• 2 Posts
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Joined 3 years ago
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Cake day: July 27th, 2023

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  • I disagree about why I got downvoted, but I don’t care enough to argue the point.

    You’re correct about the temperature/duty cycle curve, but not “the only things that determine maximum fan speed” and what that means in relation to that curve. I’m loath to toot my own horn, but the concepts you’re describing and are claiming I don’t understand are what I work in professionally. I mentioned earlier I’m an EE - an electrical engineer.

    Maximum fan speed is inherent to the fan itself and, put very simplistically, in a brushless DC motor is determined by the torque generated. As the motor spins faster, the total resistance (again simplistically, back EMF and net friction) increases, and once it equals the motor’s torque output, the motor has reached its maximum speed. Fans operating at a given voltage will have different maximum speeds based on blade size and geometry and motor design.

    PWM fan controllers simply correlate a temperature with a duty cycle percentage, but cannot cause a fan to spin faster than its maximum speed. If one fan is rated for 3500 RPM and another 6000 RPM, they will spin at their respective rating at 100% duty cycle. No more.

    Noctua’s fans in general tend to have engineering superior to many lower priced alternatives, somewhat reducing the sound generated at a given speed, but the low-noise line of fans for which they are often noted achieves that low noise primarily through reduced speed, and thus reduced output. Similarly, the low noise adapter included with some fans is simply an in-line resistor, also reducing speed for reduced sound.







  • 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.


  • So sorry! I mistakenly assumed you were amongst the “downvoting for sharing information they don’t like” crowd that hit my original comment, so I read your comment as being passive aggressive. My response wasn’t any better than what I assumed BUT mine was entirely intentionally, so I was absolutely the one in the wrong. I apologize.

    I assumed your response meant “PWM will spin up the fan to equal RPMs regardless of model”, which is actually pretty similar to what some Nortua diehards have claimed on Reddit when I’ve criticized Noctua fans in the past.

    The other commenter has the right of how PWM works. Since it only modulates the frequency and therefore duration of on/off cycles, if one fan spins at a max of 6000 RPM while a Noctua equivalent tops out at 4500, PWM will only be able to modulate to speeds below that maximum.