Noctua NF-A14 PWM Minimum RPM

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Hey folks, first post here, so please go easy on me...

I'm running a couple of NF-A14 PWM case fans, in a Fractal Design case, with a ASUS Maximus Hero MB, and I don't seem to be able to get the fans to spin slower than 650-700rpm. I'm using AI Suite 3, and the Fan Xpert software to tune the fans, and it seems to indicate that ~650 is the min rpm...although the manufacturer claims they will go down to 300rpm +-20% with PWM.

I understand that there are options in the BIOS to control fan speeds, and I went in and set them to be 300rpm min speed. No change.

I also have two NF12's running on a H100i cooler, and they seem happy to 'idle' at just over 200rpm.

While the noise of the 14's running at 650rpm isn't bad, I'm trying to get the overall system noise as low as possible as I'm in a very quiet room and the machine isn't doing heavy lifting 80% of the time.

How can I get the minimum rpm lower on the 14's?

 

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Make sure your 4-pin header actually uses PWM signal. Some 4-pin fan headers, especially non-CPU fan headers, regulate fan speed by changing voltage instead of sending PWM signals. I'm guessing the header you have the fan connected regulate fan speed by changing voltage and the minimum voltage it can send is higher than the fan needs to run at the minimum RPM. Your motherboard manual should tell you which fan headers actually sends out PWM signal.

You can always use a PWM splitter and run your fans off of your CPU fan header (make sure to get the one with separate cable for power vai molex or SATA power cable as not to kill the CPU fan header).

FWIW, I can get A14s to run at minimum RPM on ASRock Z97 Extreme4 using either its CPU_fan 1 header or Chassis_1 header.