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
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  • Alistair - Thursday, October 14, 2021 - link

    I didn't read any clear distinction between pump noise and fan noise. Is the pump especially nice sounding or quiet also? Or just the fans run slower than the Corsair one, if so, Corsair is still a great option as long as the Corsair pump is quiet. Reply
  • Tom Sunday - Thursday, October 14, 2021 - link

    Be Quiet is a fine company out of the Hamburg area in North Germany. Great to see the Germans now producing more high-quality goods for sale in the U.S and in the PC hobbyist world. I would most certainly buy from 'be-quiet' first and not Corsair who is satisfying their investors with mostly cheaper China goods all to making a bigger buck and over-marketing their products. As to cooling, the AIO market has always been way overpriced and much overrated; their pumps have never been perfected after all this time. And do I really care if my PC runs 10 degrees hotter? My Noctua D15 has been with me now for 10-years and straddled three completely new system builds. No downtime. I am now ready for Alder Lake with a Z690 Asus Hero MB, DDR5 and stuffed into a EATX. No doubt the 'be quiet' Dark Rock TF2 is on the bill and in 2022 my first cooler replacement in 11-years. Greetings from Stehekin, WA where you have to make things count! Reply
  • Oxford Guy - Friday, October 15, 2021 - link

    My Corsair H50 exploded, destroying a video card and making a huge mess. Somehow the motherboard survived. Reply
  • COtech - Sunday, October 24, 2021 - link

    These Be Quiet coolers are made in China just like the Corsair ones. Reply
  • Purpose - Friday, October 15, 2021 - link

    This is a U-Flow radiator, not cross flow. Reply
  • docbones - Friday, October 15, 2021 - link

    Would love to see how it compares to the Ice Giant. (for noise and cooling) Reply
  • SuperMover - Saturday, October 16, 2021 - link

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  • Jasonovich - Monday, October 18, 2021 - link

    Be Quiet! Pure Loop 280 cooler looks aesthetically pleasing but where's the RGB. Not asking disco but customised cases have to look good looking into the window.
    Off the subject, Noctua the pinnacle manufacturers of coolers, why don't they do AIO?
    Reply
  • ltkAlpha - Tuesday, October 19, 2021 - link

    A must-have feature that I'm looking for in AIOs is the ability to link fan speed to water temperature, as you don't need to hear the fans spin up over every load spike - they do so very gradually with load. I would go so far as to say that with AIOs, for the vast majority of people, that's the key differentiating feature of water cooling. Unfortunately most reviewers completely ignore the presence of the feature (curiously, many of the brands don't actively market the feature either), so benchmark results end up being of limited usefulness to me, since a) I don't care how an AIO sounds @100% fan speed - I want to know how loud they are when temperatures stabilize at a given CPU wattage and b) I don't care about half of the products presented, so to me the comparisons are apples to oranges. Reply
  • Keljian - Saturday, December 4, 2021 - link

    There are two brands that I know of that have this feature, Corsair and nxzt. Interestingly though the fluctuation in temperature of coolant (the band of high/low) is not big, maybe 20C or so.

    I actually have a thermal probe on the top fin of my D15 and the max temp when the cpu is going ballistic is about 35C or so at 20C ambient. The cpu (overclocked) however is up around 80C. I have found that having the fan ramp up for more airflow doesn’t actually make a huge difference to the temp either, some airflow is good, but it caps out pretty quickly.
    Reply

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