Will positioning fans further inside the case reduce noise?

Enclosures and acoustic damping to help quiet them.

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Silent but deadly
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Will positioning fans further inside the case reduce noise?

Post by Silent but deadly » Fri Jan 09, 2015 9:23 am

I'm planning to migrate my current non-silence focused build to a new case (Fractal Design XL R2) and attempt to build the quietest build I can. There are a couple of things that I haven't made my mind up about though. My current rig is as follows-

PSU - Corsair AX760
CPU - i5 2500k
Heatsink - Corsair H100i with 2x 1850rpm Gentle Typhoons [EDIT] which I'll almost certainly replace with a Scythe Kotetsu.
Mobo - Asus P8Z77-V Deluxe
GPU - Asus GTX 670 DirectCU II TOP
SSD's - 2x 256gb Samsung 830's
HDD's - either a 2TB or 3TB WD Green
Case fans - 3x Noiseblocker B12-2's (thanks for helping me choose these MikeC)

The two questions rattling around my mind are-

1. Would positioning the front fans further inside the case help reduce noise? Let me explain, I plan to remove both HDD cages and mount the fans to the radiator mount rather than in the removable fan filter (as can be seen in this image - http://images.bit-tech.net/content_imag ... lr2-8b.jpg). The main reason for this is to make the fan filter much easier to clean and also to give the fans a little more room to breath and to get them that little bit closer to what I want them to cool but would it also help reduce noise levels? And, if I was to take it to the extreme, would I see further gains using something similar to this radiator shroud (http://www.frozencpu.com/images/product ... pa-280.jpg) to move the fans even further into the case and thus closer to my components?

2. My second question regards my Corsair H100i. The top vent of the XL R2 isn't filtered, so is there any advantage in terms of noise level with the H100i exhausting unfiltered out the top vent vs. intaking air through an aftermarket filter?
Last edited by Silent but deadly on Mon Jan 12, 2015 9:09 am, edited 1 time in total.

MiniMatt
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Re: Will positioning fans further inside the case reduce noi

Post by MiniMatt » Sat Jan 10, 2015 5:11 am

1. Regarding positioning fans deeper within the case. Testing would show for sure but my hunch is that you'd gain no noticeable acoustic benefit at modest fan speeds. Potentially more problematic could be that moving the intake fans away from their filters you incentivise them to pull air from the path of least resistance - which could be unfiltered screw holes etc, and could set up non-optimal through-case air flow.

2. The top and rear vents on a case are generally going to be better utilised as exhaust vents rather than intakes.

edh
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Re: Will positioning fans further inside the case reduce noi

Post by edh » Sat Jan 10, 2015 7:13 am

More fundamentally why are you trying to silence your computer by changing case? Why not change components inside it instead? The case itself makes little difference to noise levels if you already have noisy components. I would swap the H100i which is never going to give you a decent sound floor for a Noctua NH-D15, Thermalright HR-22, Scythe Kotetsu or similar big tower cooler. Also replace the stock cooler on your graphics card with an Accelero Xtreme or similar aftermarket graphics cooler. Then soft mount your hard disks. This will have a far bigger effect than changing case.

xan_user
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Re: Will positioning fans further inside the case reduce noi

Post by xan_user » Sat Jan 10, 2015 12:49 pm

ive built a few rigs with single a fan where the HDD rack would normally be.
but...its still more important to have quiet parts inside, than to relying on a case, or fan placement to make a difference.
i wouldn't really suggest (it in) a water cooled rig tho.

Silent but deadly
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Re: Will positioning fans further inside the case reduce noi

Post by Silent but deadly » Sun Jan 11, 2015 10:08 am

MiniMatt wrote:1. Regarding positioning fans deeper within the case. Testing would show for sure but my hunch is that you'd gain no noticeable acoustic benefit at modest fan speeds. Potentially more problematic could be that moving the intake fans away from their filters you incentivise them to pull air from the path of least resistance - which could be unfiltered screw holes etc, and could set up non-optimal through-case air flow.

2. The top and rear vents on a case are generally going to be better utilised as exhaust vents rather than intakes.
1. I'd be sure to seal up any problematic gaps but with the fans mounted as if they were radiators, there would only be a small gap around the fans. They'd have to pull air from inside the case, against their own flow of exhausted air, in order to pull in unfiltered air. The only part of the case that acts as an intake and that isn't filtered or covered by one of Fractal's “moduvents” is the 5.25” bay covers and I have plans to filter or block them depending on whether I keep a mechanical drive in the new case. I will of course give the case a more detailed examination to make sure unfiltered air isn't an issue and I'll also block the small gaps around the fans just to be sure.

