Why buy low speed pwm fans when otherwise-identical high speed ones can run slow?

[shmoo]

Hey All,

I'm looking at picking up some radiator fans soon, and a lot of the pwm fans come in different speeds. In general, are the blades themselves different on these different models (same fan, different speed?) If not, why buy a low speed version when you can use PWM to run a "high speed" fan slowly? I've heard of ticking at super low speed, but tbh I don't think this happens under say 600rpm, which is already super slow...

EDIT:

I realized I may not have been very clear here. My question isn't "why use low speed fans", my questions is: If there are 2 pwm fans, for example an EK Vardar F1-120 (1150 rpm) and a Vardar F4-120 (2200 rpm):

https://www.ekwb.com/shop/ek-vardar-f1-120-1150rpm
https://www.ekwb.com/shop/ek-vardar-f4-120-2200rpm

...why buy the (slow) F1 when the the (fast) F4 is capable of spinning just as slow as the F1 all day when needed, but has the added bonus of being able to spin faster when needed...

A lot of fan companies make different versions of the same fan, which seem to look identical in every aspect except speed, and as a result different flow/pressure/noise. I MAY BE MAKING A BIG ASSUMPTION HERE in assuming that fans are otherwise the same, they look identical though... Not sure if the blades have slightly different pitches maybe? Many of the companies seem to make different versions of the same fan that run at different speeds...

Through PWM, fan speed can be controlled with a high degree of accuracy. If I can run both a slow fan and fast fan at 800rpm all day, why bother buying the slow one? The fast one can do everything the slow one can do, just as well as the slow one, but has the added bonus of being able to run faster when needed. Is there something about the faster fans that make them louder or somehow inferior to a slow fan even when both fans are operating at the same RPM??

FWIW I'm building a silent, w/c system right now. It should easily have enough radiator to keep everything very cool with slow fans, however if faster pwm fans can run slow, just as "well" as slow fans, why bother with the slow fans in the first place? A lot of the faster fans are the same exact price, and if I decide once in a blue moon that I want to go absolutely nuts with overclocking, or it's super hot in my room for some reason, with faster fans I can run them fast if I ever need to for any reason without compromising their low-speed performance.

TL;DR; 2 PWM fans, they're identical except fan A is the slow version, fan B is the fast version. Why even bother with fan A when fan B can do everything that fan A can do, just as well as fan A, plus it can spin up faster if ever needed???

 

[Rogue Leader]

depends on your case, whether you're using them on a radiator, and other factors. For example if your case has the mounts 2-3 low speed PWM fans can move just as much air or more than one high speed one, quieter.

 

[Virtual_Singularity]

Shmoo, in regards to those rad fans you mentioned, it comes down to the noise & preference. Rogue Leader's reply describes the issue well enough. Noise has become nearly as important a consideration for many system builders, regardless whether they use AIO cooling, custom loops, or even air.

To elaborate: For water cooling, fans able to deliver adequate static pressure for their radiators while maintaining low noise levels are ideal. Depending on case size, rad size & number of rads used, overclocking, ambient temps, & whatever other variables I might've left out, some would prefer quieter PWM fans with lower RPM, or vice versa. For example, some may choose a large case for their overclocked custom loop build, along with 2 or even more rads, opting to use several low RPM fans & achieving an impressively low noise level. It really comes down to budget & personal preference. The reddit link deals with the same issue. https://www.reddit.com/r/watercooling/comments/5obk36/how_to_achieve_lowest_fan_rpm/

 

[sirstinky]

PWM fans are able to increase or decrease their speed based on certain conditions like temperature, so the real thing to consider is how loud the fan is when it's spun up to it's highest RPM. Take the Intel stock coolers- they are really quiet at idle when spinning at 1000 rpm, but when the motherboard says the CPU is loaded up and the fan spins faster, it generates more noise. Big fans can move a lot of air at low speeds. Smaller ones need to spin faster to move the same amount of air, and make more noise in the process. The blade design/shape, the fan housing, the motor, position (pressed flat against a rad or case will cause drag and make more noise) and the rated RPM all play into how much noise the fan makes. As far as "ticking" generally a good quality fan with hydraulic bearings is pretty quiet.

