[SOLVED] What max rpm is good for case fans?

[Bofibofi]

I'm thinking of buying a couple of be quiet shadow wings 2 (140mm PWM) for my rig, because i really want my fans to be as quiet as possible, however i noticed that their max rpm is 900, which seems to be quite a bit lower than other fans. I'm wondering if these fans are any good or if I should opt for some fans with a higher max rpm.
Btw, my system atm runs fine (motherboard temps around 30-40C) with DC controlled fans but their lowest duty cycle is at 60% = really loud all the time.
Thanks for any help!

 

[Phaaze88]

Depends on your system specs.
Running any high powered parts in there? Any overclocks?
With a silence-focused build, there is a sacrifice in cooling performance. There are fans that do both, they're more of a jack-of-all-trades, but you'll obviously pay for that kind of performance.

If your build consists of say, a 9700k and a 2080 Super, you can expect a case full of those fans to be running at max most of the time, save for idling on the desktop.
Lower rpm fans don't have much flexibility in the way of adjustable fan curves.

 

[Remeca]

The rpm isn't the whole story on how much air a fan can move. Quiet fans are designed to move more air at less rpms, so just read the specs on your fans, and compare how much air they move at what rpms, and settle for an acceptable amount of air flow at a noise level you're comfortable with.

 

[Bofibofi]

Depends on your system specs.
Running any high powered parts in there? Any overclocks?
With a silence-focused build, there is a sacrifice in cooling performance. There are fans that do both, they're more of a jack-of-all-trades, but you'll obviously pay for that kind of performance.

If your build consists of say, a 9700k and a 2080 Super, you can expect a case full of those fans to be running at max most of the time, save for idling on the desktop.
Lower rpm fans don't have much flexibility in the way of adjustable fan curves.

I'm running an 8700k overclocked to 4.7 Ghz, 1.28V. I've had no problems with cooling my CPU. My Nzxt Kraken x62 is working great with PWM, manual fan curve. CPU is never above 75C even at very high load. My rog strix 2080 is also working fine by it self sitting at 50-60C at full load. Motherboard never going over 40C. My build is inside the define s2 which has three 140mm included fans all set to exhaust (intake is through my krakens radiatior). So my ultimate goal here is to lower noise as much as possible, mostly when idling, because the preincluded fans are quite loud even at 60% duty cycle. If you think that the shadow wings aren't powerful enough, could you suggest some alternatives that might suit my needs? Thx a lot.

 

[digitalgriffin]

I'm thinking of buying a couple of be quiet shadow wings 2 (140mm PWM) for my rig, because i really want my fans to be as quiet as possible, however i noticed that their max rpm is 900, which seems to be quite a bit lower than other fans. I'm wondering if these fans are any good or if I should opt for some fans with a higher max rpm.
Btw, my system atm runs fine (motherboard temps around 30-40C) with DC controlled fans but their lowest duty cycle is at 60% = really loud all the time.
Thanks for any help!

That explains why they are quiet. The probably have piss pot poor air flow and pressure measurements too. My advice: Stay away.

It's always easier to throttle down a fan to lower noise than it is to get more airflow out of a fan that's already maxed out.

The type of fan you buy should be based on your case and where/how they are used and how many you wish to use. Other factors include what kind of cooling you are using for your CPU/GPU.

If you have a radiator or heavy filter, I would use a pressure/balanced based fan. If you have a mostly clear inlet/exhaust, I would use an airflow fan.

You CAN double the amount of fans. This would mean you would need only 1/2 the airflow from each. Noise is an exponential function of flow rate + bearing noise. So you could cut your airflow noise down by MORE than half for each fan by doubling the fans. But you still have to deal with bearing noise. A quality bearing here is important when taking this approach. (Double ball bearing, or mag lev)

 

[scout_03]

see these higher cfm with mode speed option https://cougargaming.com/products/cooling/vortex_pwm_fan/

 

[Karadjgne]

Fans are a function of design. Higher speed, higher cfm fans will have a shorter width blade set at a higher pitch, like the Noctua S series. Higher pressure for the ans will have a fat blade at a lower pitch, like the Noctua F. A balanced fan will be a compromise of both, like the Noctua A25. Rpm has little to do with actual performance, its just a measure of the range of performance, you can get the same performance from a well designed fan at 1000rpm as a piss poor fan at 2000rpm.

