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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  • abufrejoval - Tuesday, February 8, 2022 - link

    My biggest concern would be that nothing seems to anchor this mass except the motherboard. It might withstand 1kg of mass from the top, but a sideways mount is already exerting a significant shearing force. Now pick a system up and carry it between rooms or--heavens forbid--driving it around in a car...

    I've been able to keep noise levels at bay using mostly Noctua fans on my 24x7 machines, but I can sympathise with the want for 100% non-movable parts for reliability.

    E.g. my firewall is an i7 T part with 35W TDP using an 65Watt Noctua fan in a small form factor Mini-ITX chassis that's all perforated for fully passive Atom boards and nice airflow, but it can't keep the dust out. While I do vacuum the chassis regularly, obviously that doesn't reach into the fan itself and yes! one day the fan seized and the system shut off hard, thankfully without any noticeable physical or logical damage.

    Good thing I was home, though, not on one of these week-long business trips that I used to take before the pandemic. Having wife and kids diagnose and fix the issue over the phone would have been near impossible and the idea of facing a mob of 5 shut off the Internet for a week, makes such a fully passive system seem a bargain at almost any price.

    And here it's only twice the normal price for a Noctua.
  • FunBunny2 - Thursday, February 10, 2022 - link

    "My biggest concern would be that nothing seems to anchor this mass except the motherboard. "

    same thought. AT Folks: I suppose that MB manufacturers specify maximum shear/torque for vertical mounting (including 'weight' by lever distance, to put it crudely), and similar for horizontal. do MBs typically have passive holes surrounding the CPU socket such that standoffs can be screwed to the case/sub-frame?
  • 529th - Tuesday, February 8, 2022 - link

    This would be great for a daily / non-gaming rig. I use a Noctua NH-D15S chromax.black with near silent fans and it's fantastic. Actually I could probably not use any fans at all with the Noctua NH-D15S chromax.black. Either way it's always nice seeing this frontier pushed,

  • Oxford Guy - Tuesday, February 8, 2022 - link

    Tower coolers without fans perform poorly. Their fins are too dense and they don’t have the design elements needed to improve convection efficiency.
  • Oxford Guy - Tuesday, February 8, 2022 - link

    The hybrid models (widely-spaced fin towers) need some fan input to work efficiently.
  • kubafu - Tuesday, February 8, 2022 - link

    When you go for a silent PC I can't recommend Streacom cases enough. I've been a happy owner of DB4 case for the last 5 years and so far it's been a smooth and silent ride. In case of DB4 the whole case is a heatsink!

  • Duto - Tuesday, February 8, 2022 - link

    “Even before the first Pentium era of the early 1990s, PC CPUs were already powerful enough to require meaningful and capable cooling setups to keep their temperatures in check“

    Well, not exactly. The best way to put it would be:

    Even before the first Pentium era of the early 1990s, PC CPUs were already power-hungry and inefficient enough to require meaningful and capable cooling setups to keep their temperatures in check

    …with love
  • FLORIDAMAN85 - Thursday, February 10, 2022 - link

    I want this thing rising out of my mineral oil PC. Call it deep water horizon.
  • Foeketijn - Saturday, February 12, 2022 - link

    Zalman used to have these crazy designs. Passive cases (where the sidepanels of the case where the cooling bodies), watertowers, big passive blocks. I think that if they didn't blow themselves up, the whole PC cooling world would look totally different right now.
    I can't believe how few interesting AiO solutions are left. And Swiftech showed a decade ago how much is being left on the table.
  • COtech - Saturday, February 12, 2022 - link

    I love this objective test rig! I have thought for a long time that a proper test rig for coolers would be much better than building a whole computer just to create an inconsistent heat source.

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