Be quiet! Silent Loop 3 420 review: Performance cooling with minimal noise

German company be quiet! (Henceforth referred to as Be Quiet) is well known in PC builder circles for its coolers and cases, which (as the company’s name implies) focus on low noise levels. The Dark Rock Pro and Elite air coolers performed excellently in our testing, and the Dark Base Pro 901 is personally my favorite PC case.

The Silent Loop 3 420 is the company’s largest AIO, and the latest to land on our test bench. Will it make our list of the best CPU coolers? Let's take a look at the specifications and features of the cooler, and then we’ll go over thermal and noise benchmarks so you can decide if this is the right large AIO for your next build.

Cooler specifications

Packing and included contents

The Silent Loop 3 arrives in a black box, showcasing the product on the front.

Included with the product are the following:

● 420mm radiator

● Three 140mm fans

● Mounting for AMD and Intel platforms

● Thermal Paste

● Extra coolant

● Cable management ties

Features of the Silent Loop 3 420 AIO liquid cooler

▶️ 140mm Silent Wings 4 fans

Three black Silent Wings 4 140mm PWM fans cool the radiator, featuring rated speeds of up to 1900 RPM, 78.4 CFM, and up to 2.36 mm H20 air pressure. As we’ll see in our testing, they deliver solid performance while running at lower noise levels than most competitors on the market.

▶️ Large CPU block suitable for Threadripper

The CPU block included with this AIO is large, and it supports AMD’s TR4 and TR5 Threadripper platforms. The tubes are fully rotatable, as is common with most AIOs.

▶️ Extra coolant

The cooler is DIY and user-repair friendly, with extra coolant and an accessible refill port in case you want to service the AIO after years of use.

▶️ (Optional) ARGB lighting on the CPU block

For those who prefer illumination, ARGB lighting is supported on the CPU block. Of course, if that’s not your thing, you don’t have to plug in the ARGB header. It has a sleek grey and black aesthetic without the lighting enabled.

AMD AM5 installation

1. First, you’ll need to connect the fans to the radiator, then secure the radiator to your PC’s case.

2. Next, remove the default AM5 brackets and place the included rubber standoffs.

3. Take the included mounting bars and place them on top of the standoffs, and then secure them with a screwdriver and the included screws.

4. Apply the included thermal paste to your CPU. If you aren’t sure how to do this properly, please refer to our handy guide on how to apply thermal paste.

5. Press the pump block on top of the CPU, and secure the built-in screws using a screwdriver.

6. Once complete, connect the PWM and ARGB headers to your motherboard, then installation is complete.

Real-world testing configuration – AMD AM5 platform

The 9950X3D setup that we started testing coolers with last year has suffered an unfortunate death. So we’ve begun to test coolers on a system with AMD’s 9950X.

There are some differences in how the 9950X and 9950X3D CPUs are impacted by thermal events – while the heat output of the CCDs of AMD’s 9950X3D are relatively balanced, the 9950X I’m using has one CCD that runs much hotter than the other, with a difference of over 10 degrees Celsius in some scenarios, shown below.

The benchmark results shared in these reviews may differ from others because I place an emphasis on having results that are comparable to real-world use.

This means that I generally test CPU coolers inside of a closed desktop case, which increases cooling difficulty compared to other testing methods - many will test CPU coolers outside of a case, on an open test bench. Open benches have lowered ambient temperatures, which in turn makes weak coolers appear stronger than they really are. Some publications have used generic thermal plates to test cooling solutions. I reject both of these methods because they don’t accurately reflect the real-world PC cooler conditions.

That said, this review bends this rule a little: The MSI Pano 100R PZ case that we use for cooler testing doesn’t technically support 420mm radiators. So I had to place it on top of the case to make it fit. This likely affects thermals and acoustics at least somewhat, but short of re-testing all our coolers in a different case, we didn’t have a better option.

We tested Arctic’s competing Liquid Freezer III Pro 420 in this same way for comparison, while the smaller 360mm coolers were tested in a typical fashion, with the radiator and fans inside the case. If there is heavy interest in large 420mm cooler testing, we will revisit these results in a larger case later this year.