Very Odd? 3 pin fans much quieter on PWM Mobo Headers

daveyg

daveyg

daveyg

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Ok, here is a strange one for you all:

I have a Anidees AI-6 case (very nice) and had a pair of 140mm Corsair AF Quiet Edition fans (3 pin) installed in the front.

Using the cases's inbuilt fan header I had them running straight off my PSUs 4 pin molex (12v).

Even with the speed reducer installed they made an absolute racket and I was not at all impressed with them at all, they drove me mad.

I have now just upgraded to an Intel DZ77RE-75K mobo with all onboard PWM fans.

The strange thing is my hugely noisy fans are now almost completely silent (and yes they are turning) when I connect each up to a PWM (4 pin) header.

Does anyone know what is going on? I thought PWM was supposed to chuck out 12v so they would run at full chat.

Happy but confused, (so long as the temps are ok)

Cheers,
Dave.
 
The board you have is capable of voltage controlling 3 pin fans as well as PWM ocntrolling 4 pin PWM fans, a lot of good boards do this, my ASUS RIVG does. The irony being why the hell would anyone want PWM when they have voltage control lol.
 
In you opinion is it better to have voltage control of a 3 pin fan than PWM?

Is set and forget your thinking?

(I was about to buy some PWM fans)
 
PWM sometimes have some noise issues at lower RPM where the 'kick' of the 12v PWM can be heard. You shouldn't be able to hear it really as PWM operates at above 20kHz and should be silent to our ears.

You should be able to run a PWM fan slower than a voltage controlled fan, provided the fan isn't internally limited (sometimes they are).
 
I have that as well.
I scrapped my old Corsair case for fans and other parts when moving to other case and those AF 120s were very noisy when I used them with fan controller at first (they are 3 pin fans).
Then I connected them to motherboard 4 pin connection and they are happily cooling my h40, cant even hear them really.
 
Tealc said:
PWM sometimes have some noise issues at lower RPM where the 'kick' of the 12v PWM can be heard. You shouldn't be able to hear it really as PWM operates at above 20kHz and should be silent to our ears.
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I don't think I have super hearing so must just have bad luck with fans, then again my system is tuned for silence. I find that Noiseblocker/Akasa PWM fans tick at low speed and Corsair SP PWM tick at medium speed. It really annoys me to the point I replaced them all with GT's, job done :)
 
ubersonic said:
I don't think I have super hearing so must just have bad luck with fans, then again my system is tuned for silence. I find that Noiseblocker/Akasa PWM fans tick at low speed and Corsair SP PWM tick at medium speed. It really annoys me to the point I replaced them all with GT's, job done :)
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You're not alone on that, my Scthye Mugen CPU cooler fan is PWM (and scythe are a good brand when it comes to fans) ticked or sounded like it was brushing against the sides so much that I replaced it with a Nexus 12cm 3pin case fan. The only problem I have now is my mb doesn't support voltage speed regulation via the CPU fan headers so I'm now looking for a PWM to Voltage converter. Finding decent PWM fans is a challange, especially so when you're building a PC to be as quiet as possible.
 
Is the noise the only reason people dont like PWM fans? From an electronic design perspective, I'd far rather design for PWM fans, as PWM control logic is vastly cheaper to implement, especially as the fan power goes up.
 
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