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, with the ability to vary the load, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it were 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 very 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 or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60W and 340W, in 2W 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 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, we're measuring these manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is acquired via a laser tachometer. The fans (and pumps, when applicable) are powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1m 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.

Noise Level Reference Values
<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper)
38-40dB(A) Quiet (slight humming)
40-44dB(A) Normal (humming noise, comfortable level)
44-47dB(A) Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (level equivalent to a ≈1500W vacuum cleaner)
>54dB(A) * Intolerable for home/office use; special applications only.

* Noise levels above this are not suggested for daily use

Silverstone Testing Results, Maximum Fan Speed (12V)
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  • piroroadkill - Wednesday, February 12, 2014 - link

    This is great, but where's at least a couple of air coolers in there for reference?
    I'd recommend the ever popular and classic Noctua NH-D14 since it's a widely reviewed, well known reference point.
    Reply
  • piroroadkill - Wednesday, February 12, 2014 - link

    If only I could edit my reply. I see that there is a category in Bench for CPU coolers. Never mind! Reply
  • ddriver - Wednesday, February 12, 2014 - link

    It would still be a good idea to include a few high performance air coolers to compare how they do against the low end h2o coolers. Reply
  • just4U - Thursday, February 13, 2014 - link

    Or even a Coolermaster 212 which is pretty much the go-to HSF for standard builds due to cost/cooling performance. Reply
  • MrSpadge - Wednesday, February 12, 2014 - link

    Agreed - one standard high performance air cooler for ~50€ would suffice, but not including any feels incomplete. Reply
  • jmke - Wednesday, February 12, 2014 - link

    so true, would have been a very good idea to throw in a €20 and €50 air cooler, using one of the 120mm fans to see how these water coolers compare. Reply
  • jmke - Wednesday, February 12, 2014 - link

    best performance/noise CPU coolers is the Noctua in their charts. One of the best AIO is the NZXT Kraken X60. Let's see how they stack up:

    Noctua NH-U14S (2 Fans 100%) 43.1°C / 33.3 dBA / €70
    NZXT Kraken X60 (Silent) 41.2°C / 30.5 dBA / €140

    is a few °C difference worth an extra €70? is a HSF worth €70?
    how important is CPU temperature?
    if you don't overclock, keeping CPU temp below max would suffice...
    Reply
  • mr_tawan - Wednesday, February 12, 2014 - link

    Personally I use closed-loop water cooler(corsair H60) because the large air cooler I used (CM Hyper212) gets in the way of ram modules (people with intel chip does not suffer from this, AFAIK). With water cooler, I can put 4 DIMM on the mainboard without any problems.

    In my system, there is no significant differences between these two cooler. Water cooler is a little bit louder, btw.
    Reply
  • Idonno - Saturday, December 06, 2014 - link

    I agree 100%. Plus the sheer weight (on the MB and CPU) and size that an air cooler like the Noctua NH-U14S has to be to be even remotely competitive is absolutely ridiculous.

    It's not just the better temps that closed loop water coolers provide, it's convenience, accessibility, less strain on critical components and better temps.

    All-in-all the higher cost of closed loop water coolers is IMO worth every penny.
    Reply
  • E.Fyll - Wednesday, February 12, 2014 - link

    Unfortunately, the few air coolers that I still have in my house are outdated. Yet, there will be many air cooler reviews and roundups coming in the near future, with their results directly comparable to those of this review. :) Reply

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