SP120 Pro RGB - Minimum fan speed on Commander Pro

Hi all,

 

So, a quick overview of my system:

 

I've been using a Commander Pro for about a year now to control various fans from other brands, both 3pin and 4pin, with no major issues to speak of. I've now bought a 3 pack of SP120 Pro RGB and I'm having a couple of different issues

 

1. I've tried to use a 3 way splitter to connect the 3 fans to one header on the CP. With 2 fans connected to the splitter, these work as normal, spinning at around 850rpm, but as soon as I connect the third, they all spin up to around 1200rpm. Ive tried 3 different splitters, and they all behave the same way.

 

2. I cannot, no matter what I do, get the fans to spin below 850rpm. I've seen reviews saying that they've tested these fans down to about 350rpm using old-school voltage control fan controllers, but surely I should be able to do this with the CP too? Even if they'd go down to 600rpm I'd be happy, but my intention is to have 6 of them pushing air through 2 radiators, and the PC already sounds like it's going to take off.

 

Does anyone have any suggestions please? Can I use a low noise adapter on the fans to reduce RPM maybe?

Edited May 11, 2020 by M4R7YN
Typos

1) This the problem with three way splitters on the Commander. It's not the fans per se and results vary widely, even with the same splitter from day to day. We usually recommend you don't use them. If you are out of C-Pro fan headers, a powered external hub with a control lead back will help.

 

2) 850 is right around the 60% minimum speed (1400 max) for nearly all DC fans. Not really sure what fan controller is being used to run them down to 300 rpm. Maybe an analog external unit for testing, but your motherboard and any typical controller is not going to be able to run any DC fan at those low levels. The fan has both a minimum start voltage and a minimum run voltage.

 

Not sure on the voltage reducing cable. I have not tested the SP-PRO and do not know how it will react.

1) This the problem with three way splitters on the Commander. It's not the fans per se and results vary widely, even with the same splitter from day to day. We usually recommend you don't use them. If you are out of C-Pro fan headers, a powered external hub with a control lead back will help.

 

2) 850 is right around the 60% minimum speed (1400 max) for nearly all DC fans. Not really sure what fan controller is being used to run them down to 300 rpm. Maybe an analog external unit for testing, but your motherboard and any typical controller is not going to be able to run any DC fan at those low levels. The fan has both a minimum start voltage and a minimum run voltage.

 

Not sure on the voltage reducing cable. I have not tested the SP-PRO and do not know how it will react.

 

Thanks c-attack. What you've said on the splitter makes sense, but I've been using these same splitters with different fans since last June, on the Commander Pro the while time, and I've had no issues. Even now just for testing, I can connect either 3x Noiseblocker E-Loop 3 pin, 3x BeQuiet! Pure Wings 2 3 pin or 3x BeQuiet! Silent Wings 3 PWM and they behave exactly as I'd expect them to. This issue does seem to be specific to the SP120s at the moment.

 

On your 2nd point, I think there probably was an analog controller involved in the testing I'd seen, but of the above fans I'd mentioned, I can get the Noiseblockers to run down to about 300rpm (1200 max) and the Pure Wings to about 500rpm, which matches more with your 60% explanation. I guess this just comes down to motor efficiency variations between fans.

 

I've ordered the low noise adapters anyways, so I'll test them when they arrive and report back, but if I can't get the fan speed lower, I guess I'll just have to turn a couple off when I'm not gaming. Not a huge deal I suppose! I've got for the LL120 on the exhaust fans so these should be fine as they're PWM, just didn't see the epoint using them as intakes when you can't see the light rings!

Ill be interested to know how this turns out. I am a little concerned it will reduce the top end speed without getting you the lower end you want. I don't have hard numbers for minimum run or start voltage on those SP-PRO models. The specs suggest "7v min". Start voltage is probably ~9v. Edited May 11, 2020 by c-attack

I'm not too worried about the top end as I'll never run them that high anyways to be honest. I'm running a custom loop with 2 360mm EK PE radiators (40mm thick) so don't really need to run them at much more than the stock lowest speed if all goes to plan!

 

I've got 3 LNAs due next week I think, so I'll keep testing various config options and report back.

 

PS. You mentioned using powered fan hubs if I was short of fan headers on the CP. I will be, as I'm driving 9 fans. Do you have any recommendations?

