Low air resistance, low fan speed, low noise technique

Katana Man · Post by **Katana Man** » Wed Nov 26, 2003 11:32 am

I've built hundreds of computers, and I've come to the conclusion, that using filters will keep the computer a little cleaner on the inside, but causes them to be louder. This is because you have to run the fans much faster to compensate for the poor air flow.

I've learned to go all or nothing. The day I discovered this is when I was holding a low speed 120mm fan in my hand. I had it blowing on my face so I could feel how much air it was blowing. While it was running, I placed a standard fan grill over it. I could not believe how much a simple fan grill cut down the air flow! It was then that I realized how much air flow resistance is produced from fan grills, case grills, case bezels, fan holders, and filters.

With this new knowledge, I built my D8000. For many hours, I tested with multiple combinations of fan grills, filters, bezels, fan speeds, etc. I carefully monitored temperatures and noise levels. The conclusion was very evident. The lowest temperatures and noise levels were obtained with the no filters, case grills cut out, and minimal finger guards (if any). With this combination, the fans can be turned way down, and the noise level and temps were at their lowest. The only disadvantage is more dust will accumulate inside the case. But over the last 4-5 months, strangely, the dust build up has not been that much more than if I had all of the filters in place.

The reason that I posted this is because there are many SPCR member's who don't want to commit to this technique fully. The top reasons I've read are:
1. They don't want to cut the case (cutting out the case grills and front bezel).
2. They think that noise escapes if you do cut the front bezel.
3. They don't want to clean the dust inside the case.

I can certainly understand these objections, but I just want to encourage you all to try this low resistance, low fan speed, low noise technique. It works well with cases with 120mm fans.

D8000 project

Chenbro 611 project

Supermicro 750 project

Beige LX-6A19 project (http://www.laddergames.com/images/bmt/IMG_3416r.jpg)

You can't hear these computers unless you stick your head under the desk. My wife used to come back to her computer after a few hours and forget if it's running. Since the monitor has gone black by then (due to sleep mode), she used to think the computer is off and hits the power button. I have now trained her to look for the lights or wiggle the mouse to verify that if the computer is actually on or off

That should give you an idea of how quiet this technique really is. Feel free to read this post with a grain of salt, but it works for me, and I thought I'd pass my findings along.

chylld · Post by **chylld** » Wed Nov 26, 2003 11:36 am

possibly the airflow isn't being restricted by the grill - maybe it's just being dispersed more? hence why you can't feel it blowing onto your face?

Katana Man · Post by **Katana Man** » Wed Nov 26, 2003 11:59 am

No. It's definately more than that. It slows the air speed down completely. Having a grill, filter, or bezel, etc. very close the the fan will also causes it to be louder as well. Temperatures also confirm my findings as well. Test it out, you'll see what I mean.

Bluefront · Post by **Bluefront** » Thu Nov 27, 2003 6:38 am

Up to a point I agree with you....however, if the filter area you are drawing through is large enough, the reduction in airflow and the increase in noise will be insignificant.

Imagine a filter the size of a 55 gallon drum....now put your little computer fan on top drawing through it. Do you really think there would be an airflow restriction?

The problem comes when you try to fit a large filter, but it is possible.

rear filter

another rear filter

really big auto air-filter

Here's another picture of that last filter. It gives a better idea of how big it is. IMHO this is the best filter setup I ever saw. It requires moving the PSU....no small deal.....but the location draws air right over all the hot parts. The exhaust fan (one 120mm) is on the bottom of the case. For all my own computers, this is my solution. No air restriction at all....

Katana Man · Post by **Katana Man** » Thu Nov 27, 2003 6:04 pm

I definately agree. Very practical, but these look pretty silly to me, so I'd prefer to go without

JVM · Post by **JVM** » Sun Dec 07, 2003 1:26 pm

Katana Man wrote:No. It's definately more than that. It slows the air speed down completely. Having a grill, filter, or bezel, etc. very close the the fan will also causes it to be louder as well. Temperatures also confirm my findings as well. Test it out, you'll see what I mean.

How about a filter in front of the air intake without a fan? By that I mean a front air filter on the outside of the intake as in the Sonata. What is your feeling about noise or air flow regarding that situation without a front fan?

