Bottom intake vs. front intake ?

Thomas · Post by **Thomas** » Tue Apr 28, 2009 5:19 am

I'm somewhat pleased with my current system, but I find that too much noise escape through the front of my P180.

Will it help swapping for a case with buttom intake?

I guess a lot depends on the details, so here they are:

AMD 4850e/Asus Triton 75/S-Flex/C'n'Q spinning @500 rpm most of the time
Gigabyte GA-MA78G-DS3H/IGP/Kingston 4GB
I have a Nexus 12cm in the upper front intake, spinning @500 rpm and a S-Flex @500 rpm in the rear exhaust. Upper fan exhaust is blocked, just like the rear holes around PCI / PCU
Seasonic S12 380/S-Flex @500 RPM
2 x Hitachi 5K160 2,5"/Scythe Quiet Drive in lower drive cage
1 x optical drive
Inner front doors for airintake are removed

Hopefully, I can buy a Phenom II x4 within a few months, and at my opinion, my current system cant improve cooling by much, without sacrifising quietness

Untill recently, I didnt have the Nexus as intake fan, but I discovered that if the system is fully loaded for about 5 minutes, the CPU goes the thermal run away route. The Nexus improved cooling a lot, but also added more noise

I havent cut the grills, and I suspect that the Nexus aint as quiet, as when it was new.

The alternative I'm considering, is getting a Enermax CS 718 (=Temjin TJ06), and block the front intakes, cut a 12 cm in the buttom for CPU cooling, and opening all the PCI slots for intake for for system/HDD/PSU cooling. And suspend the two drives in the standard drive cage.

What do you think? Will the fan noise from the CPU department just be reflected by my wood floor to my ears? Or is it worth blocking the front and open the buttom?

Thanks.

LodeHacker · Post by **LodeHacker** » Tue Apr 28, 2009 6:12 am

To Nexus' defence I have a very hard time figuring out whether my Nexus fans make noise at all @ 5.5V so lowering the volts can help a lot in lowering the overall acoustic footprint but it will directly affect cooling performance.

On the other hand let me say it straight, a bottom intake is defective by design. Need I say more than Nexus Breeze? I have had personal experience wit the Breeze and the most problematic part of the whole setup was the bottom intake. It really is very bad design. No matter how good it looks on paper the real figures are clear and a fan at the bottom of the case is not good and does not really help overall airflow.

judge56988 · Post by **judge56988** » Tue Apr 28, 2009 7:48 am

LodeHacker wrote:
On the other hand let me say it straight, a bottom intake is defective by design. Need I say more than Nexus Breeze? I have had personal experience wit the Breeze and the most problematic part of the whole setup was the bottom intake. It really is very bad design. No matter how good it looks on paper the real figures are clear and a fan at the bottom of the case is not good and does not really help overall airflow.

I've had a Breeze for 5 years, bought before I heard of this site btw.

Since learning more about the silencing thing I've thought that the weak point of the Breeze was that all the hot air gets exhausted out through the PSU. I'm curious to know more about why you think bottom intakes are so bad by design? How was it problematic for you?

I've seen a few builds here where people have blocked front intakes and replaced them with new bottom intakes.

I'm still new to this silencing and have only built a shuttle pc for my daughter since the Breeze, so I'm interested, not criticising you!

My thoughts are that front intake cools HDD's better but may leave the graphics card in a bit of a dead zone, while a bottom intake may be the opposite.

LodeHacker · Post by **LodeHacker** » Tue Apr 28, 2009 8:28 am

The contra of the Breeze in regard to the bottom intake (my experience with it):
- Graphics card will have a harder time getting fresh air -> need the fan spinning faster -> more noise.
- Bottom intake fan will block a great deal of internal motherboard connections -> unnecessary reconstruction of the whole system required.
- Longer PCI cards (read: most PCI cards) are impossible to install in the last PCI slot because of the bottom intake fan.
- HDDs will have a harder time get cooled (if multiple HDDs are installed) -> need for a separate HDD cooling procedure arises.
- Because the fan is at the bottom, higher case feet are required and thus internal case space is reduced -> unnecessarily complex approach for a single intake that takes space, did not fit under my desk!
- Without filters the bottom intake is pushing everything but air to the system -> dust gathers up very quickly even if the room is regularly vacuumed.
- With filters the fan pushes air slower than a turtle walking in a desert -> need for raising fan speed arises -> system noise gets unbearable just to keep that single graphics card in a safe temperature range.

