CM NV 690 - Extra Fans - Positive Air Pressure Questions


Ready to purchase a CM NV 690 and I have a few questions, if I may?

I will be purchasing 2 extra fans, Skythe S-Flex 120mm (1900 RPM), one for the bottom and another one for the top of the case and I will also be adding a Skythe Fan Controller KM02.

The bottom fan will be an intake.

I will most likely add a third fan, 80mm Skythe fan, on the right side of the panel also as an intake but will have a limited role.

In order to create a positive air pressure in the case, hence less dust, means having more fans blowing in than out so that the case has a net positive air pressure.

My questions are as follows:

1) Should the top fan also draw air in?

2) Are two additional fans enough to create such pressure?

3)) Are there any exterior filters that can be attach to the top fan and/or side

4) And: Is there any major differences between the CM NV 690 vs the ordinary CM 690 beside the window (that I want) and one less fan and the color?

The Cm 690 with the extra purchase of the window actually cost less money with the free shipping than the 690 NV 690?

Thank you,

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  1. pinibo said:
    In order to create a positive air pressure in the case, hence less dust, means having more fans blowing in than out so that the case has a net positive air pressure.
    Positive air pressure alone will not promote less dust entering the case. You'll have to have good intake filters too.
    Adding more intake fans will introduce more dust into the case unless you have a very good filtering system. Bottom fan will be worst offender.

    (1) Since warm air naturally rises top fans should be set to help exhaust rising warm air, not fight against it's natural tendency to rise.
    (2) Positive pressure is less important than "air exchange" - moving cool air in and warm air out.
    CM 690 has about 1.5 cubic feet internal volume. If you're intake fans deliver 90 CFM of air though the case you're doing an "air exchange" about every second. That should be enough to keep any desktop system cool enough.

    Why not test the system temps with the stock fans first. Then test after adding a top fan. Keep testing till you know how your fans are affecting the overall system temps. Try different fan configurations and measure those temps.

    To be honest I'd trust the case design engineers that the stock fans are "good enough" for a even a "hot gaming system".
  2. 140mm is better

    IMO, the one with out the window is better because you could get it a lot cheaper and has 1 additional fan spot where the window is, buts it your choice. there is not much different between the two other than that. (the front LED fan is really weak, you might want to switch that, but since you are adding more fans in anyways, i dont think you have to.)
  3. 1) Absolutely not

    2) Probably

    3) Kinda, I dont belive they are external, and you wouldnt want any filters on your exhaust fans.
  4. The classic configuration is cool air into the bottom/front of the case and hot air out of the top/rear of the case. An additional fan on the side panel can be used to direct cool air toward the video card or cpu depending on location.

    One way or another, directly or indirectly, dust is always going to be a problem.

    There is an additional problem. Dust filters, perforated mesh, and fan guards severely restrict ventilation, airflow, and cooling.
  5. I have a CM690. In it there is a filter for the front and bottom. The sides are the only ones that needed filters, (I used black knee highs trimmed to fit). While I was still shopping I thought I saw a filter on the windowed panel. Front bottom and side should be intake, top and rear should be output, no filters should be needed for the output if the input filters are doing their job.
  6. Thanks for your replies.

    The choices should be as follows:

    1) CM NV 690 or CM 690 + window, depending on the price.

    2) Three additional Skythe fans: one 120mm for bottom as intake, another 120mm for top as exhaust and one 80mm on other side as intake.

    3) Skythe Bay Fan Controller.

  7. Walked in at CompUSA in Altamonte Springs in Florida this morning.

    There it was...a CM NV 690 for sale at 109.96. Because it was over $100 +, I got an instant $10 rebate. Total with tax after rebate: $106.96...and no shipping fees!

    It is now sitting at home waiting for the rest of the parts to come in. :)
  8. I agree completely with WR2, no matter how carefully you plan, it's still possible to get "dead air" spaces where you don't want them to be i.e. at HSF and around the GPU. After installation, always check temps. After any changes you make, check temps. Even after adding a fan or 2 or 3, check temps.
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