About fans, rpm, silence, etc...

[b4u]

Hi,

This is a series of quick questions regarding how the fans are connected, operate, etc... I'm gathering some knowledge to make a case purchase and eventually some extra fan(s).

1# Are 140mm fans expected to be substantially better than 120mm ones? I'm talking about similar fans, with same technological characteristics, so they can be compared. Is a 140mm supposed to bring substantially more air?

2# Would it be better 1x 140mm front intake, or 2x 120mm front intake? Would I be better with the latter? (noise would be higher, and power consumption, I know)

3# I read about 2-pin and 3-pin fan connectors. Does the 3rd pin bring the rpm signal? If I connect such a fan, would I be able to theoretically control the rpm fan speed on mobo software? And would it really be worth it?

I'm looking into http://www.nzxt.com/new/products/classic_series/h2 which looks to have 2x 120mm front intake, that connect with 2-pin contacts for easy removal without cables getting in the way. So it is supposed to be connected to the fan speed controller on the case, so no connection to the mobo, makes sense? Then the rear and top exaust fans would be connected to the mobo, and able to be rpm-controlled, am I thinking right?

I don't have many experience with fans, fan controllers, nor the 2-pin, 3-pin, n-pin connection types, so your opinions on the terrain will certainly be welcomed.


Thanks

 

[joetekubi]

In general, for low noise, you want to run large fans at low rpm. I'd suggest that 2 X 120 fans would push a lot more air than 1x 140 fan. I really like my Scythe SlipStream fans, but I hear NoiseBlocker is good also.

I've got a Zalman CPU cooler with an external manual rpm adjust. Love it. All noise vanished when I lowered the rpms to about 900.

 

[Zap]

1) If spinning the same RPM, longer fan blades move more air.

2) 2x120mm will still have more surface area than 1x140mm for moving air. Not that this is accurate (too many variables such as fan hub size, gap between blades & cage, etc.) but 2x120mm is 28800mm² while 1x140mm is 19600mm².

3) Yes, generally speaking 3rd wire (usually yellow color) gives RPM. Fan speed control (except for 4-pin PWM) is done through modifying voltage. Some headers on some motherboards will allow adjustments to be made, either through the motherboard BIOS, through software bundled with the motherboard or through third party software like Speedfan. Note that not all fan headers on all motherboards can be controlled in this fashion. Usually (but not always) the 3-pin ones can, but the 4-pin PWM headers often can only control a PWM fan.

 

[darkware]

It's worth pointing out that there are many more choices of 120mm fans than there are 140mm fans and manufacturers are still working to optimize mechanics and designs for 140mm. At the moment, there are only a handful of 140mm fans which can match the upper levels of the 120mm fan market.

Thus, generally, you should expect a 140mm fan to be louder than a 120mm fan, even when pushing a similar volume of air. This becomes even easier to say when talking about 200mm fans.

Notable exceptions here would be the 140mm Slipstreams and the Thermalright TY-140, both of which seem to be amazing fans. However: they use 120mm mounting holes. Honorable mention for the Prolimatech Red Vortex, which has 140mm mounting holes.

Even then, if silence is a priority, you'll get more air movement and less noise off a (good) pair of 120mm's than a single 140mm.

 

[stahlhart]

I was surprised at how quiet these turned out to be, for being relatively inexpensive "stock" 140mm fans:

http://www.performance-pcs.com/catal...ducts_id=26958

 

[b4u]

Does anyone know if an Asus P8P67 EVO 4-pin PWM CPU fan header allows the RPM control of a 3-pin fan?

Because I'm connecting a Corsair A50 CPU cooler that has 3-pin ... latter on, I could replace the fan for a PWM one, but for a start, I have the new one that comes with the cooler, so I'm not interested in changing it.

Also, the PWM is controled by the mobo? I read somewhere that the temperature readings of the mobo aren't the most accurate, so if this is true, it would erratically manage the PWM fan speed ... correct?

So would I be better to put a 3-pin fan over a 4-pin PWM one?

Thanks

 

[piasabird]

I like to think of a computer case like a Guitar. Some cases tend to be designed more like an echo chamber than a wind tunnel. It is true that the video card, the RAM, and the Processor all generate a lot of heat, however, often cases put the drives in the top of the case, so if you do not get rid of that heat, then it can ware out your optical and hard drives. That is just something to think about.

 

[Termie]

Does anyone know if an Asus P8P67 EVO 4-pin PWM CPU fan header allows the RPM control of a 3-pin fan?

Because I'm connecting a Corsair A50 CPU cooler that has 3-pin ... latter on, I could replace the fan for a PWM one, but for a start, I have the new one that comes with the cooler, so I'm not interested in changing it.

Also, the PWM is controled by the mobo? I read somewhere that the temperature readings of the mobo aren't the most accurate, so if this is true, it would erratically manage the PWM fan speed ... correct?

So would I be better to put a 3-pin fan over a 4-pin PWM one?

Thanks

In my experience, the 4-pin CPU fan header will not control a 3-pin fan. I have that issue with my p7p55d evo motherboard, and thus I have a manual fan controller attached to my 3-pin fan and then to the 4-pin header.

 

[ElFenix]

the 4th pin is a control signal for the fan. without it, the fan won't use actual pwm control.

there are 3 pins headers that can control, but those work by supplying lower voltage to control rpm. true pwm allows for full voltage to be applied at all times which helps with startup (more force/voltage is required to start a fan than to keep it running once it's moving).

 

[zagood]

ElFenix alluded to voltage fan control. You should be able to change fan control method in the motherboard BIOS from PWM to Voltage control for 3-pin fans. Just make sure you don't set your minimum fan speed under 50%. Check your user manual, not all motherboard fan headers offer this.