Thank you be quiet! for sending us this CPU cooler to review!

Lately, we've been blessed to be able to review several of be quiet!'s products. This includes CPU coolers and PC cases. I reviewed the large and luxurious Light Base 900 FX, a case that exceeded my expectations in spaciousness and cooling performance, while keeping the sound levels way, way down.  That case, being as large as it is, supports multiple radiators, up to 420mm in size, for the best in CPU cooling (outside of custom loops). I had originally installed the already great Pure Loop 2 FX 360mm cooler from be quiet! that I absolutely raved about - it lowered temperatures and sound levels so much that I was absolutely floored. I didn't think it could get much better - until be quiet! sent us this 420mm cooler to review. As good as the old one is, the performance on offer here really surprised me.

The be quiet! Silent Loop 3 420mm is the largest water cooling all-in-one (AIO) kit that be quiet! currently sells, and is at parity in radiator size with most of the competitions' largest. Actually, many cooler makers skip the 420mm size entirely, because it takes up so much space inside of a case that not all cases can fit one. However, the surface area of a 420mm radiator (420mm x 140mm) is significantly larger than a 360mm (360mm x 120mm) - over one third more! This leads to a radiator that can handle significantly more thermal energy before heating up, leading to overall much lower fan speeds necessary to get rid of that heat. Larger fans means less sound generated and more airflow at the same speed, so using 140mm fans has that added benefit as well.

It's funny because while writing this review, I had turned on Prime95, a well-known CPU burn-in tool, to see how long it would take for this cooler to heat up past 80C, a temperature that the Pure Loop 2 FX 360mm would reach within ten minutes. I ended up missing that moment (and I forgot to log), but what I did find funny is that it took almost a full hour to hit 85C - and for just a quick moment, perhaps a couple of seconds, I actually heard my PC. The CPU fans spun up for just a couple of seconds, the temps quickly dropped to the 60s, and then my system was dead silent again. This massive radiator is seriously impressive. I was shocked that just a couple seconds of high speed on the fans dropped the temps so much so quickly.

Of course an AIO water cooler is more than just a radiator. The primary part is of course the liquid that carries the heat to the radiator, the pump that keeps the water moving, the fans that keeps the radiator cool, and the CPU block that is in contact with the CPU to take the heat from. Of course there are tubes to link it all together. All-in-one water coolers are sealed systems that have everything integrated, so users don't have to think about any of that; they just put the CPU block onto the CPU with some thermal compound, mount the radiator to the case, mount some fans to the radiator, make sure that the CPU fans and pump are connected to power, and off they go.

Speaking of sealed, be quiet! has one feature on their water coolers that makes them one of the best out there (in my opinion). That feature is the ability to refill your coolant with a convenient fill port. Not only that, but they include additional liquid coolant in the box! Since most affordable water coolers use copper for the CPU plate and aluminum for the radiator, pure distilled water cannot be used. It's a mixture of water and propylene glycol. Without the mixture, copper and aluminum will react, breaking down both. Most coolers of this type use a similar liquid, but very few include more in the box.

One of the major upgrades for this new Silent Loop 3 over other models is the new CPU plate. It uses copper with nickel plating, making it safe to use with liquid metal thermal interface compound. But the main upgrade is that it's a longer, more rectangular plate compared to older models like the Pure Loop 2 FX, which allows it to be used with larger CPUs including AMD's Threadripper. It's also better for existing CPUs, as it should better spread heat since with modern chiplet designs, the heat generation is focused in multiple areas. As good as my results were with the old cooler, this one works dramatically better, and the CPU plate is likely responsible along with that massive radiator.

The performance of a cooler like this really comes down to two things: temperatures and sound pressure level, or SPL. Since there is not one tool to record and measure both (at least not that I'm aware of), I recorded temperatures using hwinfo64, and kept an eyes on my classic Radio Shack Digital Sound Level Meter. I mounted it on a tripod, and put it about one foot from the side glass panel, at about top of the case height. I used a similar method for measurements when I did the Light Base 900 FX case review, so I had to reuse some of those measurements here. (Full disclosure: I took a new set of measurements but they were lost accidentally.) For all testing I used Arctic Cooling MX-6 thermal compound. Since I measured the old cooler with my old paste application, I installed the new cooler and used it for a few weeks before testing and measurements to avoid any 'brand new paste' issues with the results. I can also say that having lived with it for a while, it's been perfect with no issues.

