Deadening aluminum cases?

Enclosures and acoustic damping to help quiet them.

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Sunfox
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Deadening aluminum cases?

Post by Sunfox » Thu Nov 02, 2006 6:13 am

I'm going to be building a new system soon, and I was considering switching from my original P180 (complete with super-warped front door) and going for something a bit more extravagant, like an aluminum Lian Li.

Of course, in my research I've heard that there's a bit of a vibration transmission issue with aluminum, so I wanted to hear about any of you SPCRers that have successfully soundproofed one of these types of cases to "acceptable" levels, and what it involved.

What sort of noises are these cases prone to fail to contain? Does the thickness of the aluminum help at all with high frequency issues? Is it mostly low frequency vibration? Would something like lining the interior with Dynamat Extreme help? What else?

Thoughts/suggestions appreciated!

RAFH
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Post by RAFH » Thu Nov 02, 2006 11:32 am

Pretty much anything that will add mass will help.

Also measures that will break up vibrating membranes into random elements will help. This is sort of like when you clap your hands in front of a large smooth wall, you get a sharp report, whereas if its a very rough surface with lots of different angles, shapes and sizes you will get a soft hush type of report. The one is like a mirror which reflects a perfect image, the other is just the opposite, dispersing and fracturing the image. So adding some stiff structural elements will break up the surface that is reflecting or transmitting the sound image. Gluing on some ribs of random shape and size.
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nici
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Post by nici » Fri Nov 03, 2006 5:01 am

Dynamat, or any other heavy mass damping, will reduce/eliminate vibration. Foam makes the noise smoother, and reduces it some.

I am not sure if anyone has succesfully tried the "Gluing on some ribs of random shape and size" method in a computer case around here. Unless the material is sound absorbing, it probably wont work very well inside a small box like a computer case.

Sunfox
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Post by Sunfox » Fri Nov 03, 2006 6:27 am

...Any thoughts on whether it's even worthwhile to attempt something like this? Having never used an "all aluminum" case I don't know exactly how much louder they are to start with...

nici
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Post by nici » Fri Nov 03, 2006 7:08 am

If you use quiet components to start with it's not a huge difference. The problem is vibrating components and thin alu cases, Lian Lis are pretty sturdy, and after adding damping to any au case it will be at least equal to a steel case of similar quality. There is also crappy and tinny steel cases..

My system would not be any quieter in a steel case.

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Post by RAFH » Fri Nov 03, 2006 8:31 am

There's no question that starting with quiet components will make more difference than almost any dampening you might do to a case. As noted, there's usually not a lot of room to do much.

Fans are usually the biggest noise source, start with quiet fans. Remember two 20 db fans pushing 30 cfm each will quieter than one 25 db fan pushing 60 cfm. Sound is generally not additive unless the sources are synched though you could get an annoying warble effect where they overlap.

Bigger fans usually do more work with less noise.

Oversized fans allow you to back off on the speed and drop noise levels significantly.

The other major source is HDD seeking. A good suspension system will help with that, something to keep the vibrations of the drive out of the frame. Usually silicon grommets will do wonders. For extreme cases, rubberband suspension like Antec offers should do the trick. Plus the more interruptions in the sound path, whether in the metal or through the air, the better.

Another good strategy is making sure what sound gets produced doesn't come your way, at least no directly. Most of the time, users are concerned with what comes out the front. Its also important to address what bounces off the wall behind. A good sound absorbing and dispersing surface behind the computer, where most of the sound energy exits the case, will help prevent that noise from bouncing back toward the front. Adding a baffle of some sort back there would also help a lot.

I do go back to the matter of mass, look for thicker panels or panels that are built up of layers. Adding your own layers is also helpful, something dense with a random texture will probably work the best.
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Poodle
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Post by Poodle » Sun Nov 19, 2006 7:32 pm

The best thing to use for Al cases is 4mm thick BITUMEN. I think it's a petroleum product much like tarmac (asphalt) so it's black and a bit like clay and is really HIGH DENSITY. It's used to quiet the engine room in cars and in the cabin for those that have high wattage sound system. So you get at car spare parts shops in big sheets with a thin plastic film on the front side adding integrity to the material and glue on the back with the orange film protecting the clue. Really easy to work with.

Shown : http://www.mds.se/?artnr=480005

For Swedes: It's not that expensive at the right place. Mekonomen charges 41kr for the same stuff and amount of material.

It's really thick and heavy. There's nothing better, I've tried everything. I've used it in both Lian Li and CM cases. It also cheap. Stay away from the textile-ish stuff that they also have at those shops. It's not good at all + that i releases dust that gets stuck in fans.
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nici
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Post by nici » Mon Nov 20, 2006 1:55 am

Then you have not tried butyl based products like Dynamat Extreme or RAAMmat.. Better in every way compared to bitumen, but several times more expensive, but for cars it's DEFINATELY worth it. I had bitumen in my car, but it started cracking and the glue didnt hold well after two years. not good. The last place i would put bitumen is in the engine room of a car, it may work for a while but the heat will eventually make it fall off, it works for horisontal mounting like the floor, but not the roof or engine compartment or doors, it will eventually fall off or melt and then fall off. Butyl based stuff does not have that problem. That being said, i have 4mm bitumen in my current case because i had some over from other things.

