ARCTIC S4028-6K - 40x40x28 mm Server Fan, 250–6000 RPM, PWM Regulated, 4-pin Connector, 12 V DC, Rack Cooling Fan - Black

I picked up one of the 6,000rpm variants of these fans to aim at the 12VHPWR connector on my RTX 5090—you know, just to be safe. I even 3D printed a little right-angle duct adapter to funnel air down over the connector itself. Ultimately, I ended up removing it from the system because I found the noise output unacceptable, even at very low operating speeds. ➤ The Challenge with 40mm Fans 40mm fans can be tricky with noise. Twenty to thirty years ago, 40x10mm was a common size on chipsets and video cards, and I've had quite a few fans in that form factor that were essentially inaudible when installed in a case. I've also had other 40mm fans—like these Arctics—that produce specific tones that pierce through just about anything you mount them to or in. In terms of quantitative noise levels, these are very quiet fans for what they are. I have some 40mm Sanyo Denkis on a 2.5" drive cage that max out at about 13,000rpm and are audible across the house at 8,000rpm; these Arctics are nothing like that. Qualitatively though, the noise these produce is specifically irritating to me. I can sit next to the server with those Sanyo Denkis screaming away and after a few minutes stop noticing them. A cynic might point out that this is because after a few minutes next to that server, I've gone deaf, but this is neither here nor there. By contrast, the single Arctic I had on the 5090, running at ~2,000rpm, was far more irritating in spite of being far quieter. It was *just* audible as a faint ticking buzz over the rest of the system. And unfortunately, at ~2,000rpm, it didn't move enough air to make a difference in my use case, so it was just added irritation with no benefit. It's not that they're loud—it's that the specific tone they make, even in the context of what they are, is particularly grating to me. But this is intrinsically subjective, so your experience may differ. ➤ Use Case Matters For their intended use case (in a 1U server), these are extremely quiet and highly power efficient. For use in a desktop, they become meaningfully audible far before they move a meaningful amount of air. As far as 40mm fans go, these are outstanding. But unless you have a specific need for a 40mm fan, you would generally be better served finding an alternative way to accomplish whatever task you're considering these for. ➤ Bottom Line I can't and won't knock any stars off the fan itself—these earn the full five stars easily. They're power-efficient, quiet for what they are, dual ball bearing, exceptionally well-built, and Arctic provides actual performance data including P/Q curves and PWM curves. Both are generally absent with consumer-grade fans and are hugely useful if you know how to read them, signaling that Arctic is serious about selling these for actual industrial/server use. For the home/enthusiast/desktop user, these are clearly audible below 2,000rpm, and probably outright unacceptable over 3,000rpm. If you have a specific need for them, I'd recommend them very highly. On balance these are likely the best 40mm fans on the market. At the same time, if you can accomplish your goal with a larger fan, you'd probably be happier going that route.

I have bought multiple packs of the 6K and used them all over. Imo I would say the difference in noise between these and a Noctua is fairly neglible so don't believe those that say these are insanely loud. I may be biased because I am replacing MUCH louder fans in old server equipment so anything quieter is a blessing, however I have tested the Noctua and the 6K version side by side in a quiet computer room of mine and even being next to them on full blast these were barely audible. I hooked them up to a bench top power supply giving 12V DC so there was no confusion of if they were each on full blast or if the noise was being muddied by other fans. I think the Noctua is a better pick if you absolutely value complete silence above all and you intend to use these in a computer that you have tuned to full blast. Otherwise with PWM I would pick these 100% of the time - they're much cheaper AND they move MUCH more air than the Noctuas, which is another great benefit in old server components -- I need the airflow. Ultimately these are a great buy and I would definitely recommend them!

Works great, not too loud

Hooked from a 12V 1A power supply w/ barrel connector to terminal connector to the fan, following the diagram shown in the picture. The diagram is backwards. Reversed to other side of pins, ground on outside, positive on inside, and it worked. Ran through a PWM controller then to fan connector, and spins right up. It'll move quite a bit of air for it's tiny little size. Put this on top of a SBC in an aluminum case, on slowest the PWM controller will let it, and it's *fairly* quiet. Turn this little thing to max, and it gets fairly loud. Moves quite a bit more air than a 120mm high flow case fan. -1 star for the incorrect pinout, picture is accurate. No mounting hardware, will have to purchase/reuse depending on application. Unsure quality, that'll be a longevity thing. As far as value - I bought it because it was cheap, I knew it didn't have hardware, but for my application, needed some modifications anyway, so no big deal for me, YMMV.

These fans are a bit louder than I would have hoped for, but they're still quieter than what they replaced. I did some math before buying and determined that the 6K variant would not be enough for my use case on a Tesla P40. That was correct, as these fans have to be at 11-12K RPM to keep temperatures under control. Under a more moderate load, they can run at 9K or less to keep it cool. Overall, if you're trying to cool a 250W TDP or so GPU like a Tesla P40, these work fairly well for the price.

Man can these things move air. Just be warned, these are not a fan you would put in a switch located in a bedroom or a noise sensitive area.

Original fans on the Ubiquiti US-48-500W had a lot of coil whine. Switched them out for these. Coil whine gone and probably cooler with the top on whenever I cut some of the back out to fit the aftermarket PSUs since the original PSU was dead when I got it. Took all of 5 minutes to switch it out.

No frills, no marketing bs, just pure performance. I needed good 40mm PWMs to cool my optane rams and these were perfect. I would have gotten the normal AVC used in servers but they're too loud. The 11k RPM version of this would work just as well and is also quiet compared to the AVC but it was not needed for this use case. The rams were hitting 70c prior without proper airflow. They peak at 43c with these fans mounted on top.

El performance de los ventiladores es muy bueno definitivamente cumplen con su función, tanto para servidores, NAS o para agregar un extra de ventilación a los headsync de la tarjeta madre funcionan a la perfección, el flujo de aire es bastante bueno y con bajo nivel de ruido. en comparación con la competencia NcTua, creo que valen cada peso de lo que cuesta el paquete de 5 es excelente y son PWM

I bought 2 of these fans to use in my remote control vehicles. I had to convert it to a 3 wire plug, (YouTube has a video using these fans) but they really pump the air and keeps my motors a lot cooler when bashing on my trucks.