How accurate are fans specs?

nails666 · 25 Sep 2014 at 20:31

Hi, I'm looking at getting some 140mm case fans and on here most of them show 3 main stats. They seem to be flow rate, noise and static pressure. Now comparing on them alone it seems some are clearly better than other, some examples below: -

Corsair AF140mm Quiet Edition - 66.4 (CFM) : 25.5 (dBA) : 0.8 (mm/H2O)
Corsair SP140mm - 49.49 : 29.3 : 1.17
BitFenix Spectre PRO 140mm - 86.73 : 22.8 : 1.38
Prolimatech Blue Vortex 140 - 87 : 18.1 : ???
Akasa Viper - 110.6 : 26.01 : 3.12
NZXT FZ-140 - 83.6 : 24.54 : ???

I've had various recommendations so far but when trying to compare fans based on the stats given they don't seem to relate very closely to what people say. For example the Corsair fans both SP and AF always get recommended (for radiators and cases respectively) but the stats seem to show that they are both worse than the others in all areas? For pure performance the Vipers look to be the best it's just a shame they only come is such a horrible colour and no LED version (vain I know but I want them to match my other components) so for me the BitFenix or Prolimatechs look best.
So is there some other aspect to fans that I'm missing that the Corsairs do well at?

I'm going to be running them from this Akasa fan controller if that makes a difference.

Any thoughts most appreciated,

Ross

pastymuncher · 25 Sep 2014 at 21:08

Manufacturers stats are rarely accurate compared to how a fan actually performs. Most are hopelessly over stated.

nails666 · 25 Sep 2014 at 22:17

Yeah that's kind of what I thought, makes choosing rather difficult.

CinderzFTW · 2 Oct 2014 at 13:51

fans are tested but each fan like a cpu is differnt even if made exactly the same, on the same line and in the same batch.

ttaskmaster · 2 Oct 2014 at 15:11

Important to know that high CFM means the fan generates good airflow, ie as a case fan, whereas high mm/H20 generates good static pressure and is better used in places where airflow is restricted such as radiators.
This is why the Corsair SP (Static Pressure) and AF (Air Flow) fans seem so vastly different.
Some manufacturers also do all-rounders, like Noctua.

Start by splitting the fans these fans into the above groupings and then comparing them like for like.

Consider noise levels, but be aware that even the quietest fans can get noisy (generally above 1000rpm) and that noise is often the airflow itself moving through grilles, meshes, radiators or just the fan holes themselves.

User opinions may help, but you'd need to look at many and average them out.

Lastly, it all depends on your own particular setup anyway. You may need a bit of trial and error to get things working along the lines of what you're looking for.
A lot of fans at low rpm often gives better cooling than a few high-powered ones blasting away, for example.

For the record, I like Corsair fans, but found them a bit noisy. Silverstone do some nice low-cost fans.
I am currently using mainly Noctua fans, with a couple of Enermax ones.

doyll · 2 Oct 2014 at 19:00

Fans of the same model test almost identical and not at all like overclocking CPUs.

But the specs given for most fans are not accurate.

The other problem is the specs, even if accurate are not spec of how we use fans.

The airflow reading (CFM) is fan blowing full speed with no resistance .. usually hanging in an open chamber.
The Static pressure reading (mm H2O) is how high water is in tube when the fans stops moving air.

Neither of these is the way we use fans. We have at least a grill restricting the airflow and often a filter as well .. even a decorative grill filter 2nd grill and finally inside of case a HDD cage and / or cables. All of which cause restriction to the airflow.

This means we need a P/Q curve of fans performance, and very few companies give us this.

As a result the best way to evaluate fans is find a reviewer who tests them on a radiator and give their airflow and noise specs or temperature and noise specs. With this information we can see how well the fan overcomes resistance and flows air to keep things cool. Martin's Liquid Lab has good data.
http://martinsliquidlab.org/category/fans/

I sometimes use Hardware.FR If you use them make sure you are using the results on radiator, not open air.
http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html

nails666 · 3 Oct 2014 at 21:06

Thanks for that all, some useful info there.

Damo667 · 4 Oct 2014 at 01:27

i have corsair sp120 performance in one pc with an sp120 quiet in it too and my 2nd pc is all akasa viper 120 and 140.

im also using the phobya equivalent of your fan controller as the akasa one was out of stock at the time.

performance wise sp120 are excellent i have 4 on 2 x 240mm radiators. the quiet doesnt perform as well due to it being a slower speed which is where your decision is. if you want quiet fans id use the quiet edition and run them flat out with or without the controller. the performance version are like a jet engine at takeoff so id definitely use a fan controller.

akasa vipers i actually like the colour and its not a windowed case or anything so not fussed. they are about the same as a hdd imo at full speed. performance wise i havnt done an apples to apples comparison but my fx4350 at 5ghz only running a corsair h60 is pretty happy temp wise.

cant fault either fans just downside to sp120 performance being really loud. with sp120 you can also remove the coloured rings and paint them whatever colour you want and not risk damaging the fan itself.