Mixing PWM & DC fans

[Lee989]

Sorry in advance for any stupid questions! Just trying to avoid doing anything wrong

 

I've just ordered a Fractal Design Meshify C Mini for my build, it includes two 120mm fans that have 3-pin connectors (so they must be DC controlled right?). I've read a lot of reviews and it seems common to swap the included intake for 2 x 140mm fans to either get better airflow and/or reduce noise (be quite pure wings 2 are very popular). Oddly the PWM variants of these are slightly cheaper in the UK than the DC variants. 
 

I haven't bought a mobo yet, but i'm planning on the MSI B450 Mortar Max. In the manual I see it supports both DC and PWM fan types and supposedly does "automatic detection" but you can also manually set the mode in the BIOS.

 

So on to my questions:

 

1. Should I be mixing PWM and DC fans?

2. If not, should I throw out both pre-installed DC fans and go PWM, or keep the pre-installed and get 2 new 140mm DC?

3. If "automatic detection" doesn't work for some reason, can I set the PWM/DC setting for each header, or is it a single setting for all headers?

4. Assuming I keep the pre-installed fans, I'd have 2 x 140mm intake, 1 x 120mm rear exhaust. Would you use the remaining 120mm as a bottom intake or put it at the top rear (or top center) to help exhaust? (or don't use it at all?).

4a. Guessing I'd need to get a fan splitter for the 2 front intakes as I only have 3 headers?

5. Is there a strong argument to leave it "stock" and see what the temps are like? I guess I could wait and see if I need any extra fans?

 

By the way, the case will be sat on my desk close to me, so whilst i'm not expecting to get a "silent" build, I am trying to keep fan noise down as much as possible within reasonable costs.

 

Thanks in advance

 

 

 

[Mira Yurizaki]

Rather than answer each question you had individually, I'll try to go for the general approach. You can mix and match fans all day, the system won't care. The only problem with Non-PWM fans is they can't "spin-down" slower than PWM fans due to a minimum voltage required to even turn the motor.

 

So it's more of a question of finding that bare minimum point and seeing if keeping it there still generates too much noise for you.

[Lee989]

Thanks @Mira Yurizaki 

 

So since I can mix, better off going for the PWM ones anyway as they can spin down slower. Then I guess I try out the 2 x 120mm's that are non-PWM and see how loud they are on their slowest setting and if they are too loud I switch those out for PWM also to get them even slower/quieter.

 

And If i want to use all 4 fans with the 3 mobo fan headers, I will use a PWM fan splitter on the 2 front intakes.

 

Hopefully I understood you correctly   Thank you for your reply

[LogicalDrm]

As said, as long as you don't mix them in one header, it doesn't matter. Like my case fans are 3pin and CPU has PWM. All are controlled with SpeedFan (I have older mobo), so I can go to 30% with 3pins and 0rpm with CPU fans.

 

You can see options for header control from BIOS. I recommend getting familiar with BIOS overall.

[Lee989]

@LogicalDrm Thanks.

 

Last time I looked at a BIOS screen myself was nearly 10 years ago. Once I get all the parts ordered and assembled I'll be able to take a look. I'm sure it's obvious when you look at it, I just over-prepare for everything

 

[WoodenMarker]

As mentioned, don't mix fans on a single header unless you don't mind using dc for all fans or having no fan control. 

Auto picks one setting -- either pwm or dc.

With dc, the voltage is variable and can be used to control rpm. 

With pwm, fans receive 12v on the 2nd pin. The 4th pin is for pwm which modulates the incoming 12v to control fan speed. 2-3pin fans don't have this 4th pin nor the pwm ic so they just receive 12v and run at 100% rpm.

Power fans however you'd like. As long as temps are fine and you're not bothered by the noise, all is fine.