Recommend a quiet exhaust [fan]

Cheetah · Post by **Cheetah** » Wed Sep 02, 2009 2:31 am

Hi there,

I want the quietest fan out there at the moment to exhust air (keep the air flow) in my passive system.

There isn't actually anywhere to attach the fan in the system so I will probably suspend it with bungee cord. Could probably fit a 140mm fan in there.

Bare in mind that it will be blowing air out of a gap which is 110mm x 70mm at max (this is where the PSU used to be)...I don't know whether it actually makes a difference (sound wise) if you are blowing air into the back of the case from a 140mm fan with only a 70mm gap for the air to escape.

What do you suggest?

Das_Saunamies · Post by **Das_Saunamies** » Wed Sep 02, 2009 4:32 am

I suggest a better case with proper exhausts.

But seriously, exhausting with a fan bigger than its intended exhaust 'port' will inevitably result in increased pressure, which means you'll need a fan with a strong motor so it can keep the CFM going. You should also duct it to make sure the hot air goes out and stays out.

I have personally been very happy with my Scythe S-Flex fans - these are the perfect, quiet but strong fans for me after countless tries with other types of fan, Scythe and others. The huge hub indicates a nice, robust motor and the bearings appear to be solid - they've even survived the case falling from hip-height once.

The first Noctua fans at least used to howl for me if there was too much backpressure from a restricted exhaust or insufficient intake. This was when I still used an Antec Sonata, happened in both I and II. Popping off a 5.25" bay cover solved the howling instantly, and so did lowering RPM. It was just frustrating watching what was supposed to be a 1200 RPM fan only spinning at 900-1000 RPM.

Cheetah · Post by **Cheetah** » Wed Sep 02, 2009 6:17 am

Just to show you the exhaust area (shaded in red.) Currently has an 80mm fan on there to exhaust the PSU air. I will be getting rid of the PSU completely so it will be an open segment. It also has the 40mm fan exhaust areas and I could punch through the serial port bits aswell...

I will also be suspending the new fan between 50-80mm away from the back of the case too (inside the case.)

Just wondering if what you said about pressure would still apply (and would still count as a main consideration.

Das_Saunamies · Post by **Das_Saunamies** » Wed Sep 02, 2009 6:31 am

I see this is not the typical ATX tower we're talking about here.

If I was in a situation like this with such restricted options, I would probably test things out with just an 80mm fan at first, since the hole already fits pretty snugly. I'd tape up extra holes in the back to prevent circulating the same air and intaking extra dust. Ducting I would still do, just to make sure all the hot air left the case and did not blow back. The performance of a small fan is already restricted, so you really have to make sure you get the most out of it. If the air's exit route matches fan size and there are no obstructions, motor and bearing considerations are not as crucial, as it is not a cooler (hot) or vertical (positioning) fan either.

It really depends on what is inside and how much airflow is strictly needed. Might not need to hack away at all!

If the 80mm fan proved to be enough with the PSU gone, I'd just look at the SPCR Recommended Fans list, as I haven't used such things in a long, long time. Suspension feels a bit overkill, a good fan grommet or a set of silicone studs will keep any a good fan from rumbling.

Cheetah · Post by **Cheetah** » Wed Sep 02, 2009 9:21 am

Das_Saunamies wrote:It really depends on what is inside and how much airflow is strictly needed. Might not need to hack away at all!

Thanks for the reply.

Personally, I think i could probably live without a fan at all but after reading on these forums it was suggested that I should have a fan just to ensure that there is at least some airflow through the case.

Details of my system can be found in this thread.

Das_Saunamies · Post by **Das_Saunamies** » Wed Sep 02, 2009 9:27 am

Airflow is essential for component life - manufacturers count on there being some, so the recommendation was a sound one.

The rig looks indeed cool enough to make do with whatever airflow is provided by basically any kind of fan. I can heartily recommend replacing little mobo fans with passive cooling, was very pleased with the results on my Asus A8N-E Deluxe. I used a Zalman product that had even better cooling power than expected, no heatpipes or anything.

