Sharing PWM Case fan with CPU fan in CPU header

[xNadeemx]

Hello, my motherboard only has a 4 pin CPU fan header and a 3 pin chassis fan header, I have a 4 pin PWM case fan and a 4 pin Y splitter, I was wondering if it would be a good idea for the CPU fan and Case fan to share the same CPU fan header through a PWM Y splitter?

Would it be the same as if they both had a respective 4 pin header? (I.E. CPU fan to CPU header, Case fan to Chassis header?)

I'm thinking that it could be annoying if the case fan were to ramp up with the CPU fan, constantly changing randomly... But I like quiet, and I don't see a reason for the fan to be running at full speed using the 3 pin header when idling.

Any concerns or flaws about doing this? What do you guys recommend I do in this situation with a CPU fan, PWM fan, Y Splitter, one 4 pin cpu header, and one 3 pin fan header?

 

[RaDiKaL_]

It's an option indeed, most certainly it will ramp up and down with the CPU, another possibility would be to check in your mobo BIOS if you can regulate the 3pin fan header, this way you could have it in a more silent speed on its own.

 

[Eximo]

Ideally if the motherboard offers control from the chassis fan header that would be the way to go.

If you want the fan to be quieterm but always on, you can run it off of 5V or 7V instead of 12V. (You can get 7V by using 5V as the ground, negative, and 12V as the hot, positive, wire) If you are into re-wiring anyway.

If you have a spare 3-pin to Molex adapter laying around you can try out different configs to see what you like without having to tear into the power supply wiring. Just move the pins on the large end around.

 

[xNadeemx]

It's a Noctua NF-S12A, it comes with a low noise adapter and I'm sure it's not very loud if I were to run it at full speed on the 3 pin header.

I'm sure I'll be happy with the performance and consistent tolerable noise and if for some reason I'm picky, I can use SpeedFan or the Low Noise Adapter that was included to lower any noise, thanks for the replies guys!

*Using 3 pin header*