Performance Analysis

With a relatively slow fan speed, modest heatsink size, and a single fan in play, we weren't expecting miracles here, but the Dark Rock Slim managed a reasonable 45°C delta T in out LGA 1151 system, which actually beat the larger Dark Rock 4, likely thanks to a faster-spinning fan. As you can imagine, the cooler was inaudible outside of our test case and even with our ear close to it, there was just a gentle airflow noise.

Sadly, the cooler wasn't beefy enough to handle our overclocked Core i9-7980XE (165W at stock, but higher when overclocked), but Be Quiet! does stipulate a maximum 180W TDP, so that's not surprising. You'd need something larger and with more airflow here, as no amount of efficiency is going to make up for modest airflow with a monster CPU such as this. 

Our Ryzen 7 1800X isn't exactly an easy customer either, and the delta T of 56°C is again reasonable for an air cooler and better than the Dark Rock 4 and Arctic Freezer 33 eSports One. Interestingly, it was also cooler than the Corsair H115i Pro RGB and H150i Pro RGB on their Quiet profile settings, and to our ears the Be Quiet! cooler made less noise too. There are gains to be had elsewhere if you lean more towards cooling prowess, though, as the Noctua NH-U12A offered a 7°C drop in the AMD system while the Corsair H100i RGB Platinum was a sizeable 11°C cooler.

Conclusion

With its focus clearly on mainstream CPUs and also low noise, the Dark Rock Slim performed well compared to the competition in our Socket AM4 and LGA 1151 systems, outstripping the cheaper Arctic Freezer 33 eSports One and even giving some AIO coolers a run for their money at lower noise levels and fan speeds. However, that's where its comfort zone ends, because as super-quiet as its fan is, it doesn't work miracles and simply can't shift enough air to match more powerful coolers or deal comfortably with overclocked HEDT CPUs. Noctua's NH-U12A proves to be far better too, but it's louder and more considerably more expensive, so Be Quiet! is safe on that note.

This isn't necessarily that evident with our quad-core Intel system, but it's a different story with our overclocked eight-core Ryzen CPU. As such, if you're after a super-quiet and attractive no-fuss cooler for a stock-speed six-core CPU or overclocked quad-core CPU, then it gets our vote - it's pure bliss if you have sensitive ears. Above this, though, its cooling to noise ratio quickly becomes far less appealing.