Radiator Shrouds

I have a dual 120mm radiator on my watercooling system. The fans are meant to be 'ultra quiet' and i rn them at 6v each (they stop sometimes at 5v).

When on their own i really cant hear them spinning unless i get very close yet when they are sucking air through the radiator they make quite a lot more noise, not loads, but more than id like.

Basically i was wondering; if i built a shroud to offset the fans 40mm or so would reduce this reduce the noise much? Also would the performance change noticeably?

Thanks

Depends what radiator it is, and what fans they are. it also might be yiour fan controller, that causes the fans to behave funny.

A shroud is usually made for better airflow through the rad, it should decrease noise a bit as well..

I dont have a fan controller, i swapped over some of the molex pns and things to make connect them in series. Hence 6v each form the original 12v.

The radiator is the R120-D and the fans are Evercool but in not sure of the details off hand. The thing is, i know the fans themselves are very quiet in open air, so the noise must be air turbulence throiugh the radiator? And i was hoping a shroud would help even out the air flow and reduce the problem slightly.

making the fans pull through the radiator rather then push through makes a bit of a difference to noise i think.

The fans already pull through the radiator, this helps performance more than noise but does help noise too.

Brushless-DC motors dont like running in series that much - and all pc fans are brushless-dc.

Running in parelell with 12v->5v would probably have the same effect (around 6.5v for most psu's).

Most of the airflow on axial fans is on the outer parts of the blades, so having a shroud will help distribute the air better between the radiator fins, which will also decrease air resistance, and so make it a bit quieter - than having all the air going through a few fins.

Axial fans much prefer pushing air, which also prevents flow loss around the radiator.
If your using push-pull you might find it better to ue pull-pull which acomplishes the same thing.

As for shroud, 10-20mm should be enough, more might help but probably wont be much nocicabble over a smaller shrould.

Well at 5v sometimes then stop spinning, why dont they like being in series?

See this thread: http://forums.bit-tech.net/showthread.php?t=87332& from post 9 downwards.

I'd go for the pin swap to get 7v and run in parallel personally. And yes shrouds are good and can help performance and noise. You might also want to use some rubber washers or such to isolate the vibrations of the fans from the radiator / shroud.