be quiet! Silent Loop 3 420mm review: magnificent mammoth

There are plenty of sayings about patience. Rome wasn’t built in a day, slow and steady wins the race, good things come to those who wait. If you ask me, be quiet! Silent Loop 3 proves these are all true, offering the first 420mm AIO cooler in the brand’s 23-year history.

It’s remained a bit of a gap for be quiet! as many of its PC cases support such large coolers. Silent Base 802, Dark Base Pro 901, and most recently Light Base 900 can all wiggle at least one 420mm radiator in, but you’d previously be forced into the arms of its rivals to saturate the space.

be quiet! Silent Loop 3 420mm

$174.90 / £125

Pros

• Pump is truly silent
• Refillable with extra coolant
• Gorgeous RGB
• Fantastic cooling
• Whisper quiet fans

Cons

• No 280mm model
• No white option
• Expensive

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How we test and review products.

Arriving just four years after its predecessor, be quiet! Silent Loop 3 is understandably a touch bigger at 457×140×52mm (L×W×H) to accommodate three 140mm fans. The pump carries an updated look, ditching the silver tones for a sleeker all-black frame. Similarly, the RGB lighting moves from a small accent to full-on centrepiece, carrying a similar sweeping fin arrangement as Light Loop, albeit in a vertical pattern.

Far from all style, it also packs plenty of substance. The copper-and-nickel-plated contact is significantly bigger, taking a rectangle approach rather than square to ensure complete coverage for longer Threadripper processors. As you might expect, be quiet! has also worked plenty magic under the hood with the aim to keep everything silent.

There’s a new six-pole motor with three phases and a three-chamber design to reduce noisy turbulences. Meanwhile, the pump features adjustable speed to ensure it’s silent even when cranked up to its maximum speed. I’m used to hearing the occasional glug or two from hardworking pumps, but Silent Loop 3 lives up to its name with nary a peep after hours of using it.

One of the biggest differences between Silent Loop 3 and its predecessor is that the new cooler comes bundled with up to three upgraded Silent Wings 4 high-speed fans. You might not notice a huge difference at first glance, as they still feature seven serrated blades and no RGB in sight, but the all-black aesthetic is a welcome change for uniformity.

Most of the magic happens under the hood with a new six-pole motor akin to the pump, fluid dynamic bearing design, and promises of greater versatility whether stuck to a radiator or pinned to the sides of your case. Rated for 30,000 hours, they’re built to last, but we naturally weren’t able to test the fans for such a period.

The four-pin PWM control offers fantastic versatility over its 1,900rpm speeds so you can balance noise with performance. At full pelt, you’ll see up to 78.4CFM of airflow and 2.36mmH₂O of air pressure. Admittedly, I’d have liked to see Silent Wings 4 Pro fans included with their optional higher ceiling, but the standard selection is more than enough and keeps costs at least $10 lower a pop.

As usual, be quiet! equips its AIO coolers with a refillable port so you can replace the fluid inside. You won’t need to use the included spare coolant for a good long while but it will come in handy as liquid naturally evaporates over time. This takes years and is only something you need to worry about when you notice performance degrade, but where you’d otherwise need to replace the device, you can simply give it a new lease on life with a quick pour.

Silent Loop 3 420mm is something we’ve been waiting for here at Club386, but it’s hard not to notice the lack of 280mm model to complement it. Silent Loop 2 catered to the form factor, which gave users the option to stick with 140mm fans throughout medium-sized cases. Your only options for now are to go for a chonkier chassis for larger fans or bite the bullet with 240mm and 360mm alternatives.

Similarly, the new range debuts without a 120mm option for small form factor (SFF) builds or white colour options. It’s possible be quiet! might eye up different sizes and colourways after the initial three debut on February 25, but what you see is what you get for the foreseeable.

No matter which you choose, you get a three-year warranty to keep everything in working order, but it’s the cost that will make or break it. Silent Loop 3 420 faces tough competition from Arctic Liquid Freezer III 420, yet its £124.99 / $174.90 asking price sits between £5 or $10 of its rival’s MSRP. The only wrench in the works is that alternatives have already come plummeting in price as low as £72 / $120.

Installation

The only thing missing in be quiet!’s assortment of accessories is an alcohol wipe to help clean used processors ready for installation. Otherwise, everything you need is in the box, including just enough thermal paste for a single application. I’m a big fan of pre-measured amounts, as it leaves little room for error, giving you peace of mind.

