120mm Fan suggestions and general case airflow design help

[Cynor]

Hi all! My current build is sitting in pieces due to circumstances/issues, and to fix that I'm likely getting a new video card. I've decided that noise is a factor for me and supposedly the ACX style coolers are good for low noise. However, I also read that they need pretty good case airflow to work well. As such, I'm thinking that maybe now could be a good time to take the mis-matched hodgepodge of fans I have (most of which are pretty old) and get new ones that are nice and (hopefully) quiet.

The case I have is, to put it bluntly, a monster. It has 7 (SEVEN!) 120mm Fans on it and is an 18x18x18 inch Cube. I speak of the U2-UFO from Mountain Mods. There are 2 distinct sides to the case, the Mobo/Radiator side and the Drive Bay side.

The first side has a 3x120 Radiator on the front as intake, and a single 120 on (upper) back as exhaust.
The second side has a single 120 intake (lower), with 2 (upper) exhausts that also hold the HDDs for the system via fan mounts.

As you can see, that's a lot of fans to work with and noise can add up quick. Not to mention I wonder a little about the airflow in the case with all the mis-matched fans.

I know a few are Antec Tri-Cools, but looking up those specs on RPM/CFM/DB it's like holy cow they SUCK. I'm currently considering some Scythe Gentle Typhoons, as even though they are a bit pricey, the performance seems to be a ton better. I think I keep the Tri-Cools on low, which means they are moving like 40CFM each @ 25db. The Scythes can do MORE than that at 9 db! Or for roughly same noise (and I really think main noise in my case in video card) 85 or almost 100 (if I'm running on medium instead of low).

One has to hope that would vastly up air movement, which would be good for everything in the case. Especially since by going with water you lose some of that airflow from the CPU cooler.

So if anyone has any suggestions on some good, quiet, fans; a suggestion on mounting/speeds (like place a higher CFM/RPM on drive bay upper to try to pull air from bottom of case); or whatever I'd really appreciate it.

 

[Calculatron]

The general rule for case airflow is that the bottom half of the case (front, sides) should be intake, and the top should be exhaust.

On places with restrictive airflow, like heatsinks, radiators, and harddrive bays, you want fans that produce more static pressure. This ensures that the air goes where it needs to.

If you want good fans, expect to spend around 15 dollars a pop, give or take some. Was there a particular budget you were hoping to maintain, or do you want to know the full line of options?

 

[Cynor]

TBH, I don't really have a budget in mind. I mean I don't want to spend too much, but I was thinking that each fan would be between 10 to 15 to maybe 20 USD per. By far the biggest thing I'm worried about is noise, but also keeping good performance and setting it up right. Which is not something I've really done in the past.

Just to clarify that though... I've obviously set them up and I know the general rules of front/low in and high/back exhaust and stuff. I'm talking more about the whole CFM, negative and positive air pressure, how case design effects that, restrictive areas like the radiator...

 

[Calculatron]

On subject of case fans:
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100006519%2050013802%2040000573%20600035590&IsNodeId=1&Manufactory=13802&name=120mm&SpeTabStoreType=1

Cougars offer a great balance of being quiet, paired with good performance, all at a decent price.

Arctic Cooling makes good fans as well, which will be (slightly) quieter, but won't perform as well on radiators: http://www.newegg.com/Product/Product.aspx?Item=N82E16835186033

Tom's Hardware did a number of articles some years ago on the subject of case airflow, they may be worth reading: http://www.tomshardware.com/reviews/cooling-airflow-heatsink,3053.html

Positive and Negative pressure aside, the general rules already mentioned still apply: restrictive areas require more static pressure. Any physical obstructive, or surface, that air touches will cause a turbulence and a drastic slowdown of airflow. More pressure helps to combat this. (So make sure you have good cable management.)

Positive and Negative pressure is both a subjective preference, and situation dependent aspect. In my hot little office, where I also have fur-shedding pets, negative pressure not only yields me better performance but makes sure my internals don't get as cluttered with dust and other unsavory bits. I have other friends who swear by using positive. To find the truth, ultimately you'll have to experiment.

 

[Cynor]

Any physical obstructive, or surface, that air touches will cause a turbulence and a drastic slowdown of airflow. More pressure helps to combat this. (So make sure you have good cable management.)

Is there any way to really test/manage this for the whole positive/negative airflow? After reading around, looking at various sites/reviews, and the fan roundup here, I think I know what fans I'm wanting for the intakes. Namely some Nosieblocker e-loop b-12-3s. These are rated at 1900 RPMs, 71 CFM, and just under (by .003) 2mmH2O Static Pressure. I plan a slightly lower speed one for (51CFM) for the more open intake. Lots of CFM there.

Now I know from the fan roundup number 2 here that obstructions (I think they just used like a fan filter or two?) really lowered the CFM on fans, so with the radiator there, along with maybe running slightly lower on a fan controller, it's not going to be the full 265 CFM available.

I do like the looks, sound levels (not that they mean much sometimes lol), and static pressure on the cougars, especially given 2 of the 3 exhausts have to pull over/around the HDDs/SSDs. But considering the non PWM versions are only rated at around 60/65 CFM that really doesn't balance well. Considering I think I want negative pressure, that means I'm short about 70-85 CFM (quick and dirty mind math), before any obstructions change the CFM.

So I guess the question kind of becomes, do I try to balance CFM ignoring obstructions/Static Pressure? But I know I'll be losing some from the rad and cables and HDDs. If I try to keep about the same static pressure on all fans will that balance it out?

 

[Calculatron]

Well, you already have the case, with fans. Turn the intakes to low, and exhaust to high, and vice-versa, and be sure to record the results.

Here are some pertinent round-ups/tests for you:

http://martinsliquidlab.org/2013/05/07/fan-testing-round-12/

http://www.youtube.com/watch?v=rFzqynEOXlA
http://www.youtube.com/watch?v=opEGl_eoD4w
http://www.youtube.com/watch?v=gkoGccjRVSs