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

The SilverStone Permafrost Series AIO Coolers Testing Results, Maximum Fan Speed
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  • PeachNCream - Wednesday, June 17, 2020 - link

    I can't see advantages in adding software and hardware complexity purely for lighting, but addressable RGB seems to be doing just that. More lines of code in which to make errors, more hardware that can fail, and a bigger software footprint for possible compromise and exploitation (nevermind the possible requirement of internet connectivity and awareness of said control software like Razer seems to require which is a by-design potential security problem).
  • eastcoast_pete - Wednesday, June 17, 2020 - link

    Agree! I wish reviewers could add (estimate) just how much the LEDs and associated hardware add to the BOM. I'd rather have an AIO cooler for $ 5 less with no lightshow.
    The only time any LED lighting of the cooling fans could be useful if they would activate or change colors with the CPU temperature (e.g. green, yellow, red); that would, at least, be of interest and tell me if the cooler is doing its job.
  • QB the Slayer - Wednesday, June 17, 2020 - link

    Well... as much as I agree. I do have a bunch of RGB stuff that I really only have since it came with the gear I purchased. But since I have it, I might as well use it! So I have ALL my RGB linked and it actually is linked to the CPU temp... Nice and cool blue when 45°C or less and burning hot red at 85°C or above. MB has 5, GPU has 20, AIO has 16, and mouse has 2... again nothing I went out of my way to get, but they are there. JackNet RGB Sync is a handy little app for this. All this does have a cost though... 3 apps must be running and they are not light in any way (iCUE, G HUB, and JackNet). Thankfully iCUE has an ASUS plugin so that doesn't have to run and the GPU and board can be linked with a cable so no app for the GPU either... Ugh, I am rambling now, sorry guys.

  • PeterCollier - Wednesday, June 17, 2020 - link

    Repeat after me: AIO cools no better than air and will leak.
  • PeachNCream - Wednesday, June 17, 2020 - link

    Would be nice to see a couple of air coolers in the benchmark charts just for the sake of completeness. I wonder if that would paint these liquid coolers in a poor light though.
  • BenSkywalker - Wednesday, June 17, 2020 - link


    AIO wins easily which shouldn't surprise anyone. The best air coolers can best the worst AIOs by a little providing you are ok with a cluttered sloppy build and rarely need to open your case for anything and you like having more noise.
  • khanikun - Wednesday, June 17, 2020 - link

    Imagine if they tested in a hot room. I have 3 desktops. 1 on custom loop and two on AIO (one Cooler Master and one Corsair). I use to live in Germany, where they don't seem to believe in A/C. So my computer room easily climbed into 85-90F. I couldn't keep any of my machines cool on air.

    I seem to be doing alright with my AIOs or my custom loop. My Cooler Master AIO was just $55. My Corsair AIO was $115. I have no idea how much my custom loop was, like $500. Owned each of them between 2-3 years now.
  • Lord of the Bored - Thursday, June 18, 2020 - link

    I can't imagine your computers running 85-90F in a room with no AC. Because that is sub-ambient right now where I am.
    Air conditioning is God's gift to Texas.
  • Lord of the Bored - Thursday, June 18, 2020 - link

    I misread that. Computer room != computer.
  • khanikun - Friday, June 19, 2020 - link

    Ya, computer room. My CPU sits around 30-35C for my custom loop (dual 360 rads/push pull fans), depending on whether it's winter or summer. My AIOs are in the 40s (240 rads/push pull fans).

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