2. H100i intake vs exhaust is probably a non-issue now (see my reply to edh below).

edh wrote:More fundamentally why are you trying to silence your computer by changing case? Why not change components inside it instead? The case itself makes little difference to noise levels if you already have noisy components. I would swap the H100i which is never going to give you a decent sound floor for a Noctua NH-D15, Thermalright HR-22, Scythe Kotetsu or similar big tower cooler. Also replace the stock cooler on your graphics card with an Accelero Xtreme or similar aftermarket graphics cooler. Then soft mount your hard disks. This will have a far bigger effect than changing case.
Let me tackle the issue of components first. Aside from the H100i, all the other components would be at home (and have been used) in a Puget Systems rig. I do intend to replace the H100i should it's pump prove to be too loud. Thanks for mentioning the Scythe Kotetsu, I'd some how managed to miss SPCR's review of it. It's what I'll get if the H100i proves to be too noisy. In regards to the GPU, I bought the Asus GTX 670 DirectCU II TOP as it has great performance but also has one of, if not the, quietest stock coolers of any GTX 670. To quote Lawrence Lee's [url+http://www.silentpcreview.com/ASUS_GeForce_GTX_670]SPCR review[/url] of the non-TOP version of the Asus GTX 670 - "The DirectCU II cooler is the cherry on top, making it the coolest and quietest high-end graphics card we've ever tested that wasn't using third party cooling". The card was also used by Puget Systems (I believe as the default GTX 670 in their builds). I know it could be quieter with the help of an aftermarket cooler but it's quiet enough for me when it's idleing and I now very loud under load... put it this way, if it's the loudest thing in my rig, I'll be content (I'm usually wearing headphones when the GPU is doing anything taxing anyway).

In regards to the hard disks. My intention is to have my two SSD's and possibly a single WD Green, that I'll soft mount in the 5.25” bays. I'm building a home server so data storage will be network based for the most part. I've yet to try soft mounting the HDD's in my current case but removing them all together does make a massive difference (not least showing me just how damn loud the H100's pump is and how much my current case rattles).

So why get a new case if I can eliminate most of the noise in my current one? Well, there are several reasons but the three main ones are the size of the case, the HDD cages and the many other more minor reasons that all add up (but I won't bother going into/waffling on about them).

I know the XL R2 is still on the large side but it'd save me so much space compared to my current case and I'd be able to house it in a spot where my current case is too large to fit. I'm like an old person moving out of a spacious house and into a much smaller house. I'm giving up the extra space and the chance of building some crazy rig but I doubt I'll ever get round to it due to recent changes to my life. There's also the lower HDD cage in the XL R2. As I said, I'm building a home server, which is also in an XL R2, and I'm in need of another lower HDD cage. Fractal's spares website is always out of stock, Puget used to sell them but don't anymore (the international shipping would probably be too much anyway), I've been unable to find one on eBay and have had no luck sourcing a used one from the members market on the various forums I frequent. A new case would also kill all the other birds with on stone. This build is still in the planning stages but I like to get my ducks in a row. I'm gonna carry on looking for the HDD cage but if I can find one in the next few months, I'll have a plan in place.

xan_user wrote:ive built a few rigs with single a fan where the HDD rack would normally be.
but...its still more important to have quiet parts inside, than to relying on a case, or fan placement to make a difference.
i wouldn't really suggest (it in) a water cooled rig tho.
If I had the money to water cool my PC... I still wouldn't. I'd love have a water cooled rig, it's why I bought my current case but the money would be better used elsewhere (e.g. on my home server). I'm trying to spend as little as possible and as it stands, all I think I need is the new case and a new heatsink, the cost of which would be covered (and then some) by selling my current case.


[EDIT] Fixed hyperlink and a smelling pistake.
Last edited by Silent but deadly on Mon Jan 12, 2015 9:07 am, edited 1 time in total.

MiniMatt
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Re: Will positioning fans further inside the case reduce noi

Post by MiniMatt » Mon Jan 12, 2015 12:08 am

1. I'd be sure to seal up any problematic gaps but with the fans mounted as if they were radiators, there would only be a small gap around the fans. They'd have to pull air from inside the case, against their own flow of exhausted air, in order to pull in unfiltered air. The only part of the case that acts as an intake and that isn't filtered or covered by one of Fractal's “moduvents” is the 5.25” bay covers and I have plans to filter or block them depending on whether I keep a mechanical drive in the new case. I will of course give the case a more detailed examination to make sure unfiltered air isn't an issue and I'll also block the small gaps around the fans just to be sure.
I'm not entirely sure I've quite grasped what you're getting at, just to be clear, below is my rough approximation of what a typical layout might look like with 2 of the noiseblocker case fans as intakes, 1 as an exhaust, the two fans attached to the H100i radiator as exhausts:

Code: Select all

               H100i
              Exhaust

               ^ ^ ^
               | | |

         ---------------------
         |   |  | |  |       |
         |   ---- ----       |
  Case   |-|                 |
     <-- | |                 |
 Exhaust |-|   CPU           |
         |                   |
         |                 |-|
         |             HDD | | <--
         |-------          |-|  Case
         |  GPU        HDD   |
         |                 |-|  Intake
         |             HDD | | <--
         |                 |-|
         ---------------------
Would that be essentially correct? And what you're considering is moving the two front intake fans inside the case, to a space between the hard drives and the motherboard?

