Phanteks PH-F MP fans resonation

LadFromWales · 5 Jul 2018 at 15:24

Hey all,

I have a pair of PH-F140MP at the front of my Meshify C, and a pair of PH-F120MP at the back, one in the back, one in the roof. All are controlled from one PWM header with an Akasa SATA fan controller cable. There is nothing wrong with the control, but I am finding that when the fans reach 75% or so, they make an annoying resonating/pulsating noise.

Is there anything I can do to prevent this, besides setting the curve so that the fans do not ever reach this speed? Are different fans the answer? What fans would you recommend?

I'm all ears! Happy to change the fans if I have to

EsaT · 5 Jul 2018 at 19:49

Have you tried pressing say top panel by hand to see if that changes sound?

Anyway that's likely some kind interaction between intake and exhaust fans.

LadFromWales · 5 Jul 2018 at 20:58

Cheers for the insight

I've taken the side panel off and employed the highly scientific method of isolating fans by sticking fingers in them.
It appears to be the front two fans making the noise when they are both running together. Between 70 and 80% they make a pulsing noise, below or above that I can't hear it. It is there if I stop one of them, but not as noticeable as when they are both running together. They are mounted a couple mm apart and there is scope to move them apart as the mounting holes for the fan screws are slots.
Kinda annoying as these fans seem to be highly regarded.
They aren't as annoying as the fans on the GPU, but games don't cause those fans to spin up fully like stress tests do, so the case fans are more audible.
For now I've set the max duty to be 60%, bit the board still goes over this if max temp set is reached, which is a good thing I guess!

Are different fans less likely to make these noises? Seems to be once they are at 1200rpm the noise occurs, but of course when past this the noise goes away.

EsaT · 6 Jul 2018 at 10:25

If it happens with side open that excludes interaction between intake and exhaust fans.

Those intake fans clearly have some vibration, with some interference/intermodulation of two of them then causing that pulsating noise.
If you try running fan in hand you would likely notice some vibration of its frame at those speeds.

doyll · 6 Jul 2018 at 12:18

Generally this kind of resonance is caused by something in fan airflow; like grill, mounting frame tab for smaller fan, etc. Can the 140mm front fans be moved in their mounting slots so the 120mm mounting tabs do not intrude into their airflow? Usually spacing the fans a few mm off of mount surface stops the resonance. With slotted mounts I use rubber wire grommets with hole size of mounting screws between fan and case mount instead of in hole.

Obviously this may require longer mounting screws.

What is the RPM range of resonance?

So your case fans are:
2x 140mm front intake
1x 120mm back exhaust
1x 120mm top ???

Have you removed PCIe back slot covers? This greatly improves front to back airflow around GPU thus moving it's heated exhaust air back and out of case.

I suspect the top fan would do more good if used as bottom intake.