PWMs v DC fans ?

EsaT said:
Actually definitions of those marketed numbers are strict and don't allow any variability:
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Exactly. The measurements are constants, but will be affected by the variables of a particular build, which is why a fan could be great in my rig but perform worse in yours.
Same for the P-Q curve, which is why that too is not by itself any kind of definitive indicator, as Martin's Liquid Lab quite clearly points out.
 
ttaskmaster said:
Exactly. The measurements are constants, but will be affected by the variables of a particular build, which is why a fan could be great in my rig but perform worse in yours.
Same for the P-Q curve, which is why that too is not by itself any kind of definitive indicator, as Martin's Liquid Lab quite clearly points out.
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Max airflow and static pressure of the fan won't ever change.
(except when changing RPM)
What changes is the point where fan operates somewhere in that mid section of P-Q curve.

Even minimal impedance finger guard made from round wire drops speed of airflow 16%:
https://www.silverstonetek.com/techtalk_cont.php?tid=wh_chessis&area=usa
And very few cases use such meaning usual impedance is higher with fan moving still farther from max airflow.
 
EsaT said:
Max airflow and static pressure of the fan won't ever change.
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Which is what I said...

EsaT said:
What changes is the point where fan operates somewhere in that mid section of P-Q curve.
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No more than at any other point, otherwise if it did change there would be no point plotting such a curve in the first place.

EsaT said:
Even minimal impedance finger guard made from round wire drops speed of airflow 16%:
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Assuming every single fan is absolutely identical to every other... which I'm sure you understand is not the case.
Different fans, different airflow spread, different interactions with restrictions.

Do you have a point with all this, or are you just going to keep posting half-read, misunderstood links that do nothing to support your position of misinformation?
 
ttaskmaster said:
Which is what I said...

Do you have a point with all this, or are you just going to keep posting half-read, misunderstood links that do nothing to support your position of misinformation?
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Ehem...


ttaskmaster said:
Same for the P-Q curve, which is why that too is not by itself any kind of definitive indicator, as Martin's Liquid Lab quite clearly points out.
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Whole point of that article is that max airflow and static pressure are anything but good indicators of true performance, while P-Q curve is the best indicator of what kind performance is in real world.

Since most fans out there don’t bother publishing P-Q curves, you essentially don’t know what there real world performance will be...

Just like pumps, it’s the pressure somewhere between these two points that matters in the real world and that isn’t static pressure and it isn’t max air flow, it can only be represented by a full P-Q curve.
https://martinsliquidlab.wordpress....w-specs-are-poor-measures-of-fan-performance/​

And that's supported by fan comparisons, in which marketing numbers of the fans usually don't show much any correlation to results.
 
As I have already explained to you in previous threads where you've spewed out your ill-conceived ********...

EsaT said:
Whole point of that article is that max airflow and static pressure are anything but good indicators of true performance, while P-Q curve is the best indicator of what kind performance is in real world.
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"All this post talks about is trying to convey what static pressure and max air flow are"
Martin of the Liquid Lab, in the very same article you quoted.

"This just means the two spec we often use for comparison are an incomplete picture and should be relied upon 100%. The only way to truely compare actual performance would be to compare the entire curve"
Again, from your god Martin himself.

But again, all of this goes right out of the window when it comes to installing any given fan, because your oft-bleated P-Q Curve does NOT account for actual real world variables such as the physical characteristics of whichever restrictions you're installing it against, or the airflow spread that will create compression and stalls. It is just one (but not the only, and certainly not a complete) method for comparing one uninstalled fan against another uninstalled fan. It has no practical meaning and gives no better indication of cooling performance than static pressure and max airflow.

So unless you test every different fan actually in-situ, whereupon you will find your results strangely do not concur with your P-Q Curve predictions due to those variables I mentioned which you so readily ignore, your curves and stats are nothing more than a starting point and guesswork.
 
I’ll likely be going against the grain here but DC has its advantages or at least what I perceive as advantages over PWM fans and pumps.

Who cares about running fans at low RPMs if you’re at the point of passively cooling everything - you’d be just as well to switch the fans off.

Good fans are silent even at high RPMs so I don’t see the attraction of adding variable acoustics to your setup if the point of diminishing returns is already inaudible.
 
Bluntwrapped said:
Good fans are silent even at high RPMs so I don’t see the attraction of adding variable acoustics to your setup if the point of diminishing returns is already inaudible.
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Good fans are silent, yes... but their airflow over the heatsinks still makes noise.
Running PWM allows lower fan speeds and lower noise while maintaining cooling - In my case, with Push-Pull fans at 1100rpm, I get the same cooling as Push only at 1800rpm. I'm still playing with stuff, but I know I could get the fans to dead silent around 4-600rpm and still cool as well as if I had a single bank at 1300. It's far from passive, but it performs as well.
 
ttaskmaster said:
But again, all of this goes right out of the window when it comes to installing any given fan, because your oft-bleated P-Q Curve does NOT account for actual real world variables such as the physical characteristics of whichever restrictions you're installing it against, or the airflow spread that will create compression and stalls. It is just one (but not the only, and certainly not a complete) method for comparing one uninstalled fan against another uninstalled fan. It has no practical meaning and gives no better indication of cooling performance than static pressure and max airflow.
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So all actual fan manufacturers (and industry using fans) calling P-Q curve even as performance curve are liers?

P-Q curve is precisely what tells how fan behaves when facing different amounts of back pressure.
And fan with bulging curve does better in real world than max airflow and static pressure numbers imply, while fan with curve bent toward lower left does worser.
Just like how NF-A12 does so well in every fan comparison/review, despite of having only mid level airflow and static pressure numbers.
Basing on those two paper stats NF-A12 would be Noctua's worst fan...

https://ebmpapst.com.au/media/conte...TTM-02_Determination_of_duty_point_of_fan.pdf
 
Bluntwrapped said:
I’ll likely be going against the grain here but DC has its advantages or at least what I perceive as advantages over PWM fans and pumps.

Who cares about running fans at low RPMs if you’re at the point of passively cooling everything - you’d be just as well to switch the fans off.
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DC control's slow speed advantage depends on particular fan.
Some fans can start at really low voltage and can be adjusted through wide speed range.
While others need notably higher starting voltage compared to voltage at which already turning fan can maintain operation.
In those fans setting voltage low is risk of fan not starting, unless used control system supports start up boost.
(/boosting when it detects fan having stopped)

PWM fans again manage speed using their internal control circuitry...
Which as rule force minimum speed protecting motor from any states of not turning properly, but at the expense of not allowing fan to be stopped by PWM control.
Though some fans like Arctics again have zero RPM mode for when PWM duty cycle goes below 5%.
 
EsaT said:
So all actual fan manufacturers (and industry using fans) calling P-Q curve even as performance curve are liers?
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No, your understanding of what has been presented (by myself and others) is inaccurate.

EsaT said:
P-Q curve is precisely what tells how fan behaves when facing different amounts of back pressure.
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Yeah?
Then tell me exactly where on your all-telling P-Q Curve you will find the airflow spread?
Two fans with the exact same P-Q Curve will perform very differently if one has a wider spread, and that makes far more difference than open air stats at any point along a graph.

To use your car analogy - Your car might do 0-60 in 3 seconds on a test track and have the best mid-range revving engine on the planet... but it certainly won't be performing like that on wet grass, where conditions aren't test track perfect.
All you're doing here is swapping max stats for medium stats, but they remain the same paper stats. If it were otherwise, every manufacturer would be throwing around P-Q Curves and we'd all be using the same 'best' fan model, as the choice would be so simple and obvious.
 
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