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 only manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being acquired 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

The EKWB EK-XLC Predator 240 Testing results, maximum fan speed (12 Volts)
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  • zeeBomb - Tuesday, December 15, 2015 - link

    Awesome cooler
  • HollyDOL - Tuesday, December 15, 2015 - link

    So, with a SkyLake, you can cool at about 10°C above ambient at 35dB? That's definitely NOT BAD outcome.
  • DanNeely - Tuesday, December 15, 2015 - link

    Almost certainly not; you'll see temps significantly higher. The heater blocks E. Fylladitakis uses to simulate a thermal load that's more stable than you can get with a real CPU have a major failing that makes them impossible to equate to performance on an actual system useless. The temperature reported on your CPU comes from a handful of tiny hotspots on the die that do a lot more work, consume the majority of the power, and are much hotter than the rest of the die.

    The hot spots are why, although TDPs have stayed more or less fixed on desktop chips since the Core 2 era, actual CPU temperatures have been on a steady upward swing. Each new process shrinks the bits of the CPU that do the actual calculations and generate the largest part of the heat into a smaller chunk of the die. The extra die space gets filled up with cache which doesn't have hot spots or GPU space that because they have large numbers of tiny cores instead of a few big ones can spread out the heat a lot better.
  • DanNeely - Tuesday, December 15, 2015 - link

    The CPU waterblock in this kit looks a lot like the EK Supremacy EVO in my custom loop. That block is explicitly intended to be taken apart and reassembled prior to installation (it has several parts intended to control water flow that are intended to be swapped for different CPU models), Unless you're an idiot who can't be bothered to read directions it was strait forward to follow the printed instructions to open it up, swap in the parts for my CPU and then put it back together.

    That experience also has me concerned about your testing methodologies results will correlate to real world relative performance. The intent of adjusting all of those fiddly bits in the block was to direct the flow to maximize cooling of the hottest parts of each specific chip; something that can't be captured by a simple resistive heating block. Testing I saw a few people who were curious if it really mattered showed spreads between different internal configurations of several degrees; comparable to the total spreads you're seeing among decent water cooler kits.
  • londiste - Tuesday, December 15, 2015 - link

    The extra header on the fan controller is with Predator 360 in mind.
  • tabascosauz - Tuesday, December 15, 2015 - link

    This entire article was written with the assumption that the only benefit offered by the Predator is its expandability, as with the H220-X. That's not the point of the kit.

    The point is that when you buy the Predator, you are basically buying EK products, with the added benefit that someone has already assembled the parts for you. The CPU block is the same Supremacy (EVO?) block that you get off of the market for your custom loop, and so are the Vardar F4 fans and the Coolstream PE rad.

    It's not meant to be an end to the endless CoolIT and Asetek AIOs on the market. People aren't going to buy it in comparison to the H100i. They'll buy because it's a nice place to start one's future custom loop system.
  • tabascosauz - Tuesday, December 15, 2015 - link

    I suppose I'm expecting a bit too much from AT reviewers these days. Clearly, they don't do even the slightest bit of reading before starting their reviewers. Block appears to be small and doesn't have a pump like other AIOs? A bit of digging even into EK's product page for the 240 would reveal that the block is a Supremacy MX and obviously wouldn't have a pump integrated into it, like all proper watercooling CPU blocks (exception made to the Apogee Drive II).
  • forgot2yield28 - Tuesday, December 15, 2015 - link

    Your first sentence states that the point is not expandability, and yet your last sentence states that it will be purchased as a start to a future custom loop--ie users will add and modify it, in other words, expanding it. Did I miss something?
  • tabascosauz - Tuesday, December 15, 2015 - link

    Ach, never mind. The review is adequate.
  • owan - Wednesday, December 16, 2015 - link

    Yea, you missed the fact that its *not only* expandability. There are other products that offer expandability, but EK's offers expandability and quality components you'd probably be happy re-using.

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