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Is there a reason to get Voltage over PWM?

4K views 34 replies 13 participants last post by  doyll 
#1 ·
#2 ·
If using a fan controller then voltage, if using pwm mobo (if its a true pwm fan header) then pwm. Supposedly its bad to control pwm fans with voltage control.

My spare hp had the cpu fan stop working, testing it i found out that it was working but the pwm circuitry probably wasnt anymore so i unplugged that pin and run it power/ground/sense.
 
#3 ·
Quote:
Originally Posted by bluej511 View Post

If using a fan controller then voltage, if using pwm mobo (if its a true pwm fan header) then pwm. Supposedly its bad to control pwm fans with voltage control.

My spare hp had the cpu fan stop working, testing it i found out that it was working but the pwm circuitry probably wasnt anymore so i unplugged that pin and run it power/ground/sense.
I'm using an asus z170 pro gaming and it says all the headers are pwm.
 
#4 ·
#5 ·
PWM and Voltage are technically equal to each other imho.
Both have their advantages, but they only work as good as your controller is. You should always proceed from your controller that can either handle 3-Pin Voltage or 4-Pin PWM or even both. And keep in mind that there are some vendors (mostly MSI and Gigabyte) with "fake" 4-pin headers that can only provide voltage regulation.

Regarding min. RPM:
PWM is not necessarily superior in this categorie because it always depends on A) how good the fan and B) how good your controller is (how wide the range is you can lower the voltage or PWM in %). Since I have tested a lot of fans on my Aquaero 5 I can say that most of the voltage fans (even very cheap models) can be throttled down to 3,0 to 3,5 volts(!) whilst PWM fans do have varying ranges from about 45% to 20% in the best cases.

That said PWM has the inherent risk of suffering from commutation noise which expresses itself in a rattling bearing noise. Such issues can appear when the constant shifting between 0V and 12V of an (unsmoothed!) squarewave signal genereate cyclic, fitful impulses of the blade. This phenomenon will not appear with a constant voltage.

But in the end it all depens on the quality and features of the fan and the controller being used to power it.
 
#6 ·
PWM is better and a more efficient use of energy / power, when it is done properly.
  • PWM uses pulsed power while variable voltage generates heat reducing the voltage from it's source 12v.
  • PWM has the ability to run at lower speeds than variable voltage because it generates full torque every time power is applied (which can sometimes create the clicks and rattle).
The above are the reason industrial motors are now mostly PWM and not variabable voltage.

I agree with Dr Strangelove, PWM is only as good as the PWM controllers, but there are 2 control components involved; the one built into the fan and the one fan plugs into.

While computation noise can be a problem, the power pulses can be done so there is no noise .. be it in the bearings, fan blade vibration, power surge, etc. As Dr S says, it's not a problem if the start/stop pulse is rounded,

PWM fans will also run with lower than 12v power, which means they will run at a correspondingly lower RPM range.

I guess TY-147A is a one of these 'best cases', because it's PWM control is from just under 300rpm to 1300rpm.
tongue.gif


The short answer,PWM is preferable, but it really on what your computer system can properly control .. and what what the fan prices are.
 
#7 ·
#8 ·
Quote:
Originally Posted by Tylerr View Post

Yeah i know about that, although when you buy 2 of the other ones it only comes out to about $4 more.
Shop around, prices vary a lot between retailer. Phanteks site sells too and sometimes have some good package deals.

Have you looked at the PH-F140MP? It's really a good fan too.
 
#10 ·
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#11 ·
Quote:
Originally Posted by doyll View Post

Phanteks site sells too and sometimes have some good package deals.

Have you looked at the PH-F140MP? It's really a good fan too.
You're right. Can get a 2 pack of PH-F140SP for $24.99 directly from phanteksusa.

they only sell the MP in 1\4\6 packs though, no 2.

though i'm not sure how much shipping will cost...
 
