PWM uses bursts of electricity to run your fan in an attempt to save electricity. DC is simply running constantly at a set speed with the electricity always on.
PWM uses bursts of electricity to run your fan in an attempt to save electricity. DC is simply running constantly at a set speed with the electricity always on.
The main difference is PWM allows operating fans at a much lower RPM than voltage control does. That's because the "bursts" are always full 12 V which can kick the fan to start rotating. The duration of the "kick" just gets shorter (percent of time) in duration to lower the RPM.
DC control just lowers the voltage which doesn't kick it into starting when it gets below about 5V or so. That can damage the fan if left not rotating with 4 or 5 V on it for extended periods so many fan controllers won't give it less than 6 or 7 Volts minimum.
It's less a big deal these days with the ultra-quiet fans made by BeQuiet, Noctua, Arctic and others as the operating RPM at even 9 or 10 volts is whisper quiet.
All systems are different...different fans and cases with different fan locations and as well different ambient temperatures in your room. You have to experiment a little with it, or just pick a speed that's quiet but on the edge of being annoying. If it's still too hot then you may need to go looking for different fans, or examine your fan layout in the case.