Question Which of these two options is the better to control fan speeds?

[Big Swifty]

I recently updated to a larger case. Things run cooler without any heat issues during the heat of summer, but the fans spin at 100% all the time which is a bit loud (when the room is quiet) and overkill (esp. with winter coming soon) so I'm trying to find a solution that will give me if not total control of fan speed, then more than I have now.

I have a relatively old, nothing fancy, low power build at the moment. i5-6500, stock cooler, integrated graphics/no dedicated GPU, Gigabyte B150M-DS3H motherboard with only two fan headers - one for the CPU, the other SYS_FAN. The new case is a Lian Li Lancool 205C Mesh with 2x140 intake fans in the front, 1x120 rear exhaust fan, and an included fan controller. Running Windows 10, if that matters.

The case came with the fans already connected and though the ARGB works fine I'm unable to control the case fan speeds through the motherboard using Gigabyte SIV (System Information View) or the BIOS. When I disconnect one of the fans from the fan controller (leaving the ARGB cable plugged into the controller as is) and plug it directly into the SYS_FAN header on the motherboard I am able to control the fan speed through Gigabyte SIV. The below image shows what I've described above (my notes in red).

The replacement controller mailed out by Lian Li is stuck in Customs where it's not worth the time or expense to get it out so I'm hoping that using a PWM fan splitter cable(s) with as many 4 pin connections as needed will be the most practical solution. I understand that I won't be able to control each fan individually

First option is connecting all three case fans > SYS_FAN header using a single splitter cable and being limited to having them all run at the same speed. Second option would be to connect the two 140 intake fans by splitter cable > SYS_FAN header and using a second splitter cable to connect the CPU fan and rear exhaust 120 fan > CPU fan header so that I can have separate control for the two intakes and the CPU/rear exhaust fans.

Assuming either option would work (?), which of the two would be better? I'm leaning toward the second option as it would be less amp draw on each fan header while giving me more control, but I'm not fully aware of the advantages/disadvantages of each option. If the second option is better are there any suggestions or advice as to how to set up the fan curves so that I can maintain slightly positive pressure as long as the temps stay good? As it is now, the interior is a bit dustier than my old mesh front case. Not sure if that's because of the design, because I now have 2x140 intakes instead of 2x120 with the same 1x120 exhaust, because it's a slightly larger case, or some other reason unrelated to pressure.

 

[Paperdoc]

I suspect the problem MAY be that your mobo's SYS_FAN header operates ONLY in the older Voltage Control Mode even though it has 4 pins. The fan HUB supplied with the case can control the speed ONLY of 4-pin fans (which I believe you have) and ONLY if the host header it is connected to uses the new 4-pin PWM Mode of control. Your mobo's manual does not specify this directly, but the labels on the SYS_FAN header indicate it may NOT be able to use PWM Mode and supply the required signal to the Hub. In such a case, the fans will only operate at full speed always.

Now the design of 4-pin PWM type fans includes a backwards compatibility feature. Although the ideal way to control their speed is to use the PWM Mode as it is designed, IF you connect such a fan to a header using the older Voltage Control Mode that fan's speed WILL be controlled. Probably you have seen this already when you moved one fan's connector to the SYS_FAN header. So your best solution IS to use a SPLITTER to connect to the only SYS_FAN header all three case fans - fan motor cables only, NOT the ARGB cables. You need a Splitter with at least three output "arms", simlar to this ( a 2-pack)

https://www.amazon.com/ThreeBulls-Splitter-Computer-Extension-Converter/dp/B07MXNT6V4/ref=sr_1_9?crid=32W82XSSBD8Z&dib=eyJ2IjoiMSJ9.IjBh05gyy4VBJ_BZr-mv9EPhV_jkxF3034ZEpTS7hL6GMFsItQfi89yxAyBBwxqdY1OBlsmHdvYHvYqTb122jE6vnqa-MVZeF9oWBn7NUqg_K4FZmseCbKKRsRVU-t8CWUV_2oNUahZIXjOPit6LP3Gdo3g3Ygx9NSFQgtHLn-pYpOFrEVhpo9J_mciyo1tuprUcvUb9bQBxotUxJ7Pq0YtAx6irmDXyIeJZwphSG28.Rjaph60C12XDiiVIJ8OS1WBxf4NaJOzSX__ErzAjS04&dib_tag=se&keywords=fan+splitter+4+pin&qid=1710607745&sprefix=fan+splitter,aps,94&sr=8-9

NOTE that sellers wrongly use the labels "Splitter" and "Hub" as if they are the same, and they are NOT. The SPLITTER I lnked above has one input that goes to the mobo header, and 3 outputs for fans. It has NO other connectioons. A HUB is different because it has a third connection that goes to a SATA power output from the PSU, just like that board in your case. You cannot use a HUB for this.

