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 Alphacool Eisbaer 240 CPU Liquid Cooler Testing Results, Maximum Fan Speed (12 Volts)
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  • Sushisamurai - Sunday, August 7, 2016 - link

    I think mainstream computers/CPU's don't need liquid, at all. If you're running an enthusiast build/HEDT then I think it's almost necessary. My CPU draws almost 230W at full load - I didn't bother putting an air cooler for noise issues.
  • rhysiam - Monday, August 1, 2016 - link

    "I personally think that air coolers have reached their EOL. There is no need for a big chunk of metal to sit on top of your motherboard especially when nowadays you can buy an excellent AIO that is reasonably priced, quiet, cools better, and looks aesthetically more pleasing, and its painless to install"

    I can't agree with you at all on this. If we consider the three key metrics we can quantify being price, noise and thermal performance; air coolers objectively beat AIO water coolers by a significant margin. Entry level water coolers like the H60 are more expensive, hotter and louder than a wide range of air coolers, and perform terribly compared to similarly priced air towers (H60 prices take you into mid-range air cooler territory). Once you move up a tier to high end air coolers like the NH-D15, you need to spend far more money to get a similarly performing AIO. There are 240mm closed loop water coolers that appear to offer superior thermals for close to the $100 mark, but they do so by using hair-dryer like fans. If you want D15 performance from water and care at all about noise levels, you need to be prepared to spend a lot of money.

    There are absolutely benefits to AIO water coolers: stress-free portability, RAM compatibility and potential to use in smaller cases. But, if you care primarily about getting the highest performing and quietest CPU cooler for your dollar, air still wins every time.
  • Hxx - Tuesday, August 2, 2016 - link

    I bought an H55 for $25, an H110 for $55, and H100i gtx for $75, a thermaltake water 2.0 performer for $20, a thermaltake 240mm water 2.0 for about $50...over the past 4 or so years. Yes not everyday prices, but newegg sales, microcenter open boxes, etc. Like I said, no need for an air cooler anymore. Corsair even goes as far as covering your components if your cooler for whatever reason breaks and takes some other components with it.
    The latest cooler I bought is the corsair h100i gtx for $75. My overclocked core i7 4770k 4.6ghz sits at 25C and 40ish when gaming in a corsair air 240 case. The pump is in "quiet mode". I can't hear the fans or the pump so I m happy. Also $75 is not a lot of money for a CPU cooler when a high end air cooler is almost just as much.
  • ikjadoon - Tuesday, August 2, 2016 - link

    Wrong. You need to update to Gen5 Asetek.

    http://www.hardocp.com/article/2016/02/11/arctic_c...

    $25 cheaper than the NH-D15, quieter than the NH-U14S, and 5C cooler than the NH-U14S.

    Keep up with reviews, dude.
  • rhysiam - Wednesday, August 3, 2016 - link

    So this Eteknix review paints quite a different picture of that cooler you linked: http://www.eteknix.com/arctic-liquid-freezer-120-a...
    A full 14 degrees hotter than the D15 on an OC'd CPU (3570K) at 1.35V. Acoustics are still great, but temps, while fine, are hardly world beating. In fact they suggest 1.35V on an i5 is asking a bit too much of this 120mm cooler.

    My issue with the HardOCP review is that the biggest load they put that cooler under is a 4.4Ghz OC on a 4770K at a measly 1.25V. That's just not enough to push any half decent cooler. Obviously it's got a great price and is really quiet, so would be a good choice for lots of people looking for a mild OC, but if all you want is a 1.25V mild OC, another valid option would be a cheap air cooler for $25?

    I'm not saying AIO coolers don't have a place, clearly they do. But to say they make air coolers "EOL" is just not accurate IMHO.

    Also, maybe ditch the BM next time? I expect better from comments here at Anandtech.
  • letmepicyou - Monday, August 1, 2016 - link

    What you're missing about water cooling might be the fact that water cooling setups are WAY more convenient than some of the better air solutions out there. I can show you a nook in my one cupboard where I have some of the best air coolers around (Tuniq Tower, Antec CNPS 10X, Thermalright Silver Arrow, the list goes on). The problem with air? First is the weight it puts on the motherboard (which is a particular concern if you move your computer regularly). Second is the fact many high-end air coolers interfere with the ram slots, depending on the cooler / motherboard combo you happen to be using, and whether or not your ram happens to have taller than average heat sinks.

    The perfect solution? An AIW water cooling setup. There is no motherboard stress worth mentioning, and I have GOBS of clearance for literally any ram I choose to use, regardless of where or how it's oriented on the board. I have a pretty stout system (i7 4790k, stock clocks) but it's not always about overclocking ability or raw cooling potential, sometimes it's about pure logistics.
  • rhysiam - Tuesday, August 2, 2016 - link

    While water may be more convenient, it's also more expensive for a similar performance tier. And it's not like low profile RAM is hard to find or has any real drawbacks. Air certainly puts more weight on the motherboard, but it doesn't introduce liquid to the system. So while water is likely safer for a portable system, I'd suggest air is the safer bet for a static PC.

    Clearly you'd prefer to spend more or sacrifice cooling performance for system portability and RAM compatibility... that's fine, there's heaps of situations where that's the right call. But there's undoubtedly a place on the market for the superior performance per dollar that air coolers offer.
  • retrospooty - Tuesday, August 2, 2016 - link

    " Second is the fact many high-end air coolers interfere with the ram slots, depending on the cooler / motherboard combo you happen to be using"
    - You may have a point if you are upgrading an older system and therefore stuck with particular existing parts, but if you are building a new system you can build a better cooled system for cheaper with a good air cooler.
  • zodiacfml - Tuesday, August 2, 2016 - link

    That gave me an idea for a future build. I guess, water cooling should be focusing on graphics these days.
  • ikjadoon - Tuesday, August 2, 2016 - link

    Yup. I'm slapping this AIO CLC on my next GPU: cheaper than NH-U14S, cooler than a NH-U14S, and quieter than a NH-U14S--all at the same time! :D

    The reign of air coolers is about to end with Gen5 Asetek.

    http://www.hardocp.com/article/2016/02/11/arctic_c...

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