XPS 8950, reducing air cooled fan noise

Hello. I’m not asking for help here, I’m just documenting my trials and ultimate solution to reducing my desktop Dell XPS 8950’s awful fan noise when my CPU was at high load. I have the advanced air cooler BTW

I do a lot of rendering so my computer’s fans have to go to quite fast and loud at times, for extended periods. The noise got up to 60dB measured from where I sit, computer under the desk. I found the case fan was the worse culprit, at high RPMs there was a higher pitched noise that was awful. When not under load the computer was almost silent though.

I wanted to avoid BIOS errors, and I wanted the fans to be modulated so that when the computer wasn’t rendering it wasn’t making a lot of noise, so just replacing the Dell fan wasn’t an option. If you do this, the BIOS doesn’t recognise the non-Dell fans and so just runs the replacement fans at full speed all the time. Additionally, I was concerned about how noisy the liquid cooler was at idle too (is it? Can anyone measure it compared to an advanced air cooler?).

I ended up getting an Noctua NA-SYC1 4-pin fan splitter, a Noctua NA-FC1 fan speed controller, and a Corsair ML120 120mm fan. The case fan output cable was split with the NA-SYC1, the Corsair fan installed at the back in the case fan position. The Dell fan was repositioned at the front above the existing intake fan, and connected via the NA-FC1 to reduce the RPMs. The one catch is I couldn’t set the Dell fan RPMs too low or the motherboard wouldn’t regulate the speed properly, i.e. the fan wouldn’t spin down once the processor cooled down/wasn’t being worked. My computer is now quieter at 45dB when under full load, and the pitch of the Corsair fan is lower and easier to ignore.

This worked for me but YMMV, and do this at your own risk, don’t blame me if you fry your computer!

I could’ve also used iCue with its thermometers to replace the Dell fans, but there would’ve still been BIOS errors if I'd removed the Dell fans and I've read quite a few complaints how bloated the iCue software was. I found some little boards with thermometers that seemed to control the fans, but I wasn't sure how to control the fan curves with these solutions.

Or of course I could’ve replaced the case, PSU and motherboard and installed quieter fans or liquid cool it; but this would cost about £500/$670, which I’d prefer to put towards the cost of a new computer.