Fan Picking help.

[Ghost]

My first question is how does PWM help? I know what it does. But how does it help? I am looking at some Noctua 140mm fans and am slightly off put by the fact they don't have PWM. Is this something to be worried by?

Secondly what would you recommend for a 140mm radiator fan if price wasn't important.

Last of all how much space between fans do you need for the noctua a15s to work? I am slightly confused. Will they fit side by side in a standard fan spacing of 15/20mm (for 140mm fans).

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TLDR; I need to buy 2*120mm rad fans, 1*140 fan (absolutely no obstructions), 1*140 fan (pushing at the HDD cage), 3*140 fans for a rad on top, 1*140 fan for a rad at the back. I want to be able to set up fan curves for them with Fan Xpert2 on an Maximus V.

What should I pick?

[xeks]

Read somewhere on the interwebs:

PWM for motor speed control works in a very similar way. Instead of supplying a varying voltage to a motor' date=' it is supplied with a fixed voltage value (such as 12V) which starts it spinning immediately. The voltage is then removed and the motor 'coasts'. By continuing this voltage on/off cycle with a varying duty cycle, the motor speed can be controlled.[/quote']

The A15 PWM has a 140x150x25 dimension so I'm not sure if that will fit your rad if your rad is designed to fix 3x140 perfectly. What three rads are you using so we know their spacings?

[Ghost]

Read somewhere on the interwebs:

PWM for motor speed control works in a very similar way. Instead of supplying a varying voltage to a motor' date=' it is supplied with a fixed voltage value (such as 12V) which starts it spinning immediately. The voltage is then removed and the motor 'coasts'. By continuing this voltage on/off cycle with a varying duty cycle, the motor speed can be controlled.[/quote'] The A15 PWM has a 140x150x25 dimension so I'm not sure if that will fit your rad if your rad is designed to fix 3x140 perfectly. What three rads are you using so we know their spacings?

The A15 isn't for the rad its for the front panel.

I was going to use some other 3pin Noctua or find a 140PWM fan for the rads.

Let me grab my useful diagram of my case.

1/2/3 will all be connected to a 420 mm rad.

[xeks]

What rads do you have?

[Ghost]

What rads do you have?

I cant really tell you off the top of my head. They are quite low FPI ~10 but they are about 5-6cm thick.

[MG2R]

I think the main reason PWM is introduced is to make motherboards/fan controllers easier to design/manufacter. A voltage controlled (3-pin) fan gets driven on a motherboard by PWM coupled to a low pass filter (resistr-capacitor pair). That's the way the motherboard makes a varying voltage. So if your fan speed can be controlled directly through PWM, there is no need to add the extra low pass filter.

The question 'which is better, PWM or voltage controlled?' can be answered with PWM, I think. I don't know this for sure, but my guess is PWM fans have the potential of spinning at a (marginally) lower speed. I think this because a fan (and any electric motor for that matter) needs a certain starting voltage, after the motor is spinning, you can go below that starting voltage without stopping the fan from spining (this has to do with static and dynamic friction, for those of you that know a thing or two about physics). With PWM control, you always have 12 volts delivered to the fan no matter what, so even though the burst are short, they are still powerfull enough to get the motor *moving* and once its moving you have dynamic friction instead of static friction, so you win. But as I said: I'm not sure about this :p

Basically, it boils down to this: does your motherboard/fan controller support both voltage based and PWM based control? Go with either of the two and be happy. Does it only support one of the two? Go with what it supports and don't worry about which is better, they both work.

[Helltech]

Noiseblocker PK3