----

So for me a bottom intake is seriously bad design. Throw in a couple of Nexus' @ 5.5V at the front and you have lots of air moving around and with a simple filter you get away dust for a long time before needing to vacuum (blow) the case!

Thomas · Post by **Thomas** » Tue Apr 28, 2009 9:37 am

I forgot to mention, that I'm using the onboard CPU fan controller for controlling both the CPU and exhaust fan, and when the CPU is under heavy load, both these fans spins at around 1100 RPM, and they're still having a hard time keeping the CPU cold.

The Nexus intake fan is still around 500 rpm in this situation.

Thomas · Post by **Thomas** » Tue Apr 28, 2009 9:39 am

LodeHacker wrote:To Nexus' defence I have a very hard time figuring out whether my Nexus fans make noise at all @ 5.5V

That's where my Nexus is (@ 5-6 volt), seems to confirm my Nexus is no longer good...

Thomas · Post by **Thomas** » Tue Apr 28, 2009 9:52 am

Overall, I think the Nexus has other and bigger problems, than the buttom placed fan...

However, I'm not considering a Breeze, but a Temjin TJ06 (SPCR review here) in disguise as a Enermax CS 718.

LodeHacker wrote:- Graphics card will have a harder time getting fresh air -> need the fan spinning faster -> more noise.

As mentioned, I use my mobo's Integrated Graphic Processor (IGP)

LodeHacker wrote:- Bottom intake fan will block a great deal of internal motherboard connections -> unnecessary reconstruction of the whole system required.
- Longer PCI cards (read: most PCI cards) are impossible to install in the last PCI slot because of the bottom intake fan.
- HDDs will have a harder time get cooled (if multiple HDDs are installed) -> need for a separate HDD cooling procedure arises.

These dont apply to the Temjin TJ06.

LodeHacker wrote:- Because the fan is at the bottom, higher case feet are required and thus internal case space is reduced -> unnecessarily complex approach for a single intake that takes space, did not fit under my desk!

Temjin TJ06 comes with pretty high feet as standard, and the case is huge, so there's plenty of space internally

LodeHacker wrote:- Without filters the bottom intake is pushing everything but air to the system -> dust gathers up very quickly even if the room is regularly vacuumed.
- With filters the fan pushes air slower than a turtle walking in a desert -> need for raising fan speed arises -> system noise gets unbearable just to keep that single graphics card in a safe temperature range.

Hmmm, I dont see why filters should be worse to buttomplaced fans, than to front placed ditto?

hybrid2d4x4 · Post by **hybrid2d4x4** » Tue Apr 28, 2009 9:55 am

Lodehacker > He's already running the fans @ 500 RPM. If they're like slipstream 1200RPM fans, that's already considerably lower than 5.5V, so what you're suggesting would be a step in the wrong direction...

Thomas > If your CPU heatsink is reasonably close to the rear exhaust (and the fins are parallel to the airflow), then the S-Flex on the CPU might be unnecessary. What I'd try is take the Scythe off the CPU and try it as an intake instead of the Nexus which you seem to suspect is worn.

Actually after having a look at that cooler, it seems like the CPU temp issue is because that cooler isn't designed to work at low airflow and it relies on airflow perpendicular to the flow from the intake/exhaust. You can still try the swap I suggested above but I suspect getting a cooler more suited to your application will be the ultimate solution here (read: tower cooler).
Your CPU is far from being a furnace, and you don't have a hot vid card in the mix, so you shouldn't need 4 fans in that system...

LodeHacker · Post by **LodeHacker** » Tue Apr 28, 2009 10:50 am

Do note though that I didn't list problems with a bottom intake, but problems I experienced with the now-out-of-production Nexus Breeze and its bottom intake. I never had a Temjin case so can't really judge but on my part I have had enough of all airflow related problems I might as will go to the dark side and get a reasonable water cooling set

Thomas · Post by **Thomas** » Tue Apr 28, 2009 9:36 pm

hybrid2d4x4 wrote:...but I suspect getting a cooler more suited to your application will be the ultimate solution here (read: tower cooler).
Your CPU is far from being a furnace, and you don't have a hot vid card in the mix, so you shouldn't need 4 fans in that system...

I think this nails it - heck, even with a Temjin, I would need to swap the CPU cooler for optimum performance...

Thanks