 

[shmoo]

PWM fans are able to increase or decrease their speed based on certain conditions like temperature, so the real thing to consider is how loud the fan is when it's spun up to it's highest RPM. Take the Intel stock coolers- they are really quiet at idle when spinning at 1000 rpm, but when the motherboard says the CPU is loaded up and the fan spins faster, it generates more noise. Big fans can move a lot of air at low speeds. Smaller ones need to spin faster to move the same amount of air, and make more noise in the process. The blade design/shape, the fan housing, the motor, position (pressed flat against a rad or case will cause drag and make more noise) and the rated RPM all play into how much noise the fan makes. As far as "ticking" generally a good quality fan with hydraulic bearings is pretty quiet.

Shmoo, in regards to those rad fans you mentioned, it comes down to the noise & preference. Rogue Leader's reply describes the issue well enough. Noise has become nearly as important a consideration for many system builders, regardless whether they use AIO cooling, custom loops, or even air.

To elaborate: For water cooling, fans able to deliver adequate static pressure for their radiators while maintaining low noise levels are ideal. Depending on case size, rad size & number of rads used, overclocking, ambient temps, & whatever other variables I might've left out, some would prefer quieter PWM fans with lower RPM, or vice versa. For example, some may choose a large case for their overclocked custom loop build, along with 2 or even more rads, opting to use several low RPM fans & achieving an impressively low noise level. It really comes down to budget & personal preference. The reddit link deals with the same issue. https://www.reddit.com/r/watercooling/comments/5obk36/h...

depends on your case, whether you're using them on a radiator, and other factors. For example if your case has the mounts 2-3 low speed PWM fans can move just as much air or more than one high speed one, quieter.

Hey I wasn't super clear with my question, so I updated the thread title and my initial post to clarify my question. Sorry about that everybody!

 

[Virtual_Singularity]

"...why buy the (slow) F1 when the the (fast) F4 is capable of spinning just as slow as the F1 all day when needed, but has the added bonus of being able to spin faster when needed... TL;DR; 2 PWM fans, they're identical except fan A is the slow version, fan B is the fast version. Why even bother with fan A when fan B can do everything that fan A can do, just as well as fan A, plus it can spin up faster if ever needed??? "


Ultimately: noise factor, system needs, & personal preference. Looking at the charts, the F4 will still be somewhat louder than the F1, even at lower airflow & RPM's. There's power draw to consider (likely negligible for most people), & static pressure/airflow differences as well, & what you feel suits you better. If you've radiators suited to the less powerful & quieter F1 for your loop, are able to maintain temps & noise levels you're satisfied with, that's a good reason to choose the F1.

If the more powerful F4, or the even more powerful FF5 @ 3000rpm, & same price as the F4 ($3 more than the F1), suit your needs better, then the F4 or FF5 would be the better choice for performance overall, and if noise isn't a primary concern. If it were me, I'd choose the F1's as long as they suit the needs of your system & offer adequate overall performance.

 

[varis]

Will the fans fail to start if voltage is too low? Or most people simply don't want to bother with aftermarket modifications for their fans? (I never did over 6+ years even though I have the skills and pretty good tools to modify the stuff.)

 

[Dean Simmons]

While I am not sure If this applies to your particular fan model, what I've noticed is that their power ratings tends to hint at a fans lowest potential speed, (without hardware modifications) and this usually means that The lower rated fan will spin more slowly at idle than the one that is rated for more.

Hope that helps. = )

I don't know if hardware modifications such as soldering a resistor to the fans positive (+ red) power line will work, (I've not tried it myself) but the general consensus is that PWM fans will only tolerate a minimum operating voltage before they stop working, so we have to experiment with each model and see it's limits to see if we can make our (noisy) PWM fans more quiet. = )

 

[USAFRet]

While I am not sure If this applies

5 years later....

Please don't dredge up ancient threads.