Worth changing/adding case fans

[Mehta23]

I have a CM Strom enforcer with the standard led 200mm at the front and a noisy 120mm at the back.

I was thinking of getting something like a Corsair AF to replace the back one and maybe another at the top? However I don't the how much of a difference in quietness and extra cooling it will make.

I also heard that adding fans can disrupt airflow?

Also, if i were to get an aftermarket cooler (like the cm hyper 212) would I need to change the fan on that too?

[Spank]

I changed the fans in my 650D for 2 140mm & 1 120mm AF (& a CM 200mm front fan) & they are quieter at 100% than the standard fans were at 50%

[Pob255]

I've got the HAF 912+ which is basically the same case (the front bezel and side panel are the only difference)

The rear stock 120mm fan shouldn't be that bad, if anything the front 200mm is louder at full speed.
Check that you've not got a wire getting sucked into it, a wire getting clipped by fan blades make a heck of a racket. (saying that are you 100% sure it's not the cooler fan? don't know your full specs but it fairly easy on the intel stock cooler for the fan blade end to to clipping on it's own fan cable)
But it could be just a bad fan.

I've currently got a BitFenix Spectre 200mm fan in the top http://www.specialtech.co.uk/spshop/...pid-13147.html and a 120mm 9 bladed fan (arctic cooling I think) on the side (with a fan filter)
The BitFenix doesn't move as much air as the Coolermaster 200mm megaflow (fan on the front) but it's slower, narrower (20mm vs 30mm) so it doesn't take up as much space and is quieter.
I've got all my fans hooked up via my motherboard which can actually control the speed of all the fan headers (many lower end boards only control cpu and 1 of the system fan headers) the front 200mm and two 120mm fans run at around 600-700rpm and the top bitfenix 200mm at around 300-400rpm.
CPU cooler is the Hyper 212+ with two Akasa Apache 120mm fans in push pull both off the cpu PWM header via a splitter cable (due to them being different revisions on fan runs at around 800rpm idle and the other around 600rpm idle)
Loudest thing at idle is my hard drives.

The original hyper 212+ fan wasn't great, sort of, it's not a bad fan just way too fast and loud at full speed, PWM control works by a % of the full speed and with a full speed of 2000rpm it was hard to get it to go below 1200rpm, the hyper 212+ has been replaced by the hyper 212 EVO which is overall better, better heat pipe flattening (reducing the voids between the pipes and increasing contact area), better fan clip mounting (replacing the fiddly wire clips with a simple plastic frame) and a better fan (full speed is now 1600rpm so easier to get it to go down to a slower speed)
Other to look at are the hyper 412s (fewer fins so less air restriction at the cost of less cooling area) the Zalman CNPS10X Optima, Corsair A50 (although the fan isn't great on that one) Enermax ETS-T40-TB, Thermalright True Spirit 120, Gelid Tranquillo v2
All are around the £20-30 mark are are good for non-overclocked to light overclocked and very quiet performance

Disrupting air flow, depends on the case, the fans and the overall setup.
generally speaking, you want the air to come in at the bottom front and out at the rear and top rear.
you want to generally avoid putting fans in conflict.
If you've got a heat pipe tower cooler in it's classic setup, ie the fan in front of it pushing air from in front of it back to just in front of the rear case fan then you don't want tot put a high air flow fan in front above it, as that will be pulling out the same air the cpu fan is trying to suck in, above the heat sink but behind it is ok as you're sucking the hot air out and not conflicting with the cooler air flow.
(A weaker fan is less of an issue)
a top rear fan and rear fan are not always optimal but while they might be conflicting slightly, as they both try to pull air from the same place, they will still move more air than just one fan.
Most 120mm fans at 1200rpm of less just don't have the air flow to cause any major conflict with each other.
Avoid putting an intake and exhaust next to each other (ie don't have a top rear fan pulling air in and an rear fan exhausting as they will be cycling air around and not pulling it through the case.
You want to be pulling cool air in, travelling over hot components before exiting.

EDIT; I'd really recommend the BitFenix 200mm for the top if you're sticking with air cooling, but I did originally get mine back when they where cheaper and more readily available, I got it when it was only £8 and the coolermaster mega flow was still £16

[dacads]

Ideally you want a positive air pressure which means more airflow from intake than exhaust. So make sure the intake fans have a total CFM that is higher than the exhaust fans. Also stick some dust filters on the intakes as these will stop the dust getting in

[Mehta23]

The front intake has a dust filter, and theres also one underneath the PSU.

If I were to add extra fans on the top, I'd probably use them as outtakes.

So should I bother with changing the fan at the back? The noise is intermittent, sometimes it's pretty silent.

[dacads]

I don't see why you should tbh, unless you want a change of colour

[Mehta23]

Just because of the noise really, and if a replacement is better, although like I said, my temps are pretty decent.