#12 ·
Quote:
Originally Posted by Tylerr View Post

You're right. Can get a 2 pack of PH-F140SP for $24.99 directly from phanteksusa.

they only sell the MP in 1\4\6 packs though, no 2.

though i'm not sure how much shipping will cost...
Give them a call and ask about getting a 2 pack added to the list.
biggrin.gif
 
#14 ·
Quote:
Originally Posted by Tylerr View Post

eh with $7 shipping it comes out to near the same price as newegg.
Yeah, but shopping around is the key. Did you check Amazon? Sometimes their sellers are low priced too. Even some of the big Ebay sellers are good sources.
 
#15 ·
Quote:
Originally Posted by outofmyheadyo View Post

Sorry for the OT but as asus only gives us true pwm on cpu and cpu_opt is there another manufacturer that has true pwm on all the fan headers on the mb, since I fail to see the point of other headers if u cant control em to your desire.
My board has PWM on all of its headers. The quality of the controller is questionable, but it's there.
 
#16 ·
Quote:
Originally Posted by Loladinas View Post

My board has PWM on all of its headers. The quality of the controller is questionable, but it's there.
Really depends on the board, the high ends ones def do but id imagine most mobos with 4 pin headers arent going to be pwm. Ive got 2 cpu ones that are pwm and 3-4 4pin headers that aren't.

Ive dug deep into a few mobo manuals and most wont even tell you haha.
 
#17 ·
Quote:
Originally Posted by Tylerr View Post

If 2 140mm fans are priced the same and the only difference is pwm or voltage control is there any reason to go for the voltage one over the pwm?

these are the fans:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835709023
http://www.newegg.com/Product/Product.aspx?Item=N82E16835709022
Depends on a fan, some fans like to click more when controlled with the other method than for which they were designed but of course it can also be the other way around.
Some mobos have hybrid control depending on what you connect or set the header to.
In general PWM is more noisy electrically and also acoustically depending on how fast the PWM is.

Overall, buy the fan that your mobo header supports. If you are in doubt you have to check for the ICs near the header and decode it from specs of those chip to see what they are and can do PWM or voltage control or both, how much load they can handle etc.

My ASRock board has a mix of 4 pin PWM headers and 3 pin voltage controlled headers plus a 3 pin header that is 12V constant not controllable.
 
#18 ·
For many people the best way to check if a motherboard fan header is PWM is to to make a simple splitter with 12v & ground to PSU power and a 4pin fan plug with PWM & RPM leads


Sadly, even the motherboard specifications and manuals misrepresent fan headers. Asus flat out lied saying 4-pin headers were PWM .. and continued to even after users used simple testing like about to prove they were not.
PWM fans plugs always have 12v power .. it never stops and it never goes to lower voltage.
So if we supply the fan with a PWM control signal from motherboard set at a lower speed the fan will not be running full speed.
If the fan runs at full speed, it is not getting a PWM signal or the signal is telling it to run full speed.

We can get more involved in the technical aspects of how PWM signal power and control works, but that is a big bucket of squirming techical worms I'm not even sure how exactly works.
 
#19 ·
Quote:
Originally Posted by outofmyheadyo View Post

Sorry for the OT but as asus only gives us true pwm on cpu and cpu_opt is there another manufacturer that has true pwm on all the fan headers on the mb, since I fail to see the point of other headers if u cant control em to your desire.
Actually, it depends on the particular board. Many of the ASUS boards are true PWM throughout. As far as other mfg, I see ASUS as having the most PWM support on chassis headers.
 
#20 ·
Just "having" PWM support is not a free ticket for an unrestricted control of the fan btw.
It all comes down to what the controller can finally handle. When there is a limit of min. 40% and you have a high RPM fan (which is often the case for PWM ones) but want to drive it on extra low speed you are possibly stranded.

Just had such issues on my old Hero VI which coudln't throttle my voltage regulated iPPCs (I know, shame on my for buying an industrial fan) under 800 RPM. And on my newer Z170M Mortar from MSI the min. percantage for the sys fans is even on 50%!

