Ty :)

So the fan decides the max RPM possible and the fan controller (probably the Motherboard) decides the percentage of the available RPM with the duty cycle?

The username was a bit of a giveaway.

Their claim about Noctua is also not correct, or at least not generalisable to all coolers. I upgraded my CPU recently to a Ryzen 9 5950X, so needed to upgrade my cooler. The NH-D15 came out as one of the best options (that were also available second hand) when looking at cooling performance per dB. That ratio is what matters.

I ended up spending about $45. It ended up not having all fan clips with it, but Noctua sent those to me for free.

I wasn't being a dick for no reason - I was being a dick because I thought THEY were being a passive aggressive dick, much like how you assumed I was "gatekeeping knowledge to feel superior". Bad assumptions all around here.

I assumed they were suggesting PWM will cause an inherently slower spinning fan to spin at any RPM regardless of model, which is actually a response some Noctua diehards have used in the past when I point out what Noctua is omitting when they advertise their fans as being so much quieter.

Regardless, I apologized for my bad assumption and subsequent response. It was out of line, especially given the actual meaning and intent of the comment.

You were downvoted because you're wrong, or at best technically accurate but inaccurate about the results.

Your fan speed is set by your fan controller.

And while it's true that different fans can be set up to spin at different speeds with the same input voltage or PWM signal, if the fan is less effective at cooling at that rate, the controller will end up higher on the fan curve and speed it up to compensate.

The only things that determine your fan's ultimate speed are a) how high the controller allows it to go, b) how much heat the hardware is generating, and c) how efficiently the combination of coolers and fans dissipate that heat into the air (which also depends on the room's conditions).

Now we're just talking about fans, so we can ignore item b entirely as well as the cooler and room conditions. And it then comes down to, can the fan keep up with the heat being generated at the current point in the fan's curve? If not, heat increases and the controller speeds up the fan. Then, when it hits whatever the cap is, if it still can't keep up, the hardware either overheats or throttles.

If it can keep up, then it stays where it is on the curve. If it can dissipate more heat than is being produced, it goes down on the curve and the fan slows down as the temperature lowers.

All this to say, if you have fan A that needs to be at 2000 rpm to keep up with the heat being generated by the hardware at say 65°C and someone says they have a better fan, B, that is just set to spin slower at the same signal from the controller, all that will happen is it will fail to keep up with the heat generated at 65, then the heat will rise until it's spinning at 2000 rpm anyways or the curve hits the cap and the system throttles to reduce the heat generated.

So we couldn't really eliminate that item b above and it could actually be relevant, though if that were the case, I'd assume people would just curse noctura because their fans suck and their systems run hotter or slower. But they have a good reputation where the main complaint I see is about their price, not their performance.

Personally, I use be quiet! fans rather than noctura, but it's a similar principle. They make quieter fans by tweaking or redesigning blades shape and angle, bearings, and the motor. Blades make them more effective at slower speeds, and all three can make them quieter at the same speeds.