Katana Man · Post by **Katana Man** » Thu Oct 07, 2004 5:50 pm

My feelings have changed on air filters. I now feel that they are unecessary. Let's face it, computers will get dust in them. It's not the end of the world. I don't know about you guys, but I have to go inside my computers (to replace a card, upgrade, or whatever else) a couple of times per year. Naturally, I'll look over the dust situation during those times. If the dust is heavy on the heat sink fins or elsewhere, I'll use a portable vacuum cleaner and have it resolved in a few minutes. I might vacuum a computer once, maybe twice per year. As my cousin would say, "No biggie!".

And furthermore, I have noticed no difference in dust buildup using stock case setups verses the low resistance, low fan speed, low noise technique.

Whenever, I have the time, I "gut" out these stock cases for the low air resistance technique. Let me give you an example. I'm currently working on an Compucase LX-6A19 for my father.
- A stock LX-6A19 case setup has 8 restriction pieces.
These include 1 front bezel, 1 filter, 2 case grills, 2 fan holders, 1 finger guard, and 1 PSU grill.
- My modified LX-6A19 case has only 2 resitriction pieces.
1 Modder's mesh grill, and 1 PSU grill.

This is a drastic reduction in air flow resistance! If you don't believe me, do the test yourself, run a 120mm fan at 5V with some restrictions in front of it, like finger guards or case grills, etc.. You can easily hear and feel the difference. My noise levels and temperatures have never been lower. I won't lie to you though, it takes work to do these modifications. I've already spent 4 hours on my fathers case and I'm just starting to finish it up now. The good news is, these cases far outlast the computer components inside. It's worth spending the time, especially for anyone who uses a computer often.

Bluefront · Post by **Bluefront** » Thu Oct 07, 2004 6:17 pm

My feelings on air filters hasn't changed. My house is as dusty as ever due to a large dusty parrot....who flaps dust everywhere. And I don't like dusty computers. So I treat air filtration just like quieting techniques.

Sure you could have a noisy,dusty computer. Chances are good it will work just fine. But I don't want either, and it is possible to go quiet and clean.....but more difficult. Going clean is mostly a DIY mod, more difficult because you can't just buy a clean computer, or even clean parts.

If your computer runs clean without filters, consider yourself lucky.

sthayashi · Post by **sthayashi** » Thu Oct 07, 2004 7:42 pm

Katana Man wrote:If the dust is heavy on the heat sink fins or elsewhere, I'll use a portable vacuum cleaner and have it resolved in a few minutes. I might vacuum a computer once, maybe twice per year.

Question: Are you're concerned at all about static build up and discharge with a vacuum cleaner (even a portable one)?

Katana Man · Post by **Katana Man** » Thu Oct 07, 2004 7:55 pm

I use a long plastic extension on the vacuum cleaner and I can clean up the case in probably 30 seconds. I try my best not to touch any circuitry. I've never had a problem with stability or ruining any of the electronics.

As for the dust, my only concern is if it builds up on the fans or CPU heatsink. Dust on the fans can make them slightly unbalanced which can cause them to be a little louder. Dust build up in the CPU heatsink fins can increase temps. But both of these are extremely easy to clean with a vacuum cleaner. If you don't mind making a mess, I guess an even safer method is blowing air with one of those air cans.

tay · Post by **tay** » Thu Oct 07, 2004 10:11 pm

I'm too lazy to bother with filters. Speaking of which your links dont work for me anymore bluefront. Do I have to sign in somehow? I want to see how your filters are done even though I've seen the ahanix floor one before.

Katanaman, your impressive builds were some of the first ones I saw on SPCR and I have been here since. Just thought I'd let you know.

Bluefront · Post by **Bluefront** » Fri Oct 08, 2004 3:43 am

Lawn-mower filter

Rear filter/exhaust duct combo

Front Nissan in-cabin filter

Black Knight with bottom filter

Current Black Knight/Prescott setup

D-Box with two intake filters

Rear intake filter

DrCR · Post by **DrCR** » Fri Oct 08, 2004 6:26 pm

Front Nissan in-cabin filter

Pic 1 & 3. How quiet is that thin "card slot blower"? What voltages are you running at, and are you sucking in or blowing out? Why did you not use one in your new setup? To loud or just not needed?

Current Black Knight/Prescott setup

Furnace filter right? How did you make than angled, clear duct? Also, pic#87, why did you mount your HD upside down? Where did you get that prestofelt from? Just a local fabric or crafts store?

I'm sure you already posted this here so a simple link to another thread would be just fine.