Have a look here

roadie
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Post by roadie » Mon Nov 20, 2006 3:07 am

I think the most important thing is to start with a case made out of thick aluminium. My case is well built internally but the side panels are made out of very thin aluminium and initially this cause a lot of resonance from fans and hard drives. I bought some Acoustipack and applied it everywhere I could, which helped but the case is still not as quiet as I would like.

I would very much like a black P180.
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Post by Bluefront » Mon Nov 20, 2006 3:15 am

If you start out with a sturdy aluminum case, there should be no extra noise problem due to the aluminum. Something like 2mm thick panels should do it.

My AMS case did not require any Dynamat-like stuff. The problem with that sort of material.....it's almost permanent. You can't remove it without a big hassle. If you first line the area with a high-quality duct tape, then apply the Dynamat, it can be removed without too much trouble..
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nici
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Post by nici » Mon Nov 20, 2006 4:08 am

I still wonder why one would need to remove the stuff..
If you start out with a sturdy aluminum case, there should be no extra noise problem due to the aluminum.
I agree, the difference to a steel case is non-existant. But i apply mass damping even to steel cases, and foam to absorb sound(works really well for HF whine).. Also thought about lead sheets as it acts as a barrier wich mass damping and foam does not.

Felger Carbon
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Post by Felger Carbon » Mon Nov 20, 2006 9:18 am

nici wrote:Also thought about lead sheets...
Shame on you! The RoHS folk won't like you at all! At least butyl isn't toxic, and it doesn't produce low-IQ children. :lol:

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Post by nici » Mon Nov 20, 2006 4:09 pm

As long as i properly recycle them, it wont harm anything or anyone, and i did say i have only thought about buying some :wink:

Butyl rubber lowers the resonant frequency of the piece, but does not block sound that much. Lead blocks sound, and foam absorbs and diffuses it. :P

kater
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Post by kater » Mon Nov 20, 2006 11:05 pm

butyl rubber, lead, extra heavy sheets of dampeners etc...

my rig already weighs 15 kg, and that's not sli, no raid, 1 odd, no fancy extras, a minitower... imagine adding the stuff discussed here and i'll need a hoist

no, i don't take it to lan parties, i don't move twice a year but i do dabble with it at least weekly, changing innards, replacing parts, generally messing around, and i can already feel my deltoids and addutors grow :lol:

qdemn7
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Post by qdemn7 » Tue Nov 21, 2006 6:03 am

From my personal experience, the best stuff is Acoustipack It's expensive but well worth it.

nici
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Post by nici » Tue Nov 21, 2006 4:37 pm

Probably best of the ready made "computer dampeners", yes. I quite like it myself. But if you know your materials, you can do better with other stuff :) It wont be as easy or convenient as acoustipack, it's harder to find, and it's somewhat more difficult to get looking nice.

EdT
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Post by EdT » Thu Nov 23, 2006 8:41 pm

I have a KingWin ST-424S which is very simialr to the Lian-Li. Nice case, but alot of resonance from the sheet metal. Slowy, but surely I am removing and adressing each sound day by day or month by month. I used something very similar to the ultra expensive dampening mats, but it only costed me $2 to do my whole case with self sticking dense foam I found at the Dollarama. and that dampens quite alot of canning sounds. I just removed those plastic carbon fiber front cover ends which is only held on with two srews on the side and figured that cause alot of vibration between the plastic and the sheet meatal. I simply added a few drops of epoxy and the annoying vibrating sound went away.
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Post by TMM » Sat Dec 02, 2006 7:08 am

My server has a custom alu case, and i found the sidepanel to be resonating pretty badly. I've bolted a piece of wood across the inside of the panel and it doesn't resonate anymore ;)
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Post by HammerSandwich » Wed Dec 06, 2006 6:44 am

Glue McMaster-Carr item 54665T32 to the panels. The stuff's dense, dead, easy-to-cut and cheap.

Felger Carbon
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Post by Felger Carbon » Wed Dec 06, 2006 8:07 am

HammerSandwich wrote:Glue McMaster-Carr item 54665T32 to the panels. The stuff's dense, dead, easy-to-cut and cheap.
That stuff is 54" wide. Is it shipped rolled up, or in a large cardboard box? Also, it's not self-sticky, so the subject of what glues to use, and how to apply, comes up for the first-time user. At least Dynamat Extreme has no such problems.

I have moved from DE to the self-adhesive 1ftx1ft buna rubber on McMasters page 3328. The 3/32" is ~$6 for one sq ft, and is equivalent to about 1.5 layers of DE in weight and in dampening effect. Get the softest available (30 or 40 rating).

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Post by HammerSandwich » Wed Dec 13, 2006 7:56 am

Felger Carbon wrote: That stuff is 54" wide. Is it shipped rolled up, or in a large cardboard box? Also, it's not self-sticky, so the subject of what glues to use, and how to apply, comes up for the first-time user.
Rolled up - it's pretty flexible. I've had success with both rubber cement and 3M trim adhesive.

The buna rubber you use sounds like a good bet.

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Post by zepper » Sat Dec 16, 2006 2:47 pm

I use rope caulk (Mortite and FostKing are brand names in the states) to damp ringy panels on the cheap - I used to use it in the old audiophile days to damp and balance turntable platters. I just keep adding random length strings until it's dead enough. Not pretty but cheap.. And you could take some dense fabric like felt to stick to the inside of the caulk so you don't have to look at it. Clean the insides of the panels well with detergent in water, rinse, dry well and wipe down with high percent alcohol and the caulk wil stick indefinitely.

.bh.
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