Back to fans. Noctura not-f12 is supposed to be a quiet 120mm with speeds up to 3000rpm. From reading all this, noise is the issue but you have to decide if you want speed or noise. The faster the s5 hashes the louder the fan because in order to keep the s5 in working temps (below 60) you have to push a lot of air and have the s5 is an ideal location. If you want a quiet fan then you need to sacrifice hash speed because the air displacement from fan has to exceed the heat generated to keep the s5 cool. This has been my struggle.
But I can't figure out why the s5 needs to be below 60c? Most computers run at or over 60c. The over temp cutoff is software set at 80c. I do get some hw but over a 12 hr period and from what Ive read some hw is ok but when does it become an issue?
Unlike the Spondoolies or Hashfast chips (or your CPU) the S5s don't have a thermal diode right on the chip. The temperature sensor is on the back side of the board, and so is really measuring the temperature of the PCB. It's unknown (at least to me) what a good rule of thumb is for mapping die temperature to the temp sensor reading, but it's pretty much guaranteed to be a decent bit higher than what the unit says.