The Be Quiet! Dark Rock Pro 5 CPU Cooler Review: When Less Is More
by E. Fylladitakis on January 16, 2024 10:00 AM EST- Posted in
- Cases/Cooling/PSUs
- be quiet!
- CPU cooler
- Air Cooling
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
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Footman36 - Tuesday, January 16, 2024 - link
Appreciate the review. $80 is still ridiculously expensive for a HSF when you can buy the Thermalright Phantom Spirit for $33 and get similar performance. I would like to see a review of this HSF on Anandtech.PeachNCream - Sunday, January 21, 2024 - link
I get and support where you're coming from. A good condition used laptop can sink you for under $200 (new laptops start at around that price as well though adequate future proofing is more or less a $400 laptop) and for your $80 here you get a single component that doesn't compute anything on its own that you have to be bothered to put together yourself. What a waste! But also, in fairness, that DIY segment is collapsing as we learn we can just use a phone we already own or carry our computer anywhere in the form of a power-efficient and inexpensive laptop so prices relative to inflation have fallen a bit lately so $80 isn't all that bad these days. Still though, I agree with you that it's an utterly stupid venture to go purchasing an overpriced, non-movable desktop PC more than 20 years in to this century and most of the world agrees if you look at sales of hardware.RLees - Sunday, January 21, 2024 - link
Well, perhaps true for your use case -- but you'll pry my fixed gaming PC out of my cold dead hands.Sure I =could= get a laptop with an external GPU but when I looked at that I ended up with a very large laptop with all kinds of luggability issues -- so stayed with my desktop and thin/light laptop solution with no compromises for either use case.
PeachNCream - Sunday, January 21, 2024 - link
Gaming laptop? Those are a huge waste of money and effort as well. There really is no need for a dGPU of any sort if you use a bit of selectivity in the types of things you use your computer for although, I do understand a lot of people don't know any better and are sedentary being a computer screen for a substantial number of hours of their lives. I hope you can find other ways to have fun someday.nubie - Tuesday, January 16, 2024 - link
How does this compare to a budget cooler like the 7-pipe Phantom Spirit? At half the price I am willing to bet it is still swinging. You could upgrade to Noctua fans and still be in the same ballpark for noise and performance. I suppose the looks are "pedestrian", but I don't drive a bro-dozer either.mode_13h - Thursday, January 18, 2024 - link
Thank you for including the Noctua NH-C14S in your testing. Since I like downdraft coolers, I appreciate having more data on it and how it compares to other popular models.krazyfrog - Friday, January 19, 2024 - link
I'm not sure I get the point of an arbitrary 50% value for the low fan speed test when all models are going to be at different RPM and noise levels. What exactly is so special about the 50% value for it to be the normalization constant? Why not noise normalize instead at a steady decibel level?E.Fyll - Saturday, January 20, 2024 - link
Much like you said, it is an arbitrary point, showing the capacity of the cooler at low airflow.We are doing far better than "normalizing" at a single dB level. Instead, we take measurements at several levels and compose the TRvsSPL chart. It shows the capacity of every cooler across its entire operational range and how airflow affects its performance (slope). If I were, for example, to set a "standard" dB level, there would undoubtedly be cases where the cooler would not be able to operate there at all. Check this review's chart for example. If I chose 33 dB(A) as the "normalized level", the Dark Rock Elite would not be able to reach it. If I chose 36 dB(A), the NH-U12S could not reach that. There would be chaos across the reviews. It would be far easier and faster for me to test a single point rather than taking multiple measurements and generating the graph but that is just bad practice.
RLees - Sunday, January 21, 2024 - link
The 1st image on the last page appears to be the Dark Rock Pro 4 cooler, not 5.Correct?
Ryan Smith - Monday, January 22, 2024 - link
No, that is the DRP 5. All of these photos were taken at the same time. (Plus we don't even have a DRP 4)