An object moving through air creates sound. No avoiding that little fact. That sound can come from various sources like bearings, harmonics, pitch, balance, rpm etc. Some fans have notches or addional vanes on the blades in order to create more sound, at an opposing harmonic, which negates those frequencies and ends up quieter as a result. Usually around about 900ish rpm, fans will create enough noise to be somewhat audible, and the higher the rpm, the louder that gets. If you've ever heard an 8000rpm Delta server fan, you'd understand.

There is no 'one size fits all' case fan. Each fan has slightly different properties and each case has slightly different attributes, the trick being to find which works best. Just as @digitalgriffin suggested. It's a balancing act between what you need, what you want and what you can live with.

 

[Bofibofi]

That explains why they are quiet. The probably have piss pot poor air flow and pressure measurements too. My advice: Stay away.

It's always easier to throttle down a fan to lower noise than it is to get more airflow out of a fan that's already maxed out.

The type of fan you buy should be based on your case and where/how they are used and how many you wish to use. Other factors include what kind of cooling you are using for your CPU/GPU.

If you have a radiator or heavy filter, I would use a pressure/balanced based fan. If you have a mostly clear inlet/exhaust, I would use an airflow fan.

You CAN double the amount of fans. This would mean you would need only 1/2 the airflow from each. Noise is an exponential function of flow rate + bearing noise. So you could cut your airflow noise down by MORE than half for each fan by doubling the fans. But you still have to deal with bearing noise. A quality bearing here is important when taking this approach. (Double ball bearing, or mag lev)

Tanks, your answer clears things up a bit. I don’t think I can go for more than 3 case fans in my build as you were talking about. Please see my specifications and how my fans are currently set up in my answer to Phaaze. But going for fans with a bit higher rpm and especially looking at fans with different cfm:s.
Thanks

 

[Bofibofi]

Fans are a function of design. Higher speed, higher cfm fans will have a shorter width blade set at a higher pitch, like the Noctua S series. Higher pressure for the ans will have a fat blade at a lower pitch, like the Noctua F. A balanced fan will be a compromise of both, like the Noctua A25. Rpm has little to do with actual performance, its just a measure of the range of performance, you can get the same performance from a well designed fan at 1000rpm as a piss poor fan at 2000rpm.

An object moving through air creates sound. No avoiding that little fact. That sound can come from various sources like bearings, harmonics, pitch, balance, rpm etc. Some fans have notches or addional vanes on the blades in order to create more sound, at an opposing harmonic, which negates those frequencies and ends up quieter as a result. Usually around about 900ish rpm, fans will create enough noise to be somewhat audible, and the higher the rpm, the louder that gets. If you've ever heard an 8000rpm Delta server fan, you'd understand.

There is no 'one size fits all' case fan. Each fan has slightly different properties and each case has slightly different attributes, the trick being to find which works best. Just as @digitalgriffin suggested. It's a balancing act between what you need, what you want and what you can live with.

Ok, thanks for clarification! What kind of bearings do you think I should go for if I’m looking for 3 exhaust case fans? Also what should I focus more on, high airflow fans or high pressure fans for my build? You can see my specs in my answer to Phaaze. Any help would be greatly appreciated since I’m still quite lost when it comes to choosing for myself. Thanks a lot!

 

[digitalgriffin]

Tanks, your answer clears things up a bit. I don’t think I can go for more than 3 case fans in my build as you were talking about. Please see my specifications and how my fans are currently set up in my answer to Phaaze. But going for fans with a bit higher rpm and especially looking at fans with different cfm:s.
Thanks

So most of your noise is coming from the Kraken X62. If you are looking to replace those then you need 140mm fans.

Turn up the pump to 100%. If possible make the radiator fresh intake air. Then slowly crank the Fans.

If looks aren't important, I can whole heartily recommend the Noctua 140mm's.

NF-A14 PWM (About $22->$25/fan) They have decent static pressure, flow and use a combination HDB bearing + mag lev for the end bearing.

 

[Bofibofi]

So most of your noise is coming from the Kraken X62. If you are looking to replace those then you need 140mm fans.

