In keeping with my long-standing tradition of thinking I know what I'm doing when I don't, I recently ordered two single Corsair LL120 RGB fans without realising that these are intended as expansion modules for those who have already splashed out on the triple pack with the hub and lighting node included. All I wanted was 2 fans with white housings and white LED lighting for my AIO radiator to bring a little more contrast to the "black and white" build I'm working on. In retrospect the ML140 PRO LED White fans would have been both better and cheaper. But I am as inpatient as I am overconfident, so I decided to apply myself and see if there was some way to rescue the situation.
And there was!
I'm posting this to let anyone in a similar situation know that you can control at least 2 (and maybe more) Corsair RGB fans without the hub or the node if you are prepared to do a little soldering, as long as your motherboard has an addressable RGB header. The only thing you won't be able to do is control the fans individually.
And here is how:
1. Establish which of the pins on your motherboard's addressable RGB header are the 5V, the Data Out and the Ground pin. On the ASRock B450M Pro4 it's (from left to right) 5V - Data Out - Blank - Ground.
Note: Make sure you are using the addressable RGB header, not one of the normal RGB LED headers as these are 12V and will fry your fan LEDs. On the ASRock B450M Pro4 the addressable header is grey while the other 2 are white.
2. If you have an RGB header cable already, strip the wires on one end and set it aside. If not, you will need to source one or find a suitable alternative. I tried using a USB 2.0 cable, but the RGB header pins appear to be thinner than USB header pins, so this didn't work. In the end, I used a 5-pin subwoofer speaker level input cable from my car audio junk box and cut it down to four with a Stanley knife. This turned out to be ideal because the pin spacing on a speaker level input cable is just right, they grab the RGB header pins well and the other end of the cables are already stripped.
3. The 4-pin LED cable from the Corsair LL120 fan (and I assume the other models, but don't take that for granted) labelled "TO RGB HUB" is composed of, in order, 5V - Data Out - Data In - Ground. I initially made the mistake of assuming that the end cable with all the grey markings on it was the 5V, but it turned out to be the other way around. To confirm you've got it right, pull the connectors out of the plug, stick one of the outside connectors into the 5V hole on a female Molex plug (far left if the two indentations are at the top) and try out the other three connectors on one of the ground holes (the two in the middle). If you get lights on the fan (mine turned red), you've found your 5V side.
4. Match up your 5V cables and solder. Match up Data Out from header to Data In on fan cable and solder. Match up ground cables and solder away. Insulate your soldering points and wrap it all up in heat shrink or electrical tape and, presto, you're done!
Wired up in this way, my two fans work perfectly with ASRock's Polychrome Sync software. If you are using Polychrome, just set the "Addressable LED Number" to however many LEDs are on the fan. It's 16 for the LL120.
I know using the Corsair hub and node provides a little more functionality, but for my purposes this solution is ideal as I will not be adding any additional RGB fans or other peripherals. That said, my motherboard still has two normal RGB headers available in case I ever get strip fever.
I apologise to those of you who are smarter than I am for teaching you to suck eggs, but I spent hours scouring the web for a solution and ended up having to piece this one together from a number of sources, so maybe someone out there will find it helpful. I, for one, was never going to spent £85.99 on the three-fan pack with the included controllers, and it's nice to know that I didn't have to. In fact, having proven to myself that my motherboard and ASRock's RGB controller software are perfectly capable of managing these two fans (and possible more) without the need for any additional hardware, I would take issue with Corsair for not making it easier to do so. At the end of the day, the cable I put together could be produced at negligible cost and included in the single fan packs as I believe most addressable RBG motherboard headers use the same pin configuration, but please call me out on this if I'm wrong.
If the above guide is too confusing, I would happily produce some visual aides. Just let me know.