Thanks,

DrCR

__________

Katana Man · Post by **Katana Man** » Fri Oct 08, 2004 6:36 pm

Please stay on the topic. This is not a filter thread. If you want to talk about filters, you can find Bluefront's filter threads here.

mathias · Post by **mathias** » Sat Oct 09, 2004 7:53 pm

I find that vacuumig alone does not work nearly as well as also using a blow dryer. Seems especially good at getting some of the dust in a PSU out. Compressed air cans seem rather expensive, but if they work as well or even better than a hair dryer, I can see why they're popular.

Straker · Post by **Straker** » Sun Oct 10, 2004 1:28 pm

yeah. vacuuming is pretty weak and canned air gets expensive... i just take components outside, blow all the dust off (no way to vacuum between dimms/heatsink fins etc anyways) then use q-tips and alcohol after.

Katana Man · Post by **Katana Man** » Sun Oct 10, 2004 2:21 pm

My beige LX-6A19 project is complete.

It was an enjoyable 4 hours of modding. I was smiling the whole time I was modding it, thinking about what my father's reaction might be when I gave it to him. He did not know he was getting a new case and upgraded computer. He thought I was coming over to help him format his computer. He was very grateful for this new case and computer, and he almost got a little choked up when I turned it on the first time. It is night and day compared to his old computer.

This has the usual mods to it:
1. Front bezel modified with modders mesh.
2. Front and rear case grills removed (tin snips)
3. Plastic fan holder removed.
4. New fan holes drilled.
5. Two Globe 120mm fans mounted with EAR fan isolators.
6. Fortron FSP-350PN w/ 120mm installed, fan grill removed.
7. Enermax 6 fan controller installed to control the fans.

Edward Ng · Post by **Edward Ng** » Sun Oct 10, 2004 2:39 pm

Now that is a truly wonderful SPCR success story.

Congratz!!!

datapappan · Post by **datapappan** » Wed Nov 10, 2004 2:12 pm

I also did some extensive testing regarding my (cardboard) CPU duct, and the amazing result was that ducting made things worse!

The duct was a rectangular box, guiding air from the back grille to the CPU fan top. Then took temperature readings with and without duct, resulting in:

CPU temp:
Duct +55 C/+67 C (Idle/Load)
No duct +49 C/+61 C

Ambient temp +21 C

Case temp:
Duct +30 C
No duct +32 C

Calculating backwards gives me that air flow w/o duct was 1,5 times the flow w duct, thus making up for the lower temperature gap available (67-21=46 deg ducted vs. 61-32=29 deg w/o duct).

Next action: dremel!

/ datapappan

Katana Man · Post by **Katana Man** » Wed Nov 10, 2004 2:29 pm

Atta boy! Get that dremmel fired up! Then add all 120mm fans everywhere like this:

(Note, I still have to remove the finger guard from this PSU.)

gregzeng · Post by **gregzeng** » Sat Dec 25, 2004 5:01 pm

Katana Man wrote:I've built hundreds of computers, and I've come to the conclusion, that using filters will keep the computer a little cleaner on the inside, but causes them to be louder. This is because you have to run the fans much faster to compensate for the poor air flow.
<SNIP> ....

Very good thread. My niece puts her computer under her bed, which is next to her study-desk.

Inside it gets long & short hair, cotton particles, car hair, skin discards, etc.

Ok. But the mess regulary clogs the CPU-cooler fins. What do do now?

It's worse for notebook computers!

The other way for "open"cooling - REMOVE the side walls of the case. What do you & others think? I keep my tower unit locked in a wooden cabinet, with air venting via duct outside of the cabinet.

Katana Man · Post by **Katana Man** » Sun Dec 26, 2004 10:12 pm

In my experience with the low air resistance, low fan speed, low noise technique, it worked best with the side cover on. This directs the air flow properly.

I don't think you'll be able to adopt this technique fully, but you can do a lot of it. In your situation, it sounds like you'll need to use a filter in front.

gregzeng · Post by **gregzeng** » Mon Dec 27, 2004 2:33 am

Katana Man wrote:In my experience with the low air resistance, low fan speed, low noise technique, it worked best with the side cover on. This directs the air flow properly.

I don't think you'll be able to adopt this technique fully, but you can do a lot of it. In your situation, it sounds like you'll need to use a filter in front.

In the case of my niece, who puts her computer under her bed ...

