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 & the Cooler Testing Results & Conclusion
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  • FreckledTrout - Monday, February 7, 2022 - link

    It will work in low airflow or fully passive. Both should work fine with this cooler. It would simply depend on your objectives. If you wanted 100% dead silent, as in middle of a recording studio quiet, then this could make a decently powerful build. Reply
  • RSAUser - Monday, February 7, 2022 - link

    If you're in a recording studio, then you'd run the cabling from another room. Reply
  • Oxford Guy - Tuesday, February 8, 2022 - link

    The electrical noise from a system I put together that’s in an adjacent room is loud enough to inflame my tinnitus.

    My assumption is that the bulk of it is coil whine from the Fury X GPU.

    I am using a passive system right on my desk and it doesn’t bother me at all.
    Reply
  • RSAUser - Monday, February 7, 2022 - link

    Just to add other use-cases: e.g. dusty area. Reply
  • Jon Tseng - Tuesday, February 8, 2022 - link

    Yeah, depends what you want. If you want to have a system with enough horsepower to game (dGPU) even even with a fully passive CPU and GPU you likely need at least some casefans to get airflow thru the device.

    On the positive side it means you can put in a larger / quieter fan at the case level so its /virtually/ silent - but at the moment its still hard to make a zero-moving-parts system.

    I you were shooting for something lower power (HTPC w no dGPU?) I guess it maybe possible? At worst you could try and dig up one of those funky cases which act as a giant heat sink? (do they still make them?)
    Reply
  • Spunjji - Wednesday, February 9, 2022 - link

    "do they still make them?"
    Yup! MonsterLabo even do "The Beast" which claims to cool 150W worth of CPU heat and 250W on the GPU without fans, while Streacom have a whole range of fanless HTPC chassis designs.
    Reply
  • bogda - Tuesday, February 8, 2022 - link

    If the system is not completely passive cooled, why would anyone choose this over nearly completely quiet, similarly priced NH-D15? Reply
  • GL1zdA - Tuesday, February 8, 2022 - link

    If you can manage airflow without the NH-D15 fans, then such build might be quieter. I really wish there was a second part of the review, which would test operating such setup. Reply
  • Oxford Guy - Tuesday, February 8, 2022 - link

    Tower coolers designed for very low RPM fans have wider fin spacing. Thermalright’s Macho RT is probably an example. Reply
  • Oxford Guy - Tuesday, February 8, 2022 - link

    Cleaning the dust out of those is no fun. Reply

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