Testing 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, steady and variable, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it would be 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 much 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 and or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60 W and 340 W, in 2 W 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 the 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, their measurement is being performed only manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being acquired via a laser tachometer. The fans (and pumps, when applicable) are being powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1 meter 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.

The noise floor of our recording equipment is 30.2-30.4 dB(A), which represents a medium-sized room without any active noise sources. All of our acoustic testing takes place during night hours, minimizing the possibility of external disruptions.

<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper-slight humming)
38-40dB(A) Quiet (relatively comfortable - humming)
40-44dB(A) Normal (humming noise, above comfortable for a large % of users)
44-47dB(A)* Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (painfully distracting for the vast majority of users)
>54dB(A) Intolerable for home/office use, special applications only.

*noise levels above this are not suggested for daily use

The Alphacool Eisbaer 240 CPU Liquid Cooler Testing Results, Maximum Fan Speed (12 Volts)
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  • MobiusPizza - Monday, August 1, 2016 - link

    The author says this cooler has best noise/thermal performance ratio, but looking at the graphs the CoolerMaster H110 seems to have both lower noise level and lower thermal resistance?
  • retrospooty - Monday, August 1, 2016 - link

    Yeah, I am really not getting the need for water cooling these days. Today's Core i5/i7 CPU run extremely cool... Even if you are overclocking, there are little to no benefits of using water. It adds complexity with no benefit. I have a Core i5 Skylake with a BeQuiet shadow rock 2 cooler, and I dont even plug in the fan at all. I can run prime - 100% CPU utilization for hours and hours with no fan at all and it doesn't even get warm, not even a little... and I live in Arizona and its summer. There just isnt a need for water anymore, even if you are overclocking the hell out of it.
  • nightbringer57 - Monday, August 1, 2016 - link

    Think about people still rocking a good old FX8350 like me ;)

    And AIO watercooling still happens to be competitive in high perf / small cases (typically mini ITX) setups, where clearance around the CPU is often very limited (typically, the PSU is in the way and forbids anything but very low-profile coolers), but can fit 1 or 2 12cm fans.
  • retrospooty - Monday, August 1, 2016 - link

    Agreed, if you have an AMD CPU, you can benefit from water cooling. Some high end video cards as well... but AMD CPU's and high end video cards get hot as hell. My comment was on Intel CPU's. I would have a hard time recommending anyone buy an AMD CPU these days, regardless of the cooling used. Hopefully the upcoming Zen processor changes that. It would be great to go AMD again if they can be competitive.
  • nightbringer57 - Monday, August 1, 2016 - link

    edit: and Intel power consumption climbs up if you get into the more high-end platforms (like the X79/X99 platforms). Especially on tinier mainboards (think: mini ITX X99 ones) where you don't have standard cooler mounting holes but the special I-can't-remember-the-name ones. In those cases, big coolers don't fit. But a waterblock happily does.
  • retrospooty - Monday, August 1, 2016 - link

    I dont know... My core i5 6600k cooled as described above is a Mini itx case. Even if it were a smaller case, with no room for a huge tall cooler, there are options that work great.
  • nightbringer57 - Monday, August 1, 2016 - link

    It depends on your case.
    And as explained, your i5 is not realy an "enthusiast" CPU, even if it's a great CPU in itself.
    And the options that work great in more confined cases... Do not work quite as great as your typical AIO watercooling system, even if those have difficulties getting significantly better results than average-to-high-end aircooling systems.

    It's a niche, yes. But I wouldn't say this niche doesn't exist.
  • retrospooty - Monday, August 1, 2016 - link

    Agreed, in some cases water would be better, AIO cases is a good example... But if you buy an AIO with water cooling, it comes pre-built and you dont do anything with it... The product above would not be for that. Also, if you have an older system you want to keep and improve the old air cooler, it might be good too depending on what you have... I guess what I am getting at, is if you were putting together a new system as of today (as opposed to upgrading an older one) you would be better served to by a case and an air cooler. They have tons of options of all sizes. Let me put it another way, if were building a new system as of today and you chose parts (case and CPU) that would benefit from water cooling, you probably chose badly.
  • nightbringer57 - Monday, August 1, 2016 - link

    When I say "AIO", I mean "AIO liquid cooler" (such as in this review), not "AIO computer" ;)

    And no, cases that cannot fit a good air rad (so limit the choice to either low profile rads or AIO liquid cooler) simply allow you to have a more compact PC, so they are not a bad choice, they answer different needs.
  • retrospooty - Monday, August 1, 2016 - link

    Got it... I am paying attention LOL ;) I do see your point, I just dont think alot of people have that need. Like I said, if today (and that today part is a key thing here) were building a system, I cant see picking any case and CPU that would require something like the product above. If you are into massive overclocking, a tiny mini ITX case that cant fit a normal size air cooler probably isnt the best choice. There are plenty of mini ITX cases that can fit air coolers of any size and need. If you are overclocking and need something really small that cant fit a full size air cooler, OK... But if that is the case someone chose, where would they put the radiator? I know there are answers to that question and ways to do it, but extreme niche is what I am hearing.

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