Optimal Fan Setup for HAF 912

This is my first post on tom's hardware! Anyways, I'm currently building a system using the case HAF 912. It has the following Fan Options
Front: 2x120mm or 200mm
Top:2x120mm or 200mm
Side:120mm or 140mm
Rear: 120mm

Well, currently I have 5 different fans. I have 2x 120mm that came with the system that run at around 1200rpm at max speed, I've bought 2x 120mm fans that run at 2000rpm at max, and I have 1x 140mm at 1000rpm.

The way I want to set up my fans would be like this....

2x120mm at 1200rpm (input) on front.
2x120mm at 2000rpm (output) on top.
1x140mm at 1000rpm (input) on side.

I feel like with this set up, there's a good chance I can achieve either neutral or positive pressure in the system, but I'm still a bit worried. I'm really curious if it would be worth getting one more 120mm fan and having this set up.

1x120mm at 1200 rpm and 1x120mm at 2000rpm (input) on front
1x120mm at 1200 rpm and 1x120mm at 2000rpm (output) on top
1x140mm at 1000rpm (input) on side.
1x120mm at 2000rpm (output) on rear.

So, I'm curious on whether the second build would make a big improvement on the airflow of the system and if not, whether the 5 fans I'm using are in the best position possible!
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  1. Best answer
    Positive pressure isn't beneficial. Ideally you want negative pressure or at least neutral.

    Ideally also, slots would have the maximum size they can hold too.

    In any event, I would do the bottom one out of the two since it is closest to even pressure. I would also tell you to go for the 2000 RPMs both on top and the 1200 RPMs both on the front instead of the way you have it.
  2. Thanks a lot for your feedback,
    I've always heard positive pressure was the best, but could you explain why negative pressure is ideal?
    I'ts too late to get the bigger sized fans, but i'll make note of that next time I make a system.
  3. Best answer selected by infinitelife.
  4. Just a note, this month's MaximumPC had two different articles that both recommend positive pressure.

    Here's a link to a review of many fan configs:

    Not sure what Maximum PC is thinking, but all that I have heard including stuff from this website says the opposite.

    In any event, if their testing says something different and it is well done then I can respect that and if so then it probably doesn't really matter too much either way.

    - Edit - I read the beginning of that article you linked. There it did say (paraphrased), "Getting hot air out is more important than getting cold air in". Getting the hot air out is negative pressure and getting the cold air in is positive pressure. At least on that basis the article seems to somewhat agree with me.

    - Edit 2 - I read a little bit more in the article, and they kind of glossed over something of major importance which is why it makes the positive pressure setups look a whole lot more attractive than they really are. They said that all vents that can be uncovered are uncovered during the testing. This includes the top vents. Hot air rises so plain old holes in the top of the case double as "exhaust fans" in a sense. They don't suck air out, but they do prevent air that is being pushed in from becoming trapped in the PC. Plenty of air escapes through these fan-free holes, though not as much as what comes from a dedicated exhaust fan. That means some setups potentially are benefiting from 2 or 3 exhaust ports that aren't directly mentioned in the article. The existence of these open vents does a lot to mitigate the negative effects of too many intake fans in relation to exhaust fans.
  6. Thanks everyone for your wonderful input. It really means a lot!
  7. Glad to assist.
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