Not specifically. I am using a Silverstone one, but that is PWM only. You want something with a circuit board that has direct paths back to the control header vs the "chained" 3-4 way cable splitter that goes end to end.

 

Most any of these should work. If you want it for the SP Pro, make sure it can do DC. Some of them are PWM only.

Ok guys, sorry to drag this back up, but I have a few updates:

 

I logged a support ticket with Corsair and they couldn't understand why I couldn't control the fans properly. They kindly offered to replace the CP, and the new one arrived yesterday. I've fitted it and have exactly the same issue.

 

However, while the CP has been out of the system, I've been running all of the fans in my system from the 3 headers on my motherboard (cheap Gigabyte board with SmartFan5). The board allows me to run the SP120s all the way down to 480rpm, before they eventually stop at 20% power. This works fine with 3 fans on a a splitter.

 

So, in summary:

 

I can control my Corsair fans as expected through my motherboard

I can control other 3 pin fans through the Commander Pro

 

I CANNOT correctly control my Corsair SP120 fans with my Corsair Commander Pro.

 

Surely there is something weird going on here!?

I don't really understand their explanation. The specs on the product page list 7v as the minimum run voltage. That equates to an ~815 rpm minimum if the voltage to RPM curve is linear. Most are.

 

Some controllers are able to play little tricks with the run voltage to start high and keep the fan going below the minimum. My Asus boards were always good at that. I can't explain the electrical engineering aspect of it, but some controllers can get you a bit under the minimum. Others can't. The Commander has never been one to be able to get under specified minimums for any fan I own, Corsair or not.

 

I don't think there is anything wrong with the Commander and you are running into the limits of the fan and controller. If the Commander won't do it, perhaps another will. But then you are getting into a question as to whether this is the fan you want vs auditioning controllers.

In that case, I guess they just replaced the CP in an attempt to keep me happy. I suppose for now I'll just have to run the SPs from my motherboard. The commander works fine with my LLs and pump, plus its still useful for connecting the lighting nodes to and a coolant temp sensor. Hopefully we'll get a reasonably priced PWM replacement for the SP soon!

Just to add, I'm incredibly happy with the SP120 when running from the motherboard. I run them at around 600rpm when gaming, and that keeps my GPU at around 55c and the CPU is even lower, below 50c. They're also barely audible at that level, and disappear completely with a headset on. Just a shame they're not the easiest to control!

The closest thing to what you want from Corsair would be the ML. 4 interior hub LEDs and similar in lighting appearance to the SP-PRO (8 LEDs). It's PWM and will run 375-400 minimum. Good low speed radiator fan. However, if you are content to let the MB run the SP-PRO and don't need to manually control the speed very often, then it may not be worth the cost.

 

*The other downside would be you would need yet another RGB hub for the ML fan type. You can piggy back it on the end of the LL hub, but they won't behave like proper LL fans. Works for solids and basic patterns only.

It looks very much like a limitation of DC control on 3 pin fans.

The mobo may be doing some light PWM on the DC supply to get the voltage down. Sometimes you can hear the fan windings emitting a slight high pitch whine when they run really slow.

The Commander pro probably does strict DC control and if the fans stall, it will ramp up to get them going. Nothing unusual hereif that's what's happening.

 

PWM fans would fit your needs much better. The motor never stalls since it has a constant 12V supply, and depending on what model you get they can run slower than DC fans, AND be more stable at low speeds.

on DC control it's a bit of a lottery. One fan may stop while anothe would run fine when daisy chained at low voltage.

 

And from my experience, the Comander pro can run 3 PWM fans on one header pretty happily. I run two 360 on 2 headers with no complaints.

Yeah I did look at the ML when I was buying the SP but couldn't justify the additional cost. The SP work well and as you say, I don't need to manually adjust them often.

And from my experience, the Comander pro can run 3 PWM fans on one header pretty happily. I run two 360 on 2 headers with no complaints.

 

Yep, definitely works perfectly with PWM fans on a splitter, I've done this with LL120s and with other non-corsair fans, works a treat!

 

Thank you both for your help on this, makes a lot of sense if the CP can't go below 7v. I think I'll just leave the 6 SP120s on the motherboard headers and connect my pump and the 3 LL120s to the Commander Pro.