Turn up the pump to 100%. If possible make the radiator fresh intake air. Then slowly crank the Fans.

If looks aren't important, I can whole heartily recommend the Noctua 140mm's.

NF-A14 PWM (About $22->$25/fan) They have decent static pressure, flow and use a combination HDB bearing + mag lev for the end bearing.

Oh, is it the included fans with the kraken that are making all the noise. I guess I should have looked into that. I was sure it were my case fans that were making all the noise at constant 60%+ duty cycle. Well in that case, I’ll just swap out the fans for my radiator as you said. Those Noctua fans seem nice, and I looks wont matter, since they’ll be hidden between the radiator and front panel.
One question though; what do you mean by making the radiator fresh intake air and cranking up the fans?

 

[Karadjgne]

If using Cam, tge kraken should be on silent mode, not standard or performance. With my x61 there was only a 4°C difference under load, but a considerable difference in volume. You can also set it to respond to coolant temps, not cpu temps which does wonders for idle when Windows does its normal 50° bounces.

Exhausts have nothing really behind them but open space, so higher airflow fans work better, as long as there's still some sp to get that air through the grill. Intakes are usually better as balanced or pressure, depending on if there is hdd bays, bunch of wiring, thick dust screens etc

 

[digitalgriffin]

Oh, is it the included fans with the kraken that are making all the noise. I guess I should have looked into that. I was sure it were my case fans that were making all the noise at constant 60%+ duty cycle. Well in that case, I’ll just swap out the fans for my radiator as you said. Those Noctua fans seem nice, and I looks wont matter, since they’ll be hidden between the radiator and front panel.
One question though; what do you mean by making the radiator fresh intake air and cranking up the fans?

It could be the case fans. But balanced based radiator fans have a tendency to be more noisy because they have to generate more pressure and maintain a decent airflow. So I'm taking an educated guess. One way to tell is to adjust Fan profiles in BIOS or in software and listen.

Maintaining a high flow rate (pump RPM) is the best performance gain for radiators (up to a point) due to Newtons law of cooling/heating. So if you were to pick one, pick pump flow rate over fan rate increases. As this is a more efficient approach you'll have to crank the fans less. Pumps are relatively silent, fans are not. I keep my pump at ~70%->80% and quickly crank it to 100% under load.

Intake air is always cooler than exhaust air. So pulling outside air in through the radiator is preferable to pushing warmed case exhaust air out through the radiator. Again, this is because Newtons law of cooling. The greater the temperature delta between the AIO fluid and the surrounding air, the greater energy exchanged (again up to a point)

It's actually a very very complex differential equation formulation that takes many parameters and iterations into account from radiator shape, size, flow rate, incoming air temp, face velocity, radiator depth, rows of tubes, tubes per circuit, air density, relative humidity, fluid temp, fluid type, fan thickness, fins per inch, fin material, pipe material, pipe thickness so on and so on.

 

[Bofibofi]

It could be the case fans. But balanced based radiator fans have a tendency to be more noisy because they have to generate more pressure and maintain a decent airflow. So I'm taking an educated guess. One way to tell is to adjust Fan profiles in BIOS or in software and listen.

Maintaining a high flow rate (pump RPM) is the best performance gain for radiators (up to a point) due to Newtons law of cooling/heating. So if you were to pick one, pick pump flow rate over fan rate increases. As this is a more efficient approach you'll have to crank the fans less. Pumps are relatively silent, fans are not. I keep my pump at ~70%->80% and quickly crank it to 100% under load.

Intake air is always cooler than exhaust air. So pulling outside air in through the radiator is preferable to pushing warmed case exhaust air out through the radiator. Again, this is because Newtons law of cooling. The greater the temperature delta between the AIO fluid and the surrounding air, the greater energy exchanged (again up to a point)

Thanks for your help! I’ll check tomorrow which fans make the most noise. If it’s the intake fans as you are suggesting, I’ll go for two of those Noctua fans. They seem to fit my needs. I’ll try putting more juice into the pump as opposed to the fans. Again, thanks for all the tips!

 

[Bofibofi]

If using Cam, tge kraken should be on silent mode, not standard or performance. With my x61 there was only a 4°C difference under load, but a considerable difference in volume. You can also set it to respond to coolant temps, not cpu temps which does wonders for idle when Windows does its normal 50° bounces.

