How do PWM fans and fan controllers work?
I'm planning on getting 3x Silent Wings 3 fans in the high speed variant which would be front mounted on my Noctis 450. But then something struck me, will the lower speed fans make the high RPM fans slow down? Or do PWM fans distribute the speed as things like 50% of total speed? Also, I've noticed that the fan hub on the back of the mobo has only 3 pin connectors for the fans, so will I be able to use non-PWM fans and still have control of their speed?
a good quality one is connected to the sys_fan header, via that connection it receives orders from the mainboard but it doesn't take power from the sys_fan, it takes power from a molex cable or a sata power cable from the psu
the system will see it as a single fan, will order it to spin up or down, the fans will just follow orders the best they can, this is where the quality of the fans matter the most
the fans do get orders via the third pin, it makes them spin slower or faster, if for some reason you need to connect a 3 pin fan to a molex connector, it just uses 2 pins, the fan will spin at full speed, instead by following orders of spin half speed via the third pin
there is some headers that do not use the sys_fan cable at all, so you just push buttons to move between 4 states, off, low, medium and high, to set the speeds by yourself
about the fans with different connectors, if some are molex, those can't go into the fan header, if those are 4 pin fans and you have 4 pin fans that doesn't fit, you can use a converter cable from 4 to 3, the speed control will not be as precise on a 4 pin fan but should work
Let me make some corrections / clarifications.
All fan signals on a common header are % of full speed whether PWM or DCV. Today's MoBos have plenty of Fan Headers, so PSU control is kinda so "last decade"
DCV controls fan speeds by varying the voltage
PWM comtrols fan speeds w/ a constant voltage but by essentially switching the power to fan on / off
The 3rd pin on both is the feedback control, tells the control system how fast the fan is going with either control method. The 4th pin on PWM is the digital control signal
3 pin - https://allpinouts.org/pinouts/connectors/motherboards/motherboard-cpu-3-pin-fan-connector/
4 pin - http://pinoutguide.com/Motherboard/mb_pwm_fan_pinout.shtml
Both methods have their advantages and disadvantages. PWN historically had better low speed control, tho in recent years DCV has made great strides in this area. PWMs downside has been cost and low speed clicking / hum
Using PWM devices on 3 pin connectors is not recommended.
You want all the fans on any fan hub to be the same speed. Today's MoBo headers can usually do either DCV or PWM with most auto sensing what is attached. NZXT has been emulating many of Phanteks case features, among them the hub. The Phanteks one I am very familiar with... it can take wither a DCV or PWM signal and will power up to 11 3-pin fans giving you a best of both worlds approach ... low cost, no clicking / humming and low speed control. With DCV fans and DCV fan control, you do NOT want to use the provided SATA power cable as the DCV fans will just run at full speed via the 12 power signal. However, you must take note of the amp draw and make sure the total number of fans connected does not exceed the header rating (typically 1 amp) ... with 1200 rpm 140mm fans, you can usually have 6 fans connected.
With PWM signal from MoBo, remember the control is on / off not voltage ... so you CAN to use the SATA power cable for up to 11 fans w/o issue. You wont over draw from the header cause the power cable is supplying power. Now from everything I heard from NZXT Tecg Support, the NZXT fan controller is very much like the Phanteks. I had follow up questions but the didn't respond ... so there are minor differences but not sure of the significance.
But yes, the fan controllers ... at least the oens I have used, are intended to take a PWM signal and control 3-pin fans. Phanteks also does DCV control... dunno about NZXT.
There is never a need to use a 3 pin / 4 -pin converter ... all headers are designed to connect to both so its a waste of money...