EDIT:

What I was getting at with my first post is that in the typical setup drawn above, you've likely got a fractional negative pressure inside the case. That is, with more exhaust than intake you're creating a slight vacuum inside the case, and that air deficit is made up by air rushing in from wherever fluid dynamics tells us it'll come from - which is essentially every little gap. I'd question the feasibility of essentially making a case air tight other than through the paths you deem acceptable (ie filtered gaps) - it'll come in through USB ports, through screw holes, through the CD tray etc.

By moving the front fans away from their filters and into the case proper, you increase the vacuum within the case - you're now looking at three exhaust fans and no discernible intake fans - rather those front fans will now circulate whatever air they've got from wherever they can get it. The only effect I'm reasonably sure of is that this will increase the air pulled in from unfiltered sources and modestly increase the amount of dust accumulating inside the case.

It *may* also improve acoustics - but my hunch would be that at idle and low-moderate load such an effect would be negligible and unnoticeable. It *may* improve cooling by moving fans closer to hot components.

The (minor) concern is that it *may* actually hinder cooling (thereby also hindering acoustics as everything spins faster). In the typical layout drawn above you've got a fairly straight, predictable air path for the bulk of the air flowing through the system - bottom front to top back. If you add unpredictability to where that intake air is coming from it's *possible* that eddies get set up whereby air does a couple of laps before getting exhausted.

It's important to note the heavy emphasis of *may* and *possible* in the above two paragraphs - testing is the only way to see for sure because the variables are just waay too unpredictable. My hunch, and that's all it is, would be that any acoustic benefit would be unnoticeable, any cooling benefit would only be in the order of a couple of degrees, any cooling hindrance would also only be in the order of a couple of degrees, and any dust increase rates will only be in the order of a couple of percent.

Silent but deadly
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Re: Will positioning fans further inside the case reduce noi

Post by Silent but deadly » Mon Jan 12, 2015 9:06 am

To clarify exactly what I mean, let me explain why I want to mount the fans further inside the case. In the following image, I have circled the three things.

1. Plastic, tool free retention clips that hold the fan in place.
2. Guide pins that act as screws.
3. Mounting holes for radiators.

Image

The fan housing also acts as a fan filter but the plastic it is made of is rather hard and inflexible. In order to properly clean the dust filter, you have to remove the fans... when I installed them in my other XL R2, I was almost certain that I'd snap the plastic. That's coming from someone whose always very gentle with their hardware. If I had to remove the fans everytime I wanted to thoroughly clean the dust filter, it (or I) would snap eventually. I should have circled a fourth thing, the fan cable. You can tuck it away and tie it down because each time you want to clean the filter, you'd need to untie it in order to provide enough slack.

If I was to mount the fans to the back of the metal plate (using the "3. mounting holes) as if the fans were a 240mm radiator, that'd let me completely remove the front fan filter when I wanted to clean it and I could manage the fan cables. This was what led me to asking if there was a noise benefit when moving the fans further into the case. I thought that 'if I mount them were the radiator normally goes, could I take it a step further and use a fan shroud to move them even deeper into the case'.

On the subject of unwanted/unfiltered airflow. If I were to block up the small gaps left around the fans (the edges of which would be similar to that of the rounded metal lip of the HDD cages in the picture above), then holes left in the front of the case would either be covered by the fan filter (such as the small rectangular holes seen to the left and above/below #3 in the picture or would have a sufficiently convoluted route the the intake side of the fans that I would hazard a guess that they'd not be an issue. I will of course test my hypothesis if I get the case.

In regards to the H100i, to quote my reply to edh "I do intend to replace the H100i should it's pump prove to be too loud. Thanks for mentioning the Scythe Kotetsu, I'd some how managed to miss SPCR's review of it. It's what I'll get if the H100i proves to be too noisy.". So, the issue of the H100i being exhaust or intake is probably sorted (as the pump is rather loud) and thus the issue of achieving positive pressure.

One last though, I'm also trying to find a way to convert three of the 5.25" bays into an intake using a very low rpm fan, so that when I decouple the HDD, it will at least get some directed airflow. This should also help with pressure but finding a fan mount/hdd rack that doesn't restrict space that I'd use for decoupling and is filtered with an easily removable/cleanable filter is proving difficult. I might have to resort to Macgyvering something up.

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Re: Will positioning fans further inside the case reduce noi

Post by xan_user » Mon Jan 12, 2015 9:20 am

another reason to consider fan(s) in the middle is that it might be possible to use a larger fan, than in the 'normal' position.

Silent but deadly
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Re: Will positioning fans further inside the case reduce noi

Post by Silent but deadly » Tue Jan 13, 2015 8:19 am

xan_user wrote:another reason to consider fan(s) in the middle is that it might be possible to use a larger fan, than in the 'normal' position.
That's a good point but it'd involve spending more money than I need to, I'd have to find a way to mount it/them without encountering issues with unwanted, unfiltered air intake and the fans I have (B12-2's) are already great. What I'm considering at the moment is trying my hand at making an angled fan mounting bracket. Puget Systems uses an angled fan, in their awesome Serenity Pro, to improve cooling and reduce noise.

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