[pHaestus]

No experience with the NMBs but I have used 12V and 24V Comair Rotron Patriot fans before. jafb2000 is right about them; they don't respond as well to voltage reduction as you'd expect. The 24V running at 12V is ok but there is a definite bearing noise coming from the motor. Not annoying but present. 12V at 6V same thing. I had no luck running the 24V fan at 7V btw.

And he was referring to the noise that fans make while in PWM. If you haven't run fans with PWM controllers then YOU don't know what YOU'RE talking about until YOU actually do so. Ball bearing fans can quite often develop some extremely annoying and industrial sounding noises when you adjust their power with PWM. I haven't put the Patriot on PWM yet (though that's a fine idea) but I wouldn't doubt that it does this when I think about how other beefy fans (Vantec Tornados, Delta EHEs, etc etc) react.

People have had some success taking fine grain sandpaper and sanding the blades of the rotrons smooth. I have heard that this will reduce noise considerably. People sometimes also have to oil the bearings of the Rotrons which came from surplus stores...