Fans ontop of eachother?

1 Pull, 1 Push. Don't stack, it doesn't help at all.

Only adds more turbulence noise and unwanted vibrations.

Oh. ok then.

means its no use stacking the fans?
thats a cool thing I came to know

don't stack. you'll just make the fan next to the extra fan spin faster than its intended speed due to less resistance, and end up getting more noise, more heat (hot motor and bearings) and a prematurely worn-out fan.

I've seen a few posts of people ripping the fan out of the housing and using that additional housing as a sort of mini tunnel after the fan... what's the go with that?
Are there gains to be had with riggin up a wind tunnel effect before the air reaches the heatsink?

I've seen a few posts of people ripping the fan out of it's housing and using that additional housing as a sort of mini tunnel after another fan... what's the go with that?
Are there gains to be had with riggin up a wind tunnel effect before the air reaches the heatsink?

The term for those "mini tunnels" is shroud. It helps get rid of the dead spot caused by the hub of the fan. Usually decreases temps and can decrease noise also.

shrouds help alot i use them

Oh fair enough. I don't have any spare fans lying around willing to 'donate' themselves to the cause... So what do you think of poor mans rendition of using some thin cardboard (like manilla folder stuff) and sleeving into the fan's original shroud, where there is that little gab between it and the fan blades?
Bit of sticky tape, maybe a dash of spray paint...
Also is it more beneficial to have an additional shroud on the intake, exhaust or both sides of the fan?

I suggest going to a local store and asking for old fans. Where I live one has a full box of crappy old 120mm that are like 2$ a piece.
I actually did my first shroud with a Kaze 3000 that died due to a terrible accident.