Top Tier CPU Air Coolers Q3 2015: 9-Way Roundup Review
by E. Fylladitakis on July 6, 2015 8:00 AM ESTTesting 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
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Pissedoffyouth - Monday, July 6, 2015 - link
I wonder how a D15 or similar, with the fans removed, would work with a 45w or 65w APU to make a passively cooled PC.ImSpartacus - Monday, July 6, 2015 - link
That's a really interesting consideration.MrSpadge - Monday, July 6, 2015 - link
This will depend greatly on your case airflow. And if you only run short load bursts (browsing etc.) which can easily be absorbed by the heatsink heat capacity or continous loads (games, work), where the exchange of heat from the heatsink to the outside world limits cooling.iamezza - Tuesday, July 7, 2015 - link
With good fan control you could set the fan to switch off below a certain temp. So it could be silent 99% of the time but with a low rpm fan there if needed.Mumrik - Tuesday, July 7, 2015 - link
You'd probably still need some level of airflow.I've never had a fan on my Scythe Ninja that cools an i5-2500k. I think that's a 95W TDP.
It's close to the single 12cm rear exhaust though.
Beany2013 - Wednesday, July 8, 2015 - link
I did similar with my old SLACR Q6600 95w CPU - Noctua D14 (I think) with a fan on a controller. At stock speeds (with a pair of Noctua case fans on it) it had just enough airflow to run without the CPU fan running at all. When I wanted performance, I could overclock from 2.4ghz to 3.something ghz (I can't remember but I think they went to 3.6ghz?) and just turn the CPU fan up to 'normal' speeds and it'd never get above 70deg and it was still a very quiet machine - HDD noise was far more noticeable than fan noise.I really must get some decent fans for my current rig - a slightly long-in-the-tooth A8-3870 mit 16gb RAM that is still running the OEM cooler. Yes, I've got bored of overclocking. I still have that noctua kit kicking around somewhere, really must dig it out and see if I can get an adapter for it. I'm sure that'll tide me over till we see if Zen is worth a light...?
Essayjedii - Friday, July 10, 2015 - link
I have made a post about D15 in here <a href="http://www.dumblittleman.com/2015/04/14-problems-f... Hope ou find it interesting and useful.Essayjedii - Friday, July 10, 2015 - link
I have made a post about D15 in here http://www.dumblittleman.com/2015/04/14-problems-f...Hope ou find it interesting and useful.
Haravikk - Sunday, July 12, 2015 - link
My current machine is an i7-4790T (45W, 2.7ghz, quad-core, hyper-threaded, 3.9ghz turbo with HD4600 graphics) in an Akasa Euler case, which means the case acts as a heat-sink. As I type this I'm transcoding video on all eight hardware threads with a total load of about 760% (where 800% is max), at a CPU temperature of 85ºC and a clock speed of 2.97ghz.Of course that's for a passive case rather than a heat-sink on its own, but as long as you have somewhere for that heat to go it definitely seems doable. For example if you used an open-air case then ought to just rise out between the heatsink fins so airflow may not be required at all.
Basically keeping the case from becoming a big box of hot air is crucial; the Euler case with my processor (which is a slightly higher TDP than the 35W that the case recommends) gets pretty hot internally, which isn't great for internal drives. I ended up having to swap an mSATA SSD for a 2.5" one, as the mSATA drive just got too hot, while the 2.5" one has a bigger surface area and a metal body. Even so, I squeezed a tiny 40mm fan inside just to help pull hot air out on warmer days.
So ehm… yeah, possible, but you have to be sure you've considered where that heat is going to go before you attempt it. But as others have said; if your case has room then you should just put fans in there anyway and set them to switch off at lower temperatures; you can also use very slow, quiet fans so even if they do run they're silent.
Oxford Guy - Tuesday, July 14, 2015 - link
Stick with a cooler like the NoFan models which are made specifically passive cooling. They will be much more effective.