thanks for the info. I mistakenly wrote CPU when I meant PSU. I believe the PSU fan is the fan that is the loudest. I was reading this thread
on someone who swapped out his PSU fan, but the PSU will boot loop if you swap a fan out. So looks like this will not be possible.
I'm running 12 2TB drives in this thing. Do you think replacing the 6 fans with the SuperMicro fans you mentioned above would be enough airflow? Your system having only 2.5" drives is quite a big difference in temps.
It might, but I've got no idea for sure. Not enough if you're going to pull a lot of watts for any length of time. But, if you're going to have typical home lab utilization...long periods at idle... it may be OK. I'm not familiar with Chia though, so YMMV.
One way to quiet things down is to put fans on the biggest heat producing motherboard components (CPU and SAS chip) . That way, the chassis fans aren't having to cool the CPU and SAS chip, they only have to pull some air past the hard drives and push the warm air out of the chassis. Hard drives don't need a lot of air flow, and the air doesn't have to move as fast if there's separate fans on the CPU & SAS heatsinks. On mine, I used a Silverstone active cooler (SST-NT07) on the CPU and a 40x10mm fan on the SAS chip's heatsink. The Silverstone has threaded screws (not push pins) so its a match for the threads on the motherboard's backplate. For the 40mm fan, I think I used some 3mm machine screws that were a friction fit between the heatsink fins.
I also had an open frame passively cooled PSU left over from an Asus ITX case that was damaged, so I replaced the PSU as well. The "new" one uses a power brick, so a lot of the PSU heat stays outside the case. But, my setup didn't draw much power even with the CPU at 100%, and I already had the PSU, CPU cooler, and Supermicro fans in my spare parts box. I'm not sure I'd have put much money into it if I'd had to buy everything. The motherboard in these is probably almost 10 years old after all.