Installed set of LL120s; spin up loudly under light short load; how to control them?

[WarMom]

So my case is a Fractal Design Focus G Black. Until today I was using the two stock fans on the front, two 120mms from PC Specialist in the back, and the coolermaster stock fan on the CPU front. I swapped out the 2 front fans and one back fan with Corsair LL120s, put the coolermaster fan on the back of the heatsink and another LL120 in front.

 

I love the way they look but the sound is bothering me - they seem to spin up and get significantly louder for a few seconds at a time under light load before returning. I understand that my CPU - 3900X - kind of has short spikes in load and temp doing small things like loading task manager or icue space, but the old fans never revved up like that with so much noise. Sometimes I'll just be using chrome and it'll sound like gusts howling through trees or waves at the beach, and not in a fun way I'm afraid.

 

All four case fans are connected to one SATA-powered splitter which goes into the Chassis Fan 4-pin on my motherboard (rog x570-F Gaming). Icue says the idling RPM is about 780-800, and the spikes often take it to 900-950 or as high as 1200 before returning back down, along with the sound level. Prolonged gameplay doesn't produce a constant uptick.

 

I am kind of ignorant on how to control fans in general, my only understanding is that it's more or less linked to BIOS and that as far as any control / display apps are concerned I essentially just have two fans - the CPU pair and all four which run off a splitter.

 

Is there any way I can stop them from revving up during a load that only lasts five seconds, or something?

Edited September 26, 2020 by WarMom

[c-attack]

All four case fans are connected to one SATA-powered splitter which goes into the Chassis Fan 4-pin on my motherboard (rog x570-F Gaming).

 

So it appears you are using a powered 4 way fan splitter. While this get the current needed from the SATA line, that connection back to the motherboard header is the speed control and all 4 fan share the same speed -- or at least in theory. What's most likely happening is your 3 different fan types connected to the same signal. That signal from the MB is given as PWM % or if you like, a percentage of the fan's maximum speed. However, it can only talk to the 1 fan and it will use that as the control. The problem is 50% of 2000 will give you a very different speed than 50% of 1000 rpm.

 

Whichever fan is connected to the 4 pin connector will be the controlling fan. All the others should be on 3 pin connectors. LL fans are not particularly loud and don't really deliver a ton of air. However, it seems reasonable you removed the low speed fan that was controlling and put a higher speed on in it's place. Thus now you are getting 75% of a higher speed, or whatever is set in the BIOS.

 

It's tough for me to tell you which fan should be the controller without having fan specifications for them, particularly max speed. However, you can try moving the fan connectors around so a different one is on the 4 pin connector. Really though, you will want to make sure the BIOS fan controls are set to an acceptable level for whichever fan is that position.

 

The second thing is unless two of those fans are on your air cooler, they really don't need to run off CPU temp. That's not a great control variable. However, I will assume choices are limited and in the interest of keeping it simple, see if your BIOS fan control offers "fan delays" or hysteresis that will make the fan wait a period of time (seconds) before changing speed. This will help reduce the speed yo-yo.

[WarMom]

Thank you for the response.

 

Whichever fan is connected to the 4 pin connector will be the controlling fan. All the others should be on 3 pin connectors. LL fans are not particularly loud and don't really deliver a ton of air. However, it seems reasonable you removed the low speed fan that was controlling and put a higher speed on in it's place. [...] you can try moving the fan connectors around so a different one is on the 4 pin connector.

 

So, to clarify something the case fan splitter actually has 5 fan slots because I originally got this PC from a builder and requested a fifth fan which I ended up removing, it was screwing with my pressure balance. They're all bundled up in some netting to keep them together. But, and I can't remember if it has four pins, but one of the connectors of the splitter is marked 'master', so I assume that's the one that'll control it and that's actually the one I've left empty. I'll plug one of the front fans into that tomorrow morning and see if there's any change.

 

The second thing is unless two of those fans are on your air cooler, they really don't need to run off CPU temp. That's not a great control variable. However, I will assume choices are limited and in the interest of keeping it simple, see if your BIOS fan control offers "fan delays" or hysteresis that will make the fan wait a period of time (seconds) before changing speed. This will help reduce the speed yo-yo.

