at nearly the same RPM have vast performance differences. At one meter away, I could not possibly discern any noise coming from the H90, that is why I classified it as silent. If however you were to install it inside a metallic case with many openings, which would reflect and enhance the noise level, you might be able to notice a low-tone humming noise - that's a maybe, a mere assumption on my part.Aikouka - Wednesday, February 12, 2014 - link
I don't know if anyone else considers it to be worthwhile, but I wouldn't mind seeing how well these coolers work when you remove one of the commonly-changed variables: the fans. I rarely ever use stock fans, and along those lines, it would be interesting to see what would happen if the same fans (per standard size -- 120mm and 140mm) were used on each cooler.jjj - Wednesday, February 12, 2014 - link
Pretty pointless without a comparison with the same fans and some air coolers.silenceisgolden - Wednesday, February 12, 2014 - link
I'm a little disappointed that patent trolls kept the Swiftech offerings from this list, but that's how things are I guess.casteve - Wednesday, February 12, 2014 - link
Thanks for the review. What was the ambient noise level and the noise meter used for the test?E.Fyll - Wednesday, February 12, 2014 - link
My apologies, I should have added this into the review. Will do so from now on. The meter is an Extech HD600 and the background noise level is 30.4 dB(A) (+/- about 0.5 dB(A), depending on the night I perform a test).casteve - Wednesday, February 12, 2014 - link
Thanks. As this meter has a lower limit of 30dB(A) and an accuracy of +/-1.4dB, your ambient is probably quieter and you are just seeing the low end of what the meter can do. Sort of expected unless (as you say) you have an expensive set up for the test equipment. Get Anand to shill out the $'s for a 10dBA microphone and an anechoic chamber for that spare bedroom. :)Some terms - if the meter is reading sound pressure level, then it's dB(A) SPL, which is referenced to 20 micro Pascals (0 dB). So, 0 dB(A) SPL is the threshold of hearing, 20-30dB(A) SPL is a calm room.
pcfxer - Wednesday, February 12, 2014 - link
All of these are way too loud. At 30+ dB, none of these coolers hit the envelope for someone who actually cares about "silence" and noise.E.Fyll - Wednesday, February 12, 2014 - link
You are confusing dB and dB(A), I am afraid. The background noise of my room at 2:00AM is 30.4 dB(A). Sub-35 dB(A) levels are generally impossible to notice by a human ear. Sub-30 dB(A) levels are next to impossible to record with anything less than science lab-grade equipment. There is no handheld or desktop dB(A) meter that can perform such readings. If you have seen reviews stating sub-30 dB(A) levels, make sure to check their methodology (given that there is any). Either the meter cannot read lower than 30 dB(A) (and/or will display a bogus reading, as most cheap Chinese meters do) and the review is a fictional text or their methodology is based on dB readings, not dB(A) readings, which is useless to a consumer.