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 NZXT CAM Software Testing Results
Comments Locked


View All Comments

  • brontes - Wednesday, August 19, 2020 - link

    When it comes to mixing water and electronics, nobody wants to mess around with unproven stuff.

    It works the same way in custom loop stuff. There are as many rebadges of the
    asetek aio as there are the D5 and DDC custom loop pumps. https://laing-thermotech.com/industrial-commercial...

    But I agree, after time the mix and match of each part provides a known quantity in terms of performance, which isn't bad. But it makes for a boring review. Kind of like the Lego style designs in midrange ssds.
  • brontes - Wednesday, August 19, 2020 - link

    edit: Retest all these aios using the same fans instead of the included and I bet they would perform within margin of error of each other. Fan pairings make a much more apparent difference on a rad than a standard heatsink.
  • Guspaz - Wednesday, August 19, 2020 - link

    For that matter, any cooler review without noise-normalized testing is useless (who cares how well it performs at max fan speed, those aren't the same noise levels and can't be compared) and this review didn't include that. It does mitigate this with the thermal resistance versus sound pressure test at the end, but that doesn't really provide a convenient point of comparison, nor does it tell the user "How hot will my CPU run at a reasonable sound level."
  • rpg1966 - Thursday, August 20, 2020 - link

    It's extraordinary that their cooler tests don't have a simple x-y chart of noise/dB versus CPU temp.
  • E.Fyll - Thursday, August 20, 2020 - link

    Page 4, last section.
  • TelstarTOS - Thursday, August 20, 2020 - link

    of only 4 models.
  • alufan - Thursday, August 20, 2020 - link

    I dont understand why they dont test them all at a set RPM forget all the pwm stuff wire them i via a fan controller and set them at say 800 RPM and see which actually shifts the heat, my Custom loop rarely hits anything more than 750 rpm and my CPU is under 50deg C no matter what I do with it
  • Guspaz - Thursday, August 20, 2020 - link

    RPM is irrelevant. Performance at a fixed noise level is what matters, because a cooler that comes with noisy fans and a cooler that comes with quiet fans shouldn’t be weighted equally if they cool as well at the same RPM.
  • TelstarTOS - Thursday, August 20, 2020 - link

    "any cooler review without noise-normalized testing is useless"

    QFT. This review is almost useless and subpar for AT usual level of completness.
  • GNUminex_l_cowsay - Wednesday, August 19, 2020 - link

    Don't retest these AIOs with the same fan. The brands that include inappropriate fans with their AIOs deserve the consequences of their poor decisions.

Log in

Don't have an account? Sign up now