Its a "nice to have" owning fans that have very low minimum speed. But in the end actually the mobo is the bottle neck in a lot of threads where users complain about bad fan controls because the vendors just don't invest anything in realiable ICs or even a working software.

One more reason to go for a separate fan controller, such as an Aquaero in my case which is a really powerful gadget.
 
#21 ·
Quote:
Originally Posted by Dr Strangelove View Post

Just "having" PWM support is not a free ticket for an unrestricted control of the fan btw.
It all comes down to what the controller can finally handle. When there is a limit of min. 40% and you have a high RPM fan (which is often the case for PWM ones) but want to drive it on extra low speed you are possibly stranded.

Just had such issues on my old Hero VI which coudln't throttle my voltage regulated iPPCs (I know, shame on my for buying an industrial fan) under 800 RPM. And on my newer Z170M Mortar from MSI the min. percantage for the sys fans is even on 50%!

Its a "nice to have" owning fans that have very low minimum speed. But in the end actually the mobo is the bottle neck in a lot of threads where users complain about bad fan controls because the vendors just don't invest anything in realiable ICs or even a working software.

One more reason to go for a separate fan controller, such as an Aquaero in my case which is a really powerful gadget.
Noctua's tech department states that the iPPCs won't run under 800 rpm on voltage regardless of the controller.
 
#23 ·
Quote:
Originally Posted by Dr Strangelove View Post

Just "having" PWM support is not a free ticket for an unrestricted control of the fan btw.
It all comes down to what the controller can finally handle. When there is a limit of min. 40% and you have a high RPM fan (which is often the case for PWM ones) but want to drive it on extra low speed you are possibly stranded.

Just had such issues on my old Hero VI which coudln't throttle my voltage regulated iPPCs (I know, shame on my for buying an industrial fan) under 800 RPM. And on my newer Z170M Mortar from MSI the min. percantage for the sys fans is even on 50%!

Its a "nice to have" owning fans that have very low minimum speed. But in the end actually the mobo is the bottle neck in a lot of threads where users complain about bad fan controls because the vendors just don't invest anything in realiable ICs or even a working software.

One more reason to go for a separate fan controller, such as an Aquaero in my case which is a really powerful gadget.
Well said!
thumb.gif


I use an Aquaero 5 for most of my fan testing, both voltage and PWM. Fans will perform great! But plug them into a build using motherboard control and they often act completely different.
 
#24 ·
I am running two Noctua NF-A14 ULN's for front intake fan. Open Monitor says they are running at 750 rpm each. When I run them with LNA's they run about 600 rpm each.

These are fixed-speed fans. If you want variable-speed fans, go with PWM. The only question is Are the PWM circuits silent?

I use Gigabyte boards. The Z87 and Z97 boards have four PWM headers, a CPU, a CPU_OPT, SYS_1 and SYS_2. SYS_3 is a fixed-voltage fan header.

Basically, you buy a voltage-controlled fan for your case if you don't expect to vary the speeds. Buy a fan which runs the right speed and puts out the right amount of airflow and makes the right amount of noise. Then you forget about it, unless you live in a dusty place and you have to clean the filters and the fans.

If you expect to vary the speeds of the case fans, get PWM fans, and either put them in PWM headers or put them in a PWM splitter.
 
#25 ·
Iirc, Asus header can control both type of fan since hasewell refresh, where asrock adapt that on skylake. The main advantage of voltage fan is probably the use of "legacy" fan like the gentle typhoon or s flex. Some pwm fan cannot stop spinning completely, where all proper voltage fan on voltage header can do(may require speed fan what not), making it semi passive. So if you run 24/7, it can slow down dust accumulation.

Sent from my XT1575 using Tapatalk
 
#26 ·
As I've already posted before in some of the threads PWM isn't the end all be all. With the fans I use, on the motherboard I use them, voltage control gives me both, a wider RPM range (~250-2400 vs. ~600-2400) and quieter operation. PWM clicks at low speeds, but I believe that's a quirk of my motherboard.
 
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