 

Just to clarify something, sorry:

- The fan that came with my Coolermaster, which is now on the back of it, is connected to CPU-Opt.

 

- Only one LL120, on the front of my coolermaster where the stock fan was, is connected to CPU-Fan. Both of these should share the same entry under bios, as far as I understand it.

 

- The other three LL120s, and one PC specialist fan in my top-back vent, are connected on the splitter which runs to Cha[ssis]-fan. They all share the other fan entry in Icue.

 

Tomorrow I'll make absolutely sure that the bundle linked to the splitter goes back to Chassis-fan, and plug one of them into Master. Given the circumstances, I'm starting to wonder if nothing being in master means that effectively nothing is plugged into chassis-fan so CPU controls everything, which would explain upticks. Failing that, I might have to ask somewhere ASUS-specific for help that's based aorund my mobo.

 

Thanks for the responses.

[c-attack]

Yes, the one marked master will be the control and it's % and max speed limit will be the determining factor. If nothing is on master, it likely runs at 100%. That may not matter if they are all 800 rpm fans. If likely does if you have one of the LL120's in there turning at 1700. No need for that.

 

Now that I understand there is CM fan on OPT and LL on CPU, that is essentially doing the same thing as the multi-splitter, but as a pair. On Asus boards, OPT is directly tied to CPU fan with no independent control. It's basically like the fan #2 on a 2 way splitter. So same thing - the % of the LL120 will be the control. The CM fan on OPT will copy the PWM % of CPU_FAN. I don't know what was on CPU fan before, but this one is more straight forward to adjust. LL120 max speed is 1700 (or thereabouts). While fans are not always mathematically linear on their PWM %, just assume it is for programming purposes. If you want it stop at 850 rpm, set 50% as the max. The trickier bit is there is no automatic relationship between Temp X = Fan speed Y. It's mostly about noise levels, as long as you keep some positive speed. In general context, most people will start to first notice a 120mm fan around 1000 rpm. They are clearly noticeable, but pretty effective at 1300 rpm. Most people will consider anything past 1300 rpm loud. You will need to decide what is acceptable.

 

So the good news is you also have fan delay options for your motherboard. However, Asus likes to hide them. If you enter the EZ BIOS, there is a nice area on the main screen called QFan and it shows relatively easy to understand graphs with moveable points. You can use this to set the fan curve. However, the delays are typically hidden elsewhere. Press F7 to go to the Advanced BIOS. Arrow Key -> over to the Monitor tab. Then scroll down. You will see motherboard data. Typically the "Qfan control" sub-menu is way down at the bottom. Hit enter and it will take to the next screen that shows numerical representations of the points you made before. However, also within that for each fan header is a fan delay. For CHA fan headers it will be 0, 12, 25.. seconds. 12 is perfect for most people. That should calm the fans on the 5 way splitter. CPU fan is trickier. The delays are shorter because it assumes you have an actual air cooler connected to CPU and OPT. I am assuming that as well. The delays are in small increments from 2-8 seconds. If these two fans are on your CPU cooler, a few seconds is fine, but 8 might be too much. Also be aware both of those headers have special programming that will override your settings in certain circumstances. If the CPU temp does ramp up rapidly, so will your fans on CPU/OPT whether you like it or not. This is to prevent people from inadvertently jeopardizing their CPU thermals.

[WarMom]

Short version: your advice has more or less solved the issue and now I know how to tweak from here, thanks again!

 

Longer version, in case you're curious: I hadn't noticed at the time, but it turns out my old fans were all 3-pin but also narrow, so effectively only 2 pins of each 3-pin non-controlling connector went in. No wonder they were always running at the one speed. Now one of the (case) LL120s is in the 4-pin, and the LL120s can be controlled. In addition, I used to have 2 fans monitored in Icue at identical speeds, now I have 4 fans - 2 pairs of 2 speeds.

 

Thanks to your advice on QFan and Bios, I've managed to narrow down what the different fan sets (CPU and Chassis) sound like at different speeds, and set my curve as desired. Under advanced, I set the chassis step up and step down to 12 seconds each, and CPU to 3.6 seconds, might turn it dow0n further. Played a game for a while and though I noticed some peaks, nothing egregious and temperatures stayed in the low sixties. I can keep an eye on my temps and sounds and tweak from there.

 

Thanks again!