However, before we get to greasy part, you must first fix the right bracket for your CPU. Alongside the latest AMD AM5 and Intel LGA1851 processors, Silent Loop 3 also boasts compatibility with AM4, LGA1700, 1200, 1150, 1151, and 1155. Threadripper is also on the table, but only the larger 360mm and 420mm models offer the necessary frame given their penchant for higher temperatures.

Setting it all up is business as usual for our Intel Core i9-13900K. First, you secure the backplate with silicon washers and supplied standoffs, before slipping in the top and bottom mounting bars. Only then do you apply your paste in whichever fashion you see fit. We’re all about a central pea-sized blob surrounded by four smaller dots in each corner, but the sausage and single dollop methods are just as valid.

With the thermal conductive layer in place, clamp the block atop the CPU using thumbscrews. It’s one of the more painless coolers I’ve pieced together in recent years, lining up seamlessly.

Given the sheer size of a 420mm radiator, you won’t have many options to stow it away. A few cases allow a top mount, but front is a touch more common. So long as you keep the tubing higher than the pump, it’ll remain effective.

While there’s a level of convenience when fans come preinstalled to the radiator, not all builds are the same. I decided to go with a push configuration with my Silent Wings 4 on one side of the frame and the radiator on the other, which benefits from be quiet!’s traditional decoupled approach. There are enough screws to go any which way, however, including three more fans on the other side

Finally, plug in the 5V ARGB connector and you’ll soon witness your cooler come to life. Sat inside our test platform, it straddles the delicate balance of looking both professional with a stealthy black approach all while appealing to the gamer in me with gorgeous colourful lighting. It’s just a shame there’s no bleached version for white builds.

Performance

There are plenty of newer processors to choose from, but as both AMD and Intel shift focus to efficiency, Core i9-13900K remains one of the hotter-headed CPUs to test a cooler’s mettle. To see how performance scales under extreme load, we pit the chiller against Cinebench at 600, 1,200, and max RPM, which in this case reaches 1,900rpm.

Cinebench 2024

Core i9-13900K tops out at 253W, but this is a particularly difficult power draw to maintain for a prolonged period. The primary aim here is to see how it handles thermal throttling. Generally speaking, Silent Loop 3 420 scales well, but does see a noticeable drop at 600rpm relative to its maximum RPM.

Cinebench R23 scores

It’s not worth taking Cinebench R23 as gospel, as it’s susceptible to the room temps, air pressure, and humidity of any given day. That said, it provides a good point of comparison, and Silent Loop 3 420 performance is up there with the greatest.

Noise levels

Cranked up all the way to 1,900RPM, which is identical to Arctic’s included blowers, the fans are distinctly noticeable but not as intrusive as you’d imagine. As tempting as the inaudible 600RPM is with our sound meter struggling to read the lightest of hums, it’s likely not worth the performance trade for most, but nice to have the option regardless.

I’d opt for 1,200RPM or thereabouts because it sees very little performance drop-off in exchange for a near-silent operation with no unpredictable signal noises offending the ear. This is the beauty of three 140mm fans working in tandem, pushing significant amounts of air without the sound sanction.

Overall, be quiet! offers the most silent cooler we’ve tested yet, undercutting rivals by up to 16%. That’s no small feat.

Temperatures

More than half the time, be quiet! Silent Loop 3 beats its closest competitor in temperatures, with the largest gap spanning an entire 5°C. Admittedly, it fares better at more sustainable wattages, which is more representative of your everyday anyway.

With less than a degree between max RPM and 1,200RPM, it’s worth the drop just to make your setup 5dBA quieter, but you’ll always have the higher speeds ready and waiting for more extreme workloads.

Conclusion

Silent Loop 3 proves a worthy upgrade from its predecessor, from all its tweaks under the hood to its bright and beautiful contemporary appearance, giving a much-needed coat of paint to the dated Silent Loop 2. While I’ll still pine for a white model, the stealthy matte black approach fits in most rigs with just the RGB-clad waterblock drawing your eye to the heart of your PC.

There’s no doubt in my mind that be quiet! Silent Loop 3 is the best CPU cooler to pass through Club386 halls, setting the bar for 2025. It comes complete with some of the lowest temperatures we’ve seen and couldn’t be quieter, living up to its promises of total silence.

Performance alone justifies the loftier price tag, but there’s still a question of value as long as Arctic Liquid Freezer III exists. Factoring in current discounts, be quiet!’s solution costs up to 74% more than its rival in the 420mm arena. The refillable port and extra coolant go some ways to justifying the extra, but only you can judge whether it’s worth paying for the best.