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 manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being recorded 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

Introduction, Packaging & Bundle Testing Results
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  • jabber - Saturday, January 16, 2021 - link

    Hmm interesting. I just this week replaced my Arctic Cooling 240 MK1 AIO with a Noctua NH-D15S. The result was pretty much the same cooling but about 60% less noise. A success in my book. Nice easy installation too. The only change was I used my Grizzly paste rather then the tube of Noctua supplied.
  • Makaveli - Saturday, January 16, 2021 - link

    I've not had any noise issues at all on a Corsair H150i 60% less noise with a D15S? sounds like that AC 240MK1 AIO is junk.
  • jabber - Sunday, January 17, 2021 - link

    4x120mm fans on the AC AIO down to 1x140mm fan on the Noctua. Not hard to imagine really.
    The 60% is not a measured figure, shall we say "a lot quieter!"
  • Makaveli - Sunday, January 17, 2021 - link

    Except the AC240MK1 is a 240MM AIO which means 2x120mm Fans. He never said he has the 420mm model which is what you are using for an example in your post. Nice try though.
  • jabber - Sunday, January 17, 2021 - link

    In that case I have the version with 4 120 fans. The Artic Liqid Freezer 240 with 4 fans.


    So yeah, nice try.
  • Makaveli - Monday, January 18, 2021 - link

    I wouldn't expect a 4 fan 120mm AIO to be quiet. A 3 fan 140mm AIO would make less noise than that.
  • brontes - Saturday, January 16, 2021 - link

    I'm not sure about non-PC radiators but in the PC space, crossflow (or "xflow") refer to rads that have the inlet and outlet on opposite ends. This is single pass. While less performant than dual pass, it's not as bad as you'd expect as it's much less restrictive and will yield a higher flow rate at a given pump speed(/noise level.) The primary use case is for cleaner/less tubing, depending on the case layout.

    The alternative is your standard dual pass where the water runs to one end, turns around, and runs across the rad again. Inlet and outlet are on the same end.

    At least in the PC realm of parlance, there is no such thing as a "dual-pass cross-flow design."
  • micoequipment - Monday, January 18, 2021 - link

    Great Awesome blog. It's so informative and I love this type of blog and articles.
  • Tom Sunday - Tuesday, January 19, 2021 - link

    Yes there is lot to glean from blogs and the feelings of the many. But also a lot o read between the lines and simply cutting through the minutiae. I am just amazed that the AIO manufactures have not come up with any 'new products' and just adding lighting, better hoses, pump head configurations, etc. Todays AIO's are far from where they should be.
  • Oxford Guy - Tuesday, January 19, 2021 - link

    Be specific. What do you think they’re lacking?

    My view is that they’re being applied to the wrong thing. GPUs need them far more than an efficient CPU like recent Zen.

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