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Discussion Starter · #1 ·
This is just a quick graphing demonstration of why fan box specs using static pressure and max air flow are generally poor tools in comparing fan performance. Very much like pumps, fans have a pressure vs flow rate relationship that is not at all linear. Some are flat some are curved, some have big bumps and dips and it's the area between these two points that ultimately matters, not what is at the ends.

For example, let's compare these two fans using box specs:

Cougar Vortex PWM
http://www.cougar-world.com/fileadmin/downloads/COUGAR%20VORTEX%20PWM.pdf

Max Airflow = 70.5CFM

Static Pressure = 2.2 mm H20

Gentle Typhoon AP-15
http://www.nidecamerica.com/fanpdfs/d1225c.pdf

Max Airflow = 58CFM

Static Pressure = .08inwg = 2.03mm H20

Using these specs alone you would assume the Cougar would produce more air flow on a radiator. Both max air flow and max pressure are greater, you can't go wrong with that can you?

Well, luckily both of these fans do provide P-Q curves(Most do NOT), so I spent some time cropping out their P-Q curves, converting units and overlaying them. First here are their native P-Q curves in different units of coarse making a comparison difficult.

cougarvsgt15part2.png?w=614&h=1500


So I brought both into Excel and plotted them out the best I could, here is how that looks:

cougarvsgt15part4.png?w=614


In addition noise box specs are "Open Air" with no restriction and no adverse "Real World" affects when mounted to a radiator. Since most fans out there don't bother publishing P-Q curves, you essentially don't know what there real world performance will be and the noise specs don't mean much on a radiator either.

And I'm not trying to pick on the Cougar fans either, I want to try some myself. That's still very impressive at only 1500RPM and I have to check them out. My point was to demonstrate how static pressure and air flow specs do a piss poor job at comparing fans.

Hope this muddy's the waters for the box spec discussion out there…
smile.gif

Cheers!
Martin
 

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Excellent work as always! I have wondered about this but as you say the data is not easily acquired. I would be interested in seeinghhow fan design (especially # of blades, blade design, etc) affects the PQ curve.

Again, thank you!
 

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Great exposition as always. I'm learning so much from your articles. I think any serious fan maker should provide those charts available to their consumers.
 

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Interesting and tale-tellnig as always.

On the same issue of understanding real world fan perforamnce, SPCR decided to turn away from CFM and other specs-orineted metrics, to benchmark fan efficiency on temperatures delta achieved at specific RPMs and noise levels, using a real world heatsjing (Thermalright Archon). Would you think of doing something similar for rads in the future?
 

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Glad to see this discussion one can only hope it makes a difference. For sure I'm tired of paying premium bucks for under performing fans and this article goes a long way at providing the answer to why they under perform. We need fans that get the job done not specs that wow in the end we will find them manufacturers willing or not. It's a shame we have to weed through the junk to get there doing the job that should have been done for us by those that claim to have done so. Kudos to you Martin for illuminating this much needed discussion.
 

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Discussion Starter · #8 ·
Quote:
Originally Posted by coachmark2 View Post

Hey Martin,

What simple unit of measure would you suggest to determine relative fan performance? Or is there one?
Something like "radiator mounted CFM" and "radiator mounted dbA" would be awesome but they would have to decide on a radiator or some sort of resistance standard. OR at least providing a detailed P-Q curve in a standard set of units.

Better yet, how about a thermal standard, C/W with some heat load and radiator. There are lots of ways it could be done and made useful.

I find most "better than average and industrial" fans do provide a regular P-Q curve now but they never try to compare their curves to anything. It would be nice to see some effort in comparing PQ curves at least.

Something simple like pressure at 50% max air flow would even be better that static pressure.

Realistically though, P-Q curve is an existing accepted standard, if they would just embrace that and provide it in a standard unit format, that would be a huge step forward.
 

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Discussion Starter · #9 ·
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Originally Posted by Hasdrubal View Post

Interesting and tale-tellnig as always.

On the same issue of understanding real world fan perforamnce, SPCR decided to turn away from CFM and other specs-orineted metrics, to benchmark fan efficiency on temperatures delta achieved at specific RPMs and noise levels, using a real world heatsjing (Thermalright Archon). Would you think of doing something similar for rads in the future?
Thermal is certainly the better way to go, it is just very time consuming is all. To do thermals right I find it takes a good one hour log of temps to produce one data point so to test a fan over a range of possible voltage levels could be an all weekend production to do right. That is why I have been doing CFM through a radiator. It is not as good as thermal results, but I can test one fan in 10 minutes instead of days thermal testing.

