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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jmke - Wednesday, February 12, 2014 - link
as with everything, the noise scale and extreme focus of SPCR does give a slightly twisted view.none of these AIO would qualify as silent, anything above 30dBA would be loud for him; his kitchen is <30dBA... ;-)
EnzoFX - Wednesday, February 12, 2014 - link
>30DB is loud lol. At least audible to anyone I would say, so can't we at least say it's not silent? Furthermore he'd provide at least a vast array of reference points, where Anandtech is severely lacking when it comes to cooling/cases/etc.E.Fyll - Wednesday, February 12, 2014 - link
Definitely not loud and not even audible to most. 30 dB(A) is the lowermost threshold that the vast majority of sound level meters can take a reading from. I have provided a thorough explanation about this down below in the comments. I personally consider any test that I have seen stating that they got a valid reading below 30 dB(A) with sub - $30k equipment to be rubbish.Jon-R - Wednesday, February 12, 2014 - link
So you're saying that the tests over at SilentPCReview are rubbish? What sound measurement equipment did you use? I couldn't find a mention of it.JlHADJOE - Thursday, February 13, 2014 - link
30 dB is very quiet far as background noise goes.Whisper Quiet Library at 6' 30dB
Sauce: http://www.gcaudio.com/resources/howtos/loudness.h...
JlHADJOE - Friday, February 14, 2014 - link
It's not so much that their tests are rubbish, just unrealistic.SilentPC tests in an anechoic chamber, so the noise floor when they test is near zero. Compared to that, an increase to 30dBA is very loud. But in a real-world environment, 30dBA is whisper quiet.
I do agree though that use of the anechoic chamber keeps their tests consistent and repeatable. Just not necessarily representative of what a case will actually sound like in a real room.
YazX_ - Wednesday, February 12, 2014 - link
Thx for this thorough review, i have corsair H100i, its awesome AIO cooler, but the fans are piece of shit and very noisy, i replaced them with Bitfenix LED ones, although they operate at 1800 RPM, but i never had to see them operate on that speed, my CPU is OCed to 4.5Ghz and max temp is 65, so they work 50% most of the time and pretty silent.AshyPistachios - Wednesday, February 12, 2014 - link
This ended up comparing fans more than it did rads/pumps. I would like to see a test scenario where identical fans are used on each rad. The current testing methodology does test the complete package, but people seeking silent setups tend to swap all of the fans anywayMrSpadge - Wednesday, February 12, 2014 - link
Agreed - comparing performance doesn't mean much with such different fan noise levels. You could use some high pressure fans for all systems, for example.And I couldn't care less if a stock fan runs at 7 V or what ever. What I do care about is the noise. In practice I set my rigs up for the best cooling I can get at subjectively low noise level (they're running 24/7 under load). So pick any reasonably quiet noise level, set the fans to whatever speed is required to get there and then compare performance (note: this is even more meaningful if you use similar fans). With PWM you're not limited to 12V and 7V, it's not 2005 any more.
E.Fyll - Wednesday, February 12, 2014 - link
7 Volts is about the same voltage level as most modern motherboard apply in their "quiet" mode. High enough to start nearly all fans ever made, low enough to keep things quiet. Unfortunately, I cannot perform testing the way you propose. As you mentioned yourself, it would have to be a "subjectively low" noise level. The very word "subjectively" puts me off. Even if I do set such a noise limit, which would be terribly wrong as it would just be based on my subjective opinion, not all coolers would be able to operate as such a noise level at all.It is even less meaningful to use the same fans; when you are buying a kit, you are buying the kit with its fans. Purchasing additional fans not only raises its cost but, depending on the characteristic behavior of the fan, the fan itself can affect performance and favor some kits over others. The actual performance of a fan is not based on its RPM or CFM ratings, it is a very complicated matter. That would render any comparisons between different kits virtually useless. Furthermore, the choice of fans would be based on my subjective opinion as well, nobody warranties that the end user will be purchasing the same fans out of the hundreds of possible choices. Someone would want me to use a quieter fan, others might want something more powerful, others something cheaper, others something fancier and so on. And of course, most would just want to buy a kit and be done with it. The only objective comparison is to compare the performance of a kit with its stock fans, as it comes supplied from the factory. Everything else is based on assumptions and subjective opinions that, including mine, have no place in an objective review.