Exhausts have nothing really behind them but open space, so higher airflow fans work better, as long as there's still some sp to get that air through the grill. Intakes are usually better as balanced or pressure, depending on if there is hdd bays, bunch of wiring, thick dust screens etc

I haven’t really been able to use cam for controlling the fans or pump. Don’t know if it has to do with how I have it all connected to the motherboard or something else. I’ve been setting up fan curves and pump curve through the bios.

 

[Karadjgne]

Ahh. That doesn't work so well as Cam. I set mine for silent and pretty much forgot it existed for the next 6 years, always had good temps, even at 4.9GHz on my i7-3770K and never gave me a lick of trouble. Except when I switched to win10 and the stupid User crap thing, but that was an easy task fix. Sometimes needed a reinstall after major windows update, but so do many programs that work with bios settings.

Setup was easy. Fans go to pump. Pump goes to cpu_fan header, Sata power and usb2 port. Simple. Gives full pump/fan control, halfway decent dashboard, control of pump rgb.

One thing about Cam though, and there are some ppl who seriously don't like it for only this reason, nzxt like to actually improve their software and stay on top of issues. To do that, it gathers your pc info, like cpu, ram, speeds, load % etc and compares that with pump/fan speeds and settings and sends that info to nzxt for study. Some see that as to close to being a Trojan or malware or an invasion of privacy etc. To me it's no big deal. It's not info that's sold to others, it's used In house, there's no names or IP's or any personal info, it's all stuff Microsoft, Google and half a dozen others already have or have access to.

 

[Karadjgne]

There's one thing many ppl don't get about aios. When it comes to temps, they are the same as a full custom loop, not an aircooler. Liquids have a massive ability to absorb heat, and don't really need to respond to cpu temps. Cpu temps are the temp that's left after the pump head has absorbed any excess wattage. Aircoolers are a metal block and heatpipes attached directly to the cpu, so need to respond immediately to cpu temps as metals don't absorb heat as much as transfer it. Cpu temps are a result of the efficiency of the cooler to transfer the heat from the IHS to the fins for dissipation.

I'm much more inclined to have faith in a cooler that runs a constant 50-60°C under any loads, than a cooler that bounces between 30 and 80°C depending on the load, never knowing if a load is too much.

 

[Bofibofi]

Ahh. That doesn't work so well as Cam. I set mine for silent and pretty much forgot it existed for the next 6 years, always had good temps, even at 4.9GHz on my i7-3770K and never gave me a lick of trouble. Except when I switched to win10 and the stupid User crap thing, but that was an easy task fix. Sometimes needed a reinstall after major windows update, but so do many programs that work with bios settings.

Setup was easy. Fans go to pump. Pump goes to cpu_fan header, Sata power and usb2 port. Simple. Gives full pump/fan control, halfway decent dashboard, control of pump rgb.

One thing about Cam though, and there are some ppl who seriously don't like it for only this reason, nzxt like to actually improve their software and stay on top of issues. To do that, it gathers your pc info, like cpu, ram, speeds, load % etc and compares that with pump/fan speeds and settings and sends that info to nzxt for study. Some see that as to close to being a Trojan or malware or an invasion of privacy etc. To me it's no big deal. It's not info that's sold to others, it's used In house, there's no names or IP's or any personal info, it's all stuff Microsoft, Google and half a dozen others already have or have access to.

Perfect, thank you very much! I’ll wire it like you describe and reinstall the program. This will help out a lot if I get cam to work.

 

[Karadjgne]

Sure, no worries. It's better if you do run Cam, especially since the nzxt Krakens series use a variable speed pump. The programming knows when to increase pump speed and when it doesn't need to, which a bios set curve won't respond to appropriately, so you end up with the wrong flow volume almost always. Which is an issue since coolant volume over the cpu determines the temp, which determines the fan speeds. The coolant temps are highly different to cpu temps. You can run a cpu at 70°C no issues, but the amount of wattage it would take to get the coolant to anything above 50°C is simply massive. It'd take something like a i9 9900k or FX 9590 running Prime95 full core turbo a half an hour to get that. My x61 fans never went above 700rpm unless I stress tested, usually staying in the 540-600 range, pretty much silent.