Cheetah · Post by **Cheetah** » Wed Sep 02, 2009 9:37 am

Thanks for the quick replies.

Based on what you have said previously, do you recommend that I tape up the 40mm fan holes/grill on the back of the case AND the holes on the sides of the case and rely on the intake holes on the front of the case to maintain the airflow?

Or would that cause more sound - with the air squeezing through those small holes? (based on your experiences) Or is it simply the case of trial and error?

Das_Saunamies · Post by **Das_Saunamies** » Wed Sep 02, 2009 9:47 am

Well you do need air intake, so I would leave the front and sides be. At least when the cool air comes from over there, it will travel over the hot components and help in cooling them. The front looks so restricted that you are definitely doing the right thing leaving the sides open, although it is always a case of trial and error - always keep an eye on temperature readings after changing your system (HDDs are good indicators)!

I personally recommend taping up excess holes in the back because they are obviously meant to be exhausts (or something else entirely). If you created a negative pressure inside the case (as you will with just an exhaust fan), they would act as intakes, simply circulating air from the back through the exhaust fan and out back again without cooling much - if anything - which would be detrimental to the flow from the proper intakes.

I have never had intakes "whistling", but I am familiar with the phenomenon from driving a Volkswagen Polo at high speeds. Would not want that with a PC.

Cheetah · Post by **Cheetah** » Thu Sep 03, 2009 3:33 am

Right OK.

Did some testing today. Admittedly it was outside the case but I see your point about airflow.

What I did was replace the HSF that was on the chipset with the Passive Northbridge cooler I got. Booted up in the bliss of silence. Checked the temperatures and they were very HIGH. Touching the heatsinks on the northbridge cooler and the cpu heatsink - they were hot to the touch.

I didn't realize but the old little fan on the chipset actually cooled the CPU aswell!

Anyways, the CPU core temperatures were all around 45*C.

So what I did was balance a fan blowing air away from the heatsinks. This was positioned about 80mm from the heatsink of the chipset.

I let the system run for a little bit and the temperatures of the CPU (thats the smaller heatsink) when down to 28*C.

The point of all that was for people that are reading...airflow is important and hopefully that shows it. In the confines of a case I think the results may even be better and the fan I have balanced now will be sucking all the ambient air in too.

(All temperatures are taken at idle)
================

Am I right in saying that the more air a fan pushes the louder it is?

Cause what I am going to do is seal up all the vents on the back as suggested before and get an 80mm fan (as that can fit already) that runs at 1000rpm or less to blow air out of the case.

What I will do is have this connected to the motherboard so I can have it only run when needed.

Das_Saunamies · Post by **Das_Saunamies** » Thu Sep 03, 2009 4:05 am

Yeah, definitely always need one fan blowing in any type of regular setup. Good thing you're up for the tests, so you can see the results for yourself. Totally passive (and effective semipassive) cooling needs massive 'sinks and ingenuinity with heat conduction by means other than air (see Zalman TNN cases for example, the whole case is a heatsink and there's plenty of heatpipes).

Some people have had nice experiments and experiences with convection, but I wouldn't go that far - there are plenty of silent fans that will provide much better cooling with little to no interference in soundscape. Regarding the relation between "moving air" (CFM) and noise (dBA), it's not that clear-cut, as the motor and bearing noise have to be factored in as well, especially if there is restriction in the air's path (small exhaust/intake, corners, uneven duct). You also have to remember that volume isn't everything, the character of the sound matters a lot: a nasty ticking(early Noctua 800) or buzz(old Noiseblocker 120mm) can ruin an otherwise quiet fan's noise characteristics. I haven't found any Scythe or Noctua fans that vibrated too much if fastened properly. Old Noiseblockers with brittle plastic had some of that, both from frame and blades.

Sounds like your plans are made. I'd say it's good stuff as long as there is one fan running at all times, because not all components have thermal sensors (VRMs being the most prominently mentioned ones) that could tell a fan when to spin up. Keep an eye on the thermal readings and best of luck on your quest for silence!

Cheetah · Post by **Cheetah** » Thu Sep 03, 2009 8:45 am

What are SPCR's thoughts on a fan like the Sharkoon 80mm Silent Eagle 1000rpm.