Reading other posts ... http://forums.silentpcreview.com/viewto ... 7b6ac12301

"Posted: Tue Nov 02, 2004 6:38 pm Post subject: breathing vs. streaming"
... I'm thinking putting a car-type filter inside the case, and a largish, slow moving fan, PUSHING (with a +ve case-pressure) clean air into the case.

If I switch off the PSU fan, and have the only air-outlet of the case from the PSU case at the other end of the filter-fan addition, will this be enough?

Of course I will leave the CPU FAN/ HEAT-SINK OPERATING NORMALLY, & the usual software alarm/ cut-0ff software operating quietly in the background. BTW: it's a P4, with the usual inbuilt CPU-overheating protection.

What does everyone think?

NigthStalker · Post by **NigthStalker** » Sun Jan 09, 2005 2:04 pm

i think that if most of the people don't cut out the case grills it's because it also means removing the motheboard so that no metal particles get caught up in the moto and burns it, and in my case removing the moto is a pain in the ass, so if you have any ideas on how cutting out the grills ( rear especially ) , tell me , you'd help me out.

gregzeng · Post by **gregzeng** » Mon Jan 10, 2005 6:26 pm

NigthStalker wrote:i think that if most of the people don't cut out the case grills it's because it also means removing the motheboard so that no metal particles get caught up in the moto and burns it, and in my case removing the moto is a pain in the ass, so if you have any ideas on how cutting out the grills ( rear especially ) , tell me , you'd help me out.

The case "grill" is really thin aluminium "strips" that can be easily snipped with the same side-cutters that you use for cutting thin electrical cables, such as household AC power cables.

The side-cutter's head can just fit into the holes. Press hard - and there are no metal fragments. The edges are rough & twisted, so use a long-nose pliers to press them flat & out of the way.

It matters not to me that it looks untidy, because I then put an air-filter over it, to hide the "ugly" hole from public view. With careful control of the long-nose pliers, you can make "gripping-extensions" that will better grip onto your air filter.

To attach the air filter, use hot-melt plastic from your hot-melt glue gun (or silicon rubber, or masking tape). If the filter needs cleaning/ replacing, use brute force to remove it from the case. The brute force needed will not damage anything.

Hope that helps.

ronrem · Post by **ronrem** » Thu Jan 27, 2005 12:27 am

V-Tech has cases that have a lot of area perforated and lined with filter material-incloding most of the door and a lot of the top. a couple of low speed exhaust fans,rear or bottom could provide outflow-without filter or other obstruction. There would be so much incoming air the filters would be no issue. However,without mods,the case would not be much barrier to what sound is created inside,so we are working on an offset noise barrier panel,a solid panel of wood with dense foam on the inner,leaving space for air to flow around it but blocking direct line sound waves. For this rig,having quiet stuff inside will be pretty important but ample clean air won't be a problem

Edward Ng · Post by **Edward Ng** » Thu Jan 27, 2005 3:32 am

ronrem wrote:...so we are working on...

ronrem, just for the record, do you work for V-Tech?

-Ed

ronrem · Post by **ronrem** » Fri Feb 11, 2005 1:25 am

Don't work for V Tech or any puter related outfit but am helping someone put togather a rig to mainly be used for music/audio-hunting for cases I originally was thinking of a case with minimal openings and internal damping but I saw one of these and wondered if a much different approach could work.

fastturtle · Post by **fastturtle** » Fri May 20, 2005 7:22 am

Thanks for the info Katana Man.

I guess I will now have to remove the fingerguard from my cpu fan as I never thought about its effect on air flow.

As to the modders mesh, have you ever tried fireplace screen mesh? I've got some of that laying about from another project and was wondering how it effects airflow.

Pendu · Post by **Pendu** » Mon Aug 08, 2005 4:15 am

sthayashi wrote:
Katana Man wrote:If the dust is heavy on the heat sink fins or elsewhere, I'll use a portable vacuum cleaner and have it resolved in a few minutes. I might vacuum a computer once, maybe twice per year.
Question: Are you're concerned at all about static build up and discharge with a vacuum cleaner (even a portable one)?

You can earth the long plastic tube quite easily just rung a wire with both ends stripped and then tape one side to the pc case and the other to the tube.

Low air resistance, low fan speed, low noise technique

Low air resistance, low fan speed, low noise technique

I second what's said on grilles

Re: Low air resistance, low fan speed, low noise technique

Ideas on cutting out the grills