Here are my results comparing the be quiet! Pure Loop 2 FX 360mm with the be quiet! Silent Loop 3 420mm, all with MX-6 thermal paste:

Prime95 + Furmark 2 for ten minutes:

be quiet! Pure Loop 2 FX 360mm:
Max CPU Package Power: 209W
Max Core Temperature Average: 74C
SPL Level in dB: 46dB most of the time, with ramps up to 51dB

be quiet! Silent Loop 3 420mm:
Max CPU Package Power: 210W
Max Core Temperature Average: 66C
SPL Level in dB: 44dB most of the time, with ramps up to 48dB

As you can see, the Silent Loop 3 420mm stomped all over the already impressive results, with a solid eight degree drop. It's also a 2-3dB quieter all of the time, with even peaks being a lot lower, which surprised me, as I had assumed most of the loudness came from my GPU ramping up. Whatever the case, this leads to slightly better performance, as we'll see with the Cinebench R23 results below:

Cinebench R23 for ten minutes:

be quiet! Pure Loop 2 FX 360mm:
Max CPU Package Power: 181W
Max Core Temperature Average: 65C
SPL Level in dB: 40-41dB
Cinebench Score: 27271

be quiet! Silent Loop 3 420mm:
Max CPU Package Power: 203W
Max Core Temperature Average: 63C
SPL Level in dB: 38-40dB
Cinebench Score: 28391

This pattern of slightly better SPL levels and temperatures, along with slightly higher scores also carried through to 3DMark Time Spy. I don't have full data compared to the other tests, but the sound levels are about 4dB quieter under CPU load, and 2dB quieter under GPU load. The scores in my testing are also about 200 points higher across the board (CPU/GPU/Composite scores).

Unlike the be quiet! Pure Loop 2 FX 360mm, which is loaded up with ARGB and other glowy goodness, this be quiet! Silent Loop 3 420mm is silent both in operation and in colors. It does offer a bit of optional ARGB on the CPU plate itself, but the fans are pure black only. (There doesn't appear to be a white version available at this time.) That seems to be largely true for much of their product line; some are designed for a more stately look, while others go for RGB goodness. This product is more for those who prefer a more understated look.

It's also worth noting that these included fans are the Silent Wings 4, which is their flagship line of fans. They use a fluid-dynamic bearing that is rated for an insane 300,000 operating hours. That is approximately 34 years of continuous use. Most of their other fans are rated at a mere 60,000-80,000 hours - at least 9 years continuous. You can't say that this cooler comes with anything but the best.

After finishing the testing of the Silent Loop 3, I wanted to use some of the extra be quiet! fans that we were sent along with the review products (case, cooler). So, to get some of that ARGB bling back, and to improve performance just a bit more, I installed the fans in a push-pull configuration. What this means is that the include Silent fans are pointed up and mounted on top of the radiator, and the ARGB fans are also pointed up, and mounted under the radiator. With this configuration, there is twice as much airflow at the same fan speed, which cools down the radiator even faster than it would be normally. And, it looks cool. If you are disappointed that be quiet! doesn't offer an ARGB model of a 420mm at this time, then I recommend you try this, too. This is what it looks like:

The be quiet! Silent Loop 3 420mm all-in-one CPU water cooler is nothing short of an incredible product. It's bar none the best CPU cooler I've ever used, and both the high performance and low noise level is unrivaled in my experience. Unless I get into a minimalist kick that makes me want to rebuild my PC into a smaller form factor, I'm keeping this cooler on my CPU as long as I possibly can. The super low temperatures and near-silent operation makes this one of my favorite PC parts in quite some time. In combination with the 900 FX case, my computer can't get much quieter. After installing more fans into my case to operate the radiator in a push-pull fashion, I not only got more ARGB bling, but better cooling performance as well. This be quiet! Silent Loop 3 420mm gets my highest recommendation!