The airflow is quoted as very little at only 11.4CFM, but it is also quoted at 8.9dbA, which I hope means inaudible to the human ear.

Is that airfow enough though?

Das_Saunamies · Post by **Das_Saunamies** » Thu Sep 03, 2009 3:29 pm

Sounds like very little... I'd rather consider the Nexus in the Recommended Fans list.

Cheetah · Post by **Cheetah** » Thu Sep 03, 2009 3:54 pm

I will have a look at that fan, but that article is 2 years old so has anything else come out in that time which is better?

Das_Saunamies · Post by **Das_Saunamies** » Thu Sep 03, 2009 4:19 pm

I've been surprised so many times to see how little things change or indeed improve on the silent front.

The last small-fan development was indeed those "golfball" fans from Sharkoon, but that's it I guess. Everything's moved into the bigger sizes, and now they're going crazy with the 135mm, 140mm and 200mm and above!

If these bigger S-Flex fans are anything to go by, I would say the small ones are definitely worth a look, airflow and silence-wise.

audiojar · Post by **audiojar** » Thu Sep 03, 2009 6:31 pm

Basically, the bigger the fan the better. Larger fans have to spin slower to produce the same airflow. Slow spin = less noise. If it is possible to mod the case (like cutting out some of the pack panel to make the hole for the fan bigger) so you can fit a 120mm fan then that would help you a lot.

When looking at noise levels (rated at dBA at 1m) something like 8dB is going to be well below your background level (for example, the anachoic chamber they use to test gear in here has an ambient of around 10-12 dB I believe). So if that is truly the level of the fan then it's pointlessly quiet, you could spin it faster and still not hear it. Something around 20 dB is still pretty quiet. Many people will buy the faster models of a fan and under volt it to slow it down. That way you can play around with different speeds/noise levels.

Cheetah · Post by **Cheetah** » Fri Sep 04, 2009 2:54 am

If I did decide to mod the case (which I am seriously thinking of doing now.)

Which fan would you go for?

I mean something like this is already pushing twice as much air for the same noise level rating.

EDIT: or even this which seems to be even quieter.

Also been looking at the Noctua S12-800; this one

new2spcr · Post by **new2spcr** » Fri Sep 04, 2009 6:08 am

Cheetah wrote:If I did decide to mod the case (which I am seriously thinking of doing now.)

Which fan would you go for?

I mean something like this is already pushing twice as much air for the same noise level rating.

EDIT: or even this which seems to be even quieter.

Also been looking at the Noctua S12-800; this one

I've tried several popular 120 mm fans (Noctua, Scythe slipstream, Scythe S-flex, Nexus Real Silent fan) and I can say I'm happiest with the Scythe S-flex 800 rpm IMHO, while not perfect it moves sufficient amount of air while being quieter than others... undervolted ofcourse. I've read several reports saying the Noctua's weird looking fanblades produce some noise many aren't comfy with.

audiojar · Post by **audiojar** » Fri Sep 04, 2009 4:46 pm

IMO Scythe has a few good lines. Slipstreams are the best value, probably the best value fan overall actually. S-Flex and Gentle Typhon are a bit more and have some interesting designs.

Basically, trying to find "the best" fan isn't really worth it (or possible). Just get what appeals to you most out of one of the best.

Cheetah · Post by **Cheetah** » Sun Sep 06, 2009 6:55 am

Did some modding today of the case ready for when I receive my fan.

Here is what the rear of the case looks like:

As you can see, I'm not the best of modders or the cleanest but I think it should work ok. The gap is a little too big (long) as you can see but that had to be done due to the way the case is built.

I will make sure any gaps/holes in the back are covered when I fit the far to ensure the hot air doesn't get back into the case.

Went for a Noctua fan in the end because I could pick one up cheaply.

SebRad · Post by **SebRad** » Sun Sep 06, 2009 12:20 pm

Hi, I've read good things about Scythe Gentle Typhoon fans. Come in 92 & 120mm sizes and various speeds.
Regards, Seb