FSP Twins 500W Redundant ATX Power Supply Review

Fan Speed

When testing in a power supply laboratory it is difficult to take fan noise readings as the noise from the Sunmoon test equipment and air conditioning corrupts everything. The next best thing in our circumstances was reading off the fan speed with a tachometer to get an idea for the noise. The ambient temperature during testing held constant at 22 degrees, with 1 degree of variation. Each power supply had a consistent time period of 5 minutes to stabilise between each load scenario. 

In my experience the following general relationships apply between noise levels and fan speeds, though it can vary greatly between the type of fan used.

• Below 800 RPM – Inaudible/Silent
• 800 to 1000 RPM – Barely audible
• 1000 – 1200 RPM – Audible but still quiet
• 1200 – 1400 RPM – Moderately noisy
• 1400 – 1800 RPM – Noisy
• 1800 RPM or higher – Intolerable

Well, this is just all kinds of strange. The fan did not, I repeat, did NOT run at 12500 RPM. It would have launched into the sky at those speeds. Our laser counter couldn’t get a good reading on the glossy impeller fan design. In my honest, by ear, reading I found the PSU to be pretty quiet up to 60% load. At 80% there was a very noticeable fan noise and turbulence, and at 100% it was very noisy.