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Thread: undervolting vs pwm help me out!

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    undervolting vs pwm help me out!

    For a little project I need some super low speed SLIM 120mm 500rpm fans. So i had undervolting the 120mmx120mmx20mm 1350rpm yate loons in mind but they only undervolt to 6v (consistently apparently) which based on a quick bit of reseach means they will spin at around 800rpm ... I want quieter!

    So I was wondering if I bought a BigNG which allows you to pwm fans do you reckon I could get them close to 500rpm without any horrible ticking noises?

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    Re: undervolting vs pwm help me out!

    ?? just get a quiet fan to start with.

    Akasa apache 120mm http://www.scan.co.uk/products/120mm...r-pins-1500rpm

    25mm thick 16dbA

    Why do you need slim fans? Can you really not handle another 5mm?

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    Re: undervolting vs pwm help me out!

    Personally I wouldn't worry so much, the big issue you get under 1000rpm is motor and/or bareing noise.
    Below 1000rpm the blades move so slowly through the air that they generate almost no noise.

    If you want totally silent fans then be prepared to spend on more expensive fans with higher quality bareing and motor.

    Have a look at the 800rpm scythe slip stream SLIM SY1212SL12SL
    I cannot find that off hand 1200rpm version here http://www.specialtech.co.uk/spshop/...pid-10543.html

    Most fans will run on 5v but the issue is starting, many fans need between 6-6.5v to actually start.
    Other issue is that as you undervolt some fans will develop motor buzz.

    With the requirement of 20mm thick or less, you're very limited in fan choice, you may well have to try a couple of different options to find out what's best.

    One other thing to remember is that at very low speeds air being pushed through punched metal grills often generates more noise than the fan on it's own, cutting out metal grills can often reduce the noise of a very quiet fan.

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    Re: undervolting vs pwm help me out!

    Yeah it is tough call. I had looked at those scythe ones, my only concern is that the environment is going to be fairly restrictive and I am not sure whether they will have the static pressure to cope. The 20mm yate loons I have heard don't perform that much worse than the 25mm variants.

    I suppose I can either go a different way which doesn't require the 20mm fans or alternatively just get the 20mm yates as slow as I can without buzzing or ticking and just accept it.


    hmmmm thanks for all your help anyway guys .

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    Re: undervolting vs pwm help me out!

    I'm still curious why you feel constrained to 20mm fans - your case is large enough for bigger ones, or is this for another machine?

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    Re: undervolting vs pwm help me out!

    oh it is for another case and my sig is very out of date lol. I wanted to do a mod to squeeze a quad radiator in the roof without interfering with mobo, but no one makes a super slim quad ... only super slim triples. So I might just do a slim triple and use normal fans ... shame really because I would probably just have enough room for a quad ... but oh well

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