Cooler Master 840 resonance noise

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Pegi

Limp Gawd
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May 31, 2005
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I had a computer built for me using the Cooler Master 840. The completed computer arrived via fedex and although the box was not damaged at all, it had apparently had a few jolts, as when I opened the case the hard drive was hanging by one plug and the sliding mechanism wheel on the hard drive had broken off, but we fixed that up.

Generally, the computer is beautifully silent, with just the whooshing sound of the air coming out of the top; really very quiet. And then out of nowhere a resonance noise will start up. Fan blades are not hitting anything, just a sort of echoing ratchety noise. If I mess around with the case; i.e., anything from pressing on the sides sometimes or moving it a little any which way, the noise will stop and it will be fine for another week or so before it might start again. The computer itself, by the way, works *wonderfully,* with no problems, hardware wise, whatsoever.

Basically, I'm asking is this case prone to resonance noise or did shipping damage something irreparably? Is this something that will get worse with time and should I return the computer? Or is there something a clever modder can suggest I do? I realize I'm a little vague in describing the noise, but I'm guessing if this is a particular problem with this case someone might understand what I'm describing. Would appreciate any thoughts.
 
Aluminum case, right?

Try putting the hard drive on a piece of foam. Also, soft mounting the fans might help.
 
Yes, it is an aluminum case. Are you suggesting aluminum cases are prone to these types of noises even in the best of circumstances...I shouldn't be so quick to blame damage caused during shipping?

We did put a piece of foam in between the two fans on top and will see if they helps in the future. Can you elaborate on soft mounting? I haven't been able to localize where the sound is coming from; you think it might be hard drive resonance? I have 2 hard drives; a solid state and a WD caviar.

Aw heck, I just touched the side of the darn thing and it started up with that whirring resonance sound again. And, again, by jockeying it around a bit, it stops. Does anyone with this case have this same problem?
 
Pegi said:
Yes, it is an aluminum case. Are you suggesting aluminum cases are prone to these types of noises even in the best of circumstances...I shouldn't be so quick to blame damage caused during shipping?

We did put a piece of foam in between the two fans on top and will see if they helps in the future. Can you elaborate on soft mounting? I haven't been able to localize where the sound is coming from; you think it might be hard drive resonance? I have 2 hard drives; a solid state and a WD caviar.

Aw heck, I just touched the side of the darn thing and it started up with that whirring resonance sound again. And, again, by jockeying it around a bit, it stops. Does anyone with this case have this same problem?
Click to expand...

You may need to "mass load" the side panels of the case. Oftentimes very minor vibration from fans or hard drives will case the entire case to resonate just a bit. You can use acoustic panels designed for cars, or some Acoustipack.

Here's the SPCR take on aluminum case reverberation: http://www.silentpcreview.com/article75-page2.html

"Soft mounting" a fan involves rubber grommets (or rubber "fan screws"), foam, or even velcro. All of the above don't use a steel screw, which transmits vibration from fan to case.

I doubt shipping damage has anything to do with it. Aluminum cases have always been prone to the types of noise you've described.
 
I have had my 840 since September, and I have heard no odd noises. However, when the fan on my HD 4850 spins up to 100%, things get loud.
 
Inbalanced fans can produce quite noticeable vibration and best solution to that is not having that vibration at all in the first place, that's one reason why easy to replace standard size fans are good.
But couple millimeters of bitumen is also good and cheap way.


JaYp146 said:
or some Acoustipack
Click to expand...
Current Acoustipack doesn't anymore have that dense bottom layer it had in SPCR's review so now it would require first applying bitumen mat for good damping of vibrations.

Actually screw is often included in soft mounting but it and drive must not touch anything else than rubber grommet which is between that drive "assembly" and HDD cage structure of the case or otherwise vibration has other routes to spread forward.
 
Thanks so much for the silentpc review. It's an eye opener. While I can't specifically localize the noise to an imbalanced fan or vibrations from hard drive or screws (or all of the above), I'm inclined to blame fan imbalance more than anything else. I must stress that the noise is *really* loud. You can hear it from the other end of the house. Yet, if one just moves the case just a teeny bit one way, all of a sudden it's gone, until you touch the case again and it returns. I feel very unsettled thinking that this is more than just average noise resonance. My previous case was a Cooler Master stacker and I've heard nothing remotely like this.

If I tried getting a bitumen mat, would I also need to get the Acoustipack...or would the mat alone be enough? Should I ask the computer builder for replacement top fans?

On second thought, I'm thinking the hard drive cages seemed to get a little warped in shipping. Will open the case up later today and see if I can't insulate that before doing anything else.
 
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It's not that unheard of for those big fans to cause that kind vibration of panels. (but also worth checking that HDD cage)
Current AcoustiPack is really designed just against airborne sound so it wouldn't help much to vibration.
 
When I opened her up, noted the 2 large fans on top were barely even screwed in, just flopping around. Tightened that up. For now, that seems to have been the main issue, I think. When I now touch the sides, it doesn't start off that horrendous churning noise. I'll just watch it for now and see how it goes before investigating insulating any further. I don't care so much about a *quiet* computer but I sure don't want a *noisy* one! Appreciate everyone's input very much as well as the Web site.
 
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