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A fan on a fan??

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Oct 2, 2002
University of Bath, UK (but im Dutch!)
is it possible to put a fan on another? will it screw up the airflow?
I mean a 80mm silent fan with a 80mm screamer on top and have the silent fan running all the time and have a switch in the fanbus to turn on the screamer when i'm folding @100% or playing games etc.

How quiet are volt modded deltas also, could do that, but im looking for SILENT (<25Db) when i run it at night with the loud fan off.


Willem :D


May 8, 2002
Yeah, the airflow will be screwed up. When the screamer in your system is off, the silent fan wil be having a hard time to suck the air through the screamer. When you start the screamer it will be having a hard time to force the faster air through the slower fan. In the end the silent fans drive unit could be destroyed due to the magnets swinging by inductors too fast acting like generators, though it's a far fetched idea.


Sep 3, 2002
My Sunon 80mm 84cfm w/ 7v mod is relatively quiet. By that I mean that it's not very noticable over the case fans and still moves a good deal of air


Sep 10, 2002
Pittsburgh, PA
NOt only is it bad, but it will cause your quiet fan to run louder, as the rushing air around the off 'screamer' will have to move the same amount of air through a smaller space, causing it to whine and louder 'air rush'. The same holds true when you turn the screamer on.. you are effectivly restricting the exiting airflow with the slower fan.

The only true way to get 2 fans to work in tandum is to have the fans have the same:

1: pitch on the blades
2: same # of blades
3: exact same RPM (basicly impossable without complicated timing circuits)

Even then... Its still iffy.. General rule... don't do it.. It usually does more harm than good.

Best bet is to put the fan on a rheobus and turn it down at night..


Jun 8, 2002
Dunstable, uk
actually, it seemed to have a slight improvement in my case.

yes, thats right i tried. and yes they were louder....untill i put them on my h/s - then they were actually slightly quieter than one fan, while droping 1-2c.

oh and btw they wernt two identical fans