Kudos to them for doing it thermally, that is good!
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Quote:
Originally Posted by Martinm210 View Post

Something like "radiator mounted CFM" and "radiator mounted dbA" would be awesome but they would have to decide on a radiator or some sort of resistance standard. OR at least providing a detailed P-Q curve in a standard set of units.
Hardware.fr completed recently 3 large fan reviews (CFM and dBa), comparing fans on air and on a radiator (Hardware Labs SR1):
- 120 mm non-PWM fans: http://www.hardware.fr/articles/874-35/recapitulatif-db-a-vs-cfm.html
- 120 mm PWN fans: http://www.hardware.fr/articles/867-23/graphique-recapitulatif.html
- 140 mm fans (with or without PWM): http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html

As it's in French, I'll summarize the key conclusions briefly (focusing on radiator use as opposed to case fan use)
- The Gentle Typhoon is as close to the perfect 120 mm fan as possible, but is handicapped by a bearing rattle noise (also confirmed by Silent PC Review, which blames the poor quality of the fan's noise at certain speeds)
- BeQuiet! 120 are very good all rounders
- Noiseblockers PS/PL and M12 series are good all rounders and are except of any sort of parasite noise
- Nanoxia FX-Evo series are except from parasite noise and good for sub-1000RPM users
- no 140 mm fan is able to beat their reference 12o fan (BeQuiet!) on the noise/CFM benchmark, although cooling surface should also be considered
- Cougar CF-T14S et CF-V14H are more perforamnce oriented, but present a very good noise/CFM ratio
- Noctua NF-A14 FLX et NF-A15 PWM are too unstable (ie. pike frequencies based on RPM) for their own good, but can be great if the selected RPM range avoids those frequencies)
- the Corsair SP120 has poor performance and is bested by the AF series, even on radiator

Hope it will help and generate an interesting discussion thread! I for sure was surprised by the SP120 results.

If you guys are interested, I'll translate their methodology page into English for your reading over the week-end.
 

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Discussion Starter · #12 ·
Quote:
Originally Posted by Hasdrubal View Post

Hardware.fr completed recently 3 large fan reviews (CFM and dBa), comparing fans on air and on a radiator (Hardware Labs SR1):
- 120 mm non-PWM fans: http://www.hardware.fr/articles/874-35/recapitulatif-db-a-vs-cfm.html
- 120 mm PWN fans: http://www.hardware.fr/articles/867-23/graphique-recapitulatif.html
- 140 mm fans (with or without PWM): http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html

As it's in French, I'll summarize the key conclusions briefly (focusing on radiator use as opposed to case fan use)
- The Gentle Typhoon is as close to the perfect 120 mm fan as possible, but is handicapped by a bearing rattle noise (also confirmed by Silent PC Review, which blames the poor quality of the fan's noise at certain speeds)
- BeQuiet! 120 are very good all rounders
- Noiseblockers PS/PL and M12 series are good all rounders and are except of any sort of parasite noise
- Nanoxia FX-Evo series are except from parasite noise and good for sub-1000RPM users
- no 140 mm fan is able to beat their reference 12o fan (BeQuiet!) on the noise/CFM benchmark, although cooling surface should also be considered
- Cougar CF-T14S et CF-V14H are more perforamnce oriented, but present a very good noise/CFM ratio
- Noctua NF-A14 FLX et NF-A15 PWM are too unstable (ie. pike frequencies based on RPM) for their own good, but can be great if the selected RPM range avoids those frequencies)
- the Corsair SP120 has poor performance and is bested by the AF series, even on radiator

Hope it will help and generate an interesting discussion thread! I for sure was surprised by the SP120 results.

If you guys are interested, I'll translate their methodology page into English for your reading over the week-end.
Awesome, thanks for the links...looks like some great work and reading to go through ..
smile.gif
 

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Quote:
Originally Posted by Hasdrubal View Post

Hardware.fr completed recently 3 large fan reviews (CFM and dBa), comparing fans on air and on a radiator (Hardware Labs SR1):
- 120 mm non-PWM fans: http://www.hardware.fr/articles/874-35/recapitulatif-db-a-vs-cfm.html
- 120 mm PWN fans: http://www.hardware.fr/articles/867-23/graphique-recapitulatif.html
- 140 mm fans (with or without PWM): http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html
Great links Hasdrubal! I love how you can turn fans off and on in the comparison. Makes it easy to compare.

Thanks Martin for bringing this up! Great info on the fan stats. Hopefully it will make some people's decision making easier.
 

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Quote:
Originally Posted by Hasdrubal View Post

Hardware.fr completed recently 3 large fan reviews (CFM and dBa), comparing fans on air and on a radiator (Hardware Labs SR1):
- 120 mm non-PWM fans: http://www.hardware.fr/articles/874-35/recapitulatif-db-a-vs-cfm.html
- 120 mm PWN fans: http://www.hardware.fr/articles/867-23/graphique-recapitulatif.html
- 140 mm fans (with or without PWM): http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html

As it's in French, I'll summarize the key conclusions briefly (focusing on radiator use as opposed to case fan use)
- The Gentle Typhoon is as close to the perfect 120 mm fan as possible, but is handicapped by a bearing rattle noise (also confirmed by Silent PC Review, which blames the poor quality of the fan's noise at certain speeds)
- BeQuiet! 120 are very good all rounders
- Noiseblockers PS/PL and M12 series are good all rounders and are except of any sort of parasite noise
- Nanoxia FX-Evo series are except from parasite noise and good for sub-1000RPM users
- no 140 mm fan is able to beat their reference 12o fan (BeQuiet!) on the noise/CFM benchmark, although cooling surface should also be considered
- Cougar CF-T14S et CF-V14H are more perforamnce oriented, but present a very good noise/CFM ratio
- Noctua NF-A14 FLX et NF-A15 PWM are too unstable (ie. pike frequencies based on RPM) for their own good, but can be great if the selected RPM range avoids those frequencies)
- the Corsair SP120 has poor performance and is bested by the AF series, even on radiator

Hope it will help and generate an interesting discussion thread! I for sure was surprised by the SP120 results.

