Actually, reading further and looking at the specs of my black LL120s, I see this -
Speed 600 - 1500 RPM
So, that may explain why I now have those numbers at the bottom of the range.
How can this be right though ?
I previously had some zero RPMs for one of the fans.
If I want a silent 'Silent' mode, the fans will need to stop spinning. IE. No power pulses to them. Is this actually possible ?