Fan bearing types

[Sojiro1]

What's the different between fluid dynamic bearing and double ball bearing?
Thanks

 

[basroil]

Unless you're designing a turbine, don't worry about the difference. Instead just look at reviews about how long the fans last and how efficient they are (noise vs CFM). Here's a great source of info on the subject: http://www.silentpcreview.com/section12.html

 

[clintonfisher102490]

FDB will be quiter and last longer. The longer a fan runs the louder they typically get as they warm up. Its not always noticeable but it does happen.

It really just depends on the quality tho. A cheap FDB fan will be louder and will not last as long as a high quality DBB fan.

Just depends on the quality. The fan on my $150 Seasonic is FDB it's 2 years old and still silent. Granted I bought one more powerful than I need for future upgrades and to keep it quiet but I've never heard the fan. I'm sure if I turned the computer around and our my ear at the vent I could hear it but typically the power supply are one of the loudest components.

To summarize FDB if higher quality than DDB fans but a generic FDB fan can be worse than a high quality DDB fan.

 

[basroil]

clintonfisher102490, for most case fans the bearing does nothing for noise, rather the fan blades themselves, interaction with the supporting frame, and motor (and other electrical components) are an order of magnitude larger than any bearing issues. Likewise, the noise to CFM and noise to RPM are almost entirely dominated by everything but the bearings. If you're confused, follow the link and check the spectral graphs yourself, it's quite clear that bearings never show up except in very rare (possibly defective) cases (they would show up as a peak at some, perhaps fractional, multiple of the fan RPM)

To summarize, fan bearings aren't really something to worry about unless you are making them (in which case you should contact a professional instead). Check the quality at silentpcreview and chose on results, not theory. After all, who would ever buy a crappy PSU with good specs like the EVGA GQ line?