Be Quiet! is a German manufacturer that mainly produces PC cases, power supply units (PSUs), and cooling-related products. As the company's name suggests, their products are designed with a particular emphasis on quiet operation. The company is no stranger to the North American markets, slowly but steadily increasing their presence over the past several years. They are, in fact, one of the few EU-based companies that managed to maintain a foothold in the North American market during the pandemic.

Looking at their overall product offerings, Be Quiet! is a fairly typical PC peripherals manufacturer. The company is perhaps best known for for their impressive lineup of PSUs, while they also offer cases, fans, and coolers as well. And these days, that of course extends into all-in-one (AIO) CPU liquid coolers as well, with their Pure Loop family of coolers.

True to their design ethos, Be Quiet! has built the Pure Loop series to operate with as little noise as is reasonably possible. And unlike some other players in this space, the company isn't trying to make the Pure Loop a niche, high-end (read: expensive) offering; so the coolers are competitively priced for the mass market. Overall, the Pure Loop series consists of four coolers, ranging from 120 mm and 240 mm in size up to 280 mm and 360 mm. All four coolers are, as is usually the case, practically identical with the exception of the radiator size.

For today’s review, we are taking a look at the 280 mm version of the Pure Loop AIO cooler, which is the second largest that the company offers, and anecdotally seems to be the most popular size for AIO coolers right now.

Packaging & Bundle

The Pure Loop cooler ships in a sturdy cardboard box that, alongside the custom internal inserts, provide excellent shipping protection. It is aesthetically dark and dim, much like nearly all of Be Quiet!’s product boxes, but with a wealth of information regarding the cooler to be found on the sides and rear of the box.

The items bundled alongside the Pure Loop cooler are fairly basic. Inside the box, we found the necessary socket mounting hardware, a small syringe with a little thermal grease, adapters for powering the fans, and a few cable ties.

The surprising addition here is a bottle of coolant, which is very rare for an AIO cooler. For as we will see in our technical breakdown, the Pure Loop is not a traditional sealed loop cooler, so users can manually replenish and replace its coolant.

The fans provided alongside the Pure Loop cooler are Be Quiet!’s own Pure Wings 2 PWM fans. As expected, two 140 mm fans are supplied with the 280 mm version that we are reviewing today. These fans have rifle bearings, which are remarkably quiet. They are the “high speed” version of the series, with a maximum speed of 1.600 RPM.

The Be Quiet! Pure Loop 280 mm AIO Cooler

The core design of the Pure Loop 280 mm AIO cooler looks fairly typical at first glace. Yet if you pay a bit more attention, there is a significant anomaly: the liquid pump is autonomous and not located on the main cooling block itself. The block merely serves as a heat exchanger between the CPU and the cooling liquid, with no moving parts at all.

Be Quiet! moved the liquid pump to up near the radiator, as an inline device. Although this probably bodes well for the longevity of the pump (as it is not directly exposed to very high temperatures) and it reduces the noise output by dampening its micro-vibrations, this approach also creates four more connection points. Typically, joints and other connection points are the weakest links in AIO cooler design, so the additional points here increase the chance for mechanical damage.

Be Quiet!’s engineers went with a very subtle and elegant design for the main block. The body of the block is mostly made out of plastic, supporting the copper contact plate. A decorative brushed aluminum overlay with the company’s logo covers the top of the assembly that has white LEDs subtly lighting its surround while the unit is powered.

The bottom of the main block assembly reveals a sizable octagonal copper block that is nickel-plated. Its finish is very smooth and free of imperfections. The block is large enough for most modern desktop processors, AMD's oversized Ryzen Threadripper excluded.

The radiator is a typical dual-pass cross-flow design, with tiny fins soldered on thin oblong tubes. At the bottom side of the radiator, there is one relatively large screw that serves as a filling port. Handling this requires care – the position of the screw forbids users from undoing it while the radiator is installed inside a system, or the cooler will drain into the system itself. The radiator needs to be placed such that the filling port is the highest point of the system, then undo the screw to add coolant. The series logo is printed on both sides of the radiator's frame.

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.

*noise levels above this are not suggested for daily use

Testing Results, Maximum Fan Speed

Our maximum speed testing is performed with both the fans and the pump of the kit powered via a 12V DC source. This input voltage should have the pump and fans matching the speed ratings of the manufacturer. The Pure Wings fans rotate a tiny bit faster than their specifications suggest, with our tachometer reading 1610 RPM. There was no difference between the two fans, suggesting great quality control – at least amongst the few samples that we tested.