If you guys are interested, I'll translate their methodology page into English for your reading over the week-end.
That would be awesome Hasdrubal, I have a hard enough time with english (my native) much less french.
 

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Was faster than expected, less text that I had anticipated! Enjoy:
Quote:
In order to benchmark the different fans included in this review, we have used 2 sort of metrics:
1. Airflow, measuring that of the different models, was as an open fan, then on a Hardware Lab SR1 radiator [Hasdrubal's comment: 120.1 for 120 fans, 140.1 for 140 fans]. We used aTSI 5725 anemometer, placed at the end of 1m long/20 cm diameter PVC tube. Foams are rigged within a foam block at the other end of the tube.
Data on radiator tests are gathered using the same protocol, the fan being affixed to the rad and encased at the exit of the PVC tube. In order to minimize airleaks between the fan and radiator, we used a silicon gasket between the radiator and fan.
To ensure data consistency, airflow results are the average of 5 successive 5 seconds measurements. Fans were started 10 minutes before data was gathered.

2. Noise levels are measured using a Cirrus Optimus CR152A Class 2 sonometer. It can detect sound levels as low as 20 dB(a), at sound level that can be achieved in the room used for the benchmark.
Fans are encased within a foam block in order to minimize vibrations, and the sonometer is placed 25 cm away from the fan in order to avoid impact from the air turbulance generated bu the fan. Setting a small distance was deliberate in order to best differentiate fans throughout the benchmark.
Data on radiator tests are gathered using the same protocol, the fan being affixed to the radiator, then encased within a foam block. In order to minimize potential vibrations, we used, whenever possible (depending on the form factor of the fan frame), a slilicon gasket between the fan and the radiator. Whenever not possible, silicon spacers where used to the same effect.

A noise level in the 20 to 25 dB(A) range can be deemed silent when used within a case, but they effectively because inaudible on ly when reaching the bottom of the range. Up the 28 dB(A), cooling is very quiet, and will be qualified quiet between 28 an 31 dB(A). A dB(A) level up to 37 is considered standard for a computer, beyond cooling is noisy. Beyond 45 dB(A) the sound level becomes very noisy, and can bceome difficult to cope with unless drowned by music, altough this threshold is, as the other ones, very subjective and wil be impacted by several factors such as the auditor's sensitivity to noise, as well as the smoothness and regularity of the noise or the environment in which the computer is operated.

Fans have been fed from 2.5 to 12 V, with 0.5 V increments, using a ELC AL942 stabilised PSU, that allows for a continuous tension calibration, and delivers up to 2A, which hopefully was never required!

RPM measurements as well as PWM speeds have been gathered using a Zalman ZM-MFC3 fan controller, fed froma passive PSU in order not to add up unwanted noise.

We still gathered data using PWM fans using 3 different set speeds: 600, 900, 1200 RPM, in oredre to get an eaiser comparison, even though these 3 speeds couldn't be reached by all fans of this review when in PWM mode.
FYI, hardware.fr can be deemed one of the reference french-speaking computer fans. Their reviews and test articles aren't the most numerous ones, but certainly among the most thorough and documented ones.
 

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Quote:
And I'm not trying to pick on the Cougar fans either, I want to try some myself.
Make sure that includes the 140mm HDB. In the 120mm market, I haven't found anything to beat the AP-15 in CFM/Noise through a rad, but at 140mm the Cougar gives the AP-15 w/ adapter a run for the money. I've also been curious of a few of the more odd-ball Delta fans, but they make soooo many models and most aren't carried by normal retailers.
 

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Discussion Starter · #18 ·
Yeah, thinking of picking up some cougars. That is an impressive CFM/RPM ratio although i wonder how much loss there is with the open frame on a rad too. A lot of people seem to like them so I expect good things. I especially like the PWM control but have yet to find a fan really comparable to the GT on a rad too. GT definitely has it's own issues with harmonics too though because of those harmonic spikes they don't smoothly ramp up and down. if the cougars are good and smooth plus have PWM, they might make great fans for auto speed PWM users. I just have too many projects already..
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Hardware.info did a roundup with...I think 393 fans (80, 120, and 140mm). The Cougar 140mm was second place right behind the NZXT FX-140LB for efficiency (airflow in CFM per decibel). very impressive. I went through their list and picked out some of the top fans, calculating the efficiency.

Case Fans.txt 1k .txt file


They should have all of the original results listed in their fan database.
 

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Here is a vid detailing some more on fans. its well worth the watch for people looking for information.
 
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