Hi - Just to throw in my 2 Euro cents here:
All I've read in this thread is RPM, decibel and CFM... but you're totally missing one important number:
Static pressure (Measured in 'mm/H2O' or sometimes in 'Pa')
Especially systems been cooled by sucking air through the whole box having obstacles (i.e. power-supply, big objects like humongous caps etc.) in the way of the draft it's all about how much '
ooomp' poor little fan can deliver.
It's a bit like horsepower vs. torque.
Nocturas and the likes are the Ferraris in the world of fans - lots of HP (CFM) but comparably low on newton meters (mm/H2O).
And then there are the tractors. Not the fastest and nicest ones... but boy do they pull.
My '30 has a Panaflo FBK06-12L - can't find a datasheet for it, but its 40mm brother has a static pressure of 2.5 mm/H20 - I dare betting the 60mm Panaflo is at least pulling 3 mm/H2O.
The recommended Noctura is at 2.18 mm/H2O
The recommended Delta Electronics AFB0612EH-ABF00 is at a absurdly poor 0.544 (@38.4 CFM) 8-o
So if there's not enough draft, after some hours your PSU might get cooled ok'ish, the flyback's already sweating and the the harddrive is about to be grilled by that Turbo040 down there... :sadmac:
So in a one sentence: "
Don't look at CFM. It's mm/H2O that matters!" (At least in the case of compact Macs... pun intended ;-) )
I've written
a bit more detail in this post over here.