The thermal performance charts show that the 280 mm version of the Be Quiet! Pure Loop performs on par with other similarly-sized solutions, without any significant surprises. The average thermal resistance of 0.0805 °C/W is good for a cooler with two 140 mm fans, matching the performance of most 280 mm coolers that we have tested to this date.

Although the Pure Loop 280 mm's thermals do not outperform most of the competition, it has a serious performance advantage comes to acoustics. With a reading of 37.9 dB(A), the 280 mm version of the Pure Loop is the quietest two-fan AIO cooler that we have ever tested. Still, 37.9 dB(A) is not an inaudible figure, so for users after especially quiet computing, they will probably not want to use their cooler at maximum speed for extended periods of time.

Testing Results, Low Fan Speed

Using a PWM voltage regulator, we reduced the speed of the fans manually down to half their rated speed, which is 800 RPM for the Pure Wings 140 mm fans. The pump was also connected to the same power source, functioning properly at this low-speed setting.

There are no significant changes in this test, with the Be Quiet! Pure Loop offering thermal performance analogous to that of other similar AIO coolers. It falls a little behind only when the load is very high, which harms the average thermal performance of the cooler a little, resulting in an average thermal permittance of 0.1066 °C/W. However, a closer look at the charts reveals that the Pure Loop performs admirably well when the thermal load is below 150 Watts under these operating conditions.

Much like before, the amount of noise coming off of the Be Quiet! Pure Loop is exceptionally low. With a noise output of 32.3 dB(A), the 280 mm version of the Pure Loop lands a better acoustic performance than that of most AIO coolers – even those with a single cooling fan. Even in the quiet October night, it is nearly dead silent under these operating conditions, audible only when someone gets very close to the cooler and in a completely quiet room.

Thermal Resistance VS Sound Pressure Level

During our thermal resistance vs. sound pressure level test, we maintain a steady 100W thermal load and assess the overall performance of the coolers by taking multiple temperature and sound pressure level readings within the operating range of the stock cooling fans. The result is a graph that depicts the absolute thermal resistance of the cooler in comparison to the noise generated. For both the sound pressure level and absolute thermal resistance readings, lower figures are better.

The graph reveals that the overall performance of the Be Quiet! Pure Loop 280 mm cooler falls between that of other similarly sized coolers. It generally is a little worse than the SilverStone Icegem 280 but a little better than the NZXT Z63 – a major win for Be Quiet!, considering the retail price of their cooler. However, from the graph, we can also see that the Be Quiet! Pure Loop 280 cannot reach very low thermal resistance figures regardless of its operating conditions, suggesting that it might not be an ideal solution for systems that may face extremely high thermal loads, even if only temporarily.

Conclusion

Be Quiet! designed the Pure Loop series to be a reflection of the company’s ideals – simple, subtle, effective, and focused on operating with the lowest possible levels of noise. From what we've seen during our testing the 280 mm version of the Pure Loop cooler, we conclude that the cooler has certainly lived up to those ideas, making for a major win for Be Quiet!.

The thermal performance of the Pure Loop 280 mm cooler is good, yet as you might expect for an acoustics-focused cooler, unexcitedly so. It does not do much better than most other AIO coolers, and many other products using two 140 mm fans tend to offer better thermal performance. As a matter of fact, even some 240 mm solutions can thermally outperform the 280 mm version of the Pure Loop.

However, when taking noise levels into consideration, the tables shift dramatically. The Pure Loop 280 delivered impressively low noise figures, making for the quietest two-fan cooler that we have ever tested here at AnandTech. And when we plotted that as part of a thermal resistance to sound pressure level chart, we could clearly see the Pure Loop 280 going head-on with products that cost twice or thrice as much.

Be Quiet! is a company that usually goes with subtle designs and the Pure Loop series are no exception. The Pure Loop 280 visually is very serious and elegant, based on clean, basic geometric shapes. It would probably look out of place in an extravagant PC with colorful RGB lighting all around it but it will definitely look great when the aesthetic theme needs to be clean and serious.

In conclusion, we find that the Be Quiet! Pure Loop 280 cooler is an excellent product. Even with the focus on keeping noise levels down, Be Quiet! hasn't left thermal performance behind, so the Pure Loop offers a very good balance between thermal performance and acoustics. And they're able to do all of this while keeping the price of the cooler quite reasonable (despite the ongoing pandemic), with the Pure Loop 280 easily found for less than $110. Taking in consideration both the cooler's performance and that low price tag, we can say that the Pure Loop 280 is a very good deal for users who want great overall cooler performance combined with an elegant appearance.