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 Dark Rock Pro 5 Testing Results
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  • peevee - Tuesday, January 16, 2024 - link

    Who could recommend a good air cooler for AMD 7950x, not overpriced?
  • meacupla - Tuesday, January 16, 2024 - link

    For a 7950X?
    Noctua D15, or get a 280mm or 360mm AIO CLC.
  • peevee - Thursday, January 18, 2024 - link

    D15 is quite expensive (and I do not see TDP Wattage spec anywhere), CLC is not air cooler I have asked for.
  • StevoLincolnite - Friday, January 19, 2024 - link

    Good thing we generally don't care what you asked for.

    But a 280mm/360mm is probably the best bang for buck you can get either way.
  • meacupla - Friday, January 19, 2024 - link

  • Googer - Monday, January 22, 2024 - link

    I am using the Noctua D15 with a 7800 and Noctua's optional AMD offset kit for better performance. I am able to hit and sustain boost speeds with no problems.
  • nubie - Tuesday, January 16, 2024 - link

    Thermalright Phantom Spirit SE 7-pipes is like $35. Should cool 230w (Stock 7950x under load).
  • peevee - Thursday, January 18, 2024 - link

    Thanks. I looked at Microcenter and saw almost $100 coolers which are only rated for 150 W (on the box), not even enough for 170 W TDP, and somewhat cheaper coolers without Watt ratings but with similar CFM (after all that is what matters, right?).

    That Thermalright Spirit 120 SE says 105W BTW, I doubt it is good for 170W TDP CPU.
  • usiname - Friday, January 19, 2024 - link

    The rated TDP is tested diferently by all manufacturers so the only option is to watch reviews, TechPowerUp have good comparison on Ryzen 7900x.
  • IlllI - Friday, February 2, 2024 - link

    Hmm maybe Scythe Fuma 3...? I see it on amazon for $50

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