FYI, another form of Splitter may look like a circuit board like this with five output ports

https://www.amazon.com/ThreeBulls-Cooling-Splitter-Adapter-Computer/dp/B07M5P7VHG/ref=sr_1_8?crid=32W82XSSBD8Z&dib=eyJ2IjoiMSJ9.IjBh05gyy4VBJ_BZr-mv9EPhV_jkxF3034ZEpTS7hL6GMFsItQfi89yxAyBBwxqdY1OBlsmHdvYHvYqTb122jE6vnqa-MVZeF9oWBn7NUqg_K4FZmseCbKKRsRVU-t8CWUV_2oNUahZIXjOPit6LP3Gdo3g3Ygx9NSFQgtHLn-pYpOFrEVhpo9J_mciyo1tuprUcvUb9bQBxotUxJ7Pq0YtAx6irmDXyIeJZwphSG28.Rjaph60C12XDiiVIJ8OS1WBxf4NaJOzSX__ErzAjS04&dib_tag=se&keywords=fan+splitter+4+pin&qid=1710608035&sprefix=fan+splitter,aps,94&sr=8-8

Either way, a Splitter (or a Hub) will send back to the host header the speed signal of only ONE of the fans attached and ignore all the others. In the "group of arms" type, note that ony ONE of the outputs has all 4 pins in it, and the others are missing Pin #3. Only the fan plugged into the 4-pin output will send its speed signal back to the mobo header. For the circuit board unit, the only port that sends back a fan speed is the one marked for CPU. Do NOT use this for your CPO. Just plug ONE of your case fans into that port.

I recommend connecting all three of your case fans to the only SYS_FAN port this way. Virtually all such headers can supply up tp 1.0 A max current to the load conneced, and most fans draw less than 0.25 A each, so connecting three of these to one header is quite all right. Splitting them up as you suggested would NOT give you separate controls, because whatever you connect to the CPU_FAN header always will be doing whatever that header does. And you NEVER want to make the cooling of your CPU depend on what you wish for a case vventilation fan. So in your Second Option the rear case fan would only be able to do whatever your CPU cooling fan does.

Power and control of the ARGB lights on your fans is completely separate from their motors. That is why each fan has two different cables. So you should leave the lighting cables attached to that Hub board supplied with your case and let that control the lights. Since your mobo does not have an ARGB header, I assume you control the lights using buttons on the case.

 

[Big Swifty]

Thanks for the response. Insightful, though I'm not sure I understood everything exactly (I'm nowhere near fluent in tech) I think I got the gist.

I wouldn't have been able to say why, exactly, but I had a feeling that the old motherboard was somehow the limiting factor due to something like the Voltage Control Mode you described and not being able to run in PWM Mode. On my list of things to update in the next year or two is the CPU/motherboard, but I'm looking for a solution with the build I have now.

So just to confirm, using a splitter cable similar to the one in your first link and where I connect all three case fans to the same SYS_FAN header will allow me to control the speed of all three case fans using a temperature based fan curve - the main limitation being that all three will run at the same speed. As you pointed out, the amperage draw of the three fans on one header shouldn't be an issue. I completely understand the ARGB separate cable aspect. The CPU fan stays as is, being the only fan connected to the CPU FAN header.

I'm assuming it won't matter which of the three case fans I connect to the 4 pin outlet. The other two fans connected to the 3 pin outlets will be told to run at the same speed (or voltage) as the fan connected to the 4 pin outlet. Speed will just be controlled by Voltage Control Mode as opposed to PWM Mode.

 

[Paperdoc]

You got that all right.

Just some tech details to help you understand the workings and terms - you do NOT need this to do what you want.

The older fan style uses three wires and a female connector on the end with three holes. The speed of the fan is controlled by varying the VOLTAGE supplied to it on Pin #2 of the header. (Pin #1 is Ground.) That Voltage can range from 12 VDC for full speed to 5 VDC to run minimum speed without stalling. Pin #3 carries a pulse train signal generated by the fan back to the mobo header where it is counted to calculate its speed. However, the header does NOT use that info for its work to vary the speed so it can control the temperature at a sensor. It really does not care what that speed is. It DOES monitor it, though, in case there is NO pulse speed signal to indicate FAILURE of the fan. That would generate an on-screen warning to you. Such fans commonly are called 3-pin fans or Voltage Control Mode fans.

The newer fans use a fourth pin in the connections system. It carries to the fan the new PWM signal. In this system the Voltage on Pin #2 is always the full 12 VDC. Inside this fan type there is a small chip that uses the PWM signal to modify the flow of current from that fixed 12 VDC power supply line through the motor windings to reduce its speed to what is desired. This is called a 4-pin fan, or a PWM Mode fan, because that is how the speed is altered. The backwards compatibility of this design I mentioned comes about this way. IF such a fan is connected to an older 3-pin header (OR to a 4-pin header that actually is sending out the Voltage Control Mode signals of a 3-pin header), it gets NO PWM signal from Pin #4 so the chip cannot alter the current flow. BUT the VOLTAGE supplied to it is NOT the fixed 12 VDC - it is a VARYING Voltage, so its speed IS controlled in the same manner as for a 3-pin fan.

In your case, the fan HUB board included in your case works this way. It is intended for use ONLY with 4-pin PWM style fans. So it gets POWER for all its fans directly from the PSU and sends all of them a fixed 12 VDC supply on Pin #2 of each output port. It draws NO power for the fans from the host header, so the limit on header max current does not apply. It does get the PWM signal from Pin #4 of the host header and sends that out to all its fans, but this does not draw any significant current on that line so there is no limit on how many fans can be controlled this way. So you can see that IF the host header does NOT operate in the new PWM Mode and send out any PWM signal, the HUB can send no such signal to its fans. Then they all are working on an un-modified fixed 12 VDC power supply, and they run at full speed always.