SPCR

All-in-all, very well done.

Just one quibble:

Are the SLM readings are really that useful? The subjective descriptions of the sound levels are well done, so I'd be tempted to just go with those instead. Why clutter it up it w/readings that contradict what your ears actually heard?

*goes to buy his own planer*

Nice case. I especially like the ghetto rig for the PSU. I didn't see any fans mentioned for the intakes on the bottom of the case, though, nor any filters. I would think with the intake ports ~2 inches away from the carpet and no filter the thing would suck up dust like there's no tomorrow. Were there some preventative techniques that I just missed?

Green Shoes wrote:*goes to buy his own planer*

Nice case. I especially like the ghetto rig for the PSU. I didn't see any fans mentioned for the intakes on the bottom of the case, though, nor any filters. I would think with the intake ports ~2 inches away from the carpet and no filter the thing would suck up dust like there's no tomorrow. Were there some preventative techniques that I just missed?

I've found that on my really low airflow cases filters really aren't necissary. The amount of dust that accumulates on your gear is directly poportional to the amount of air moving through the case. With only a 120mm Nexus@7v, dust shouldn't be much of an issue. Also, I believe that the restriction on the intake that a filter causes is death to a case with such low pressure though the fan.

A great case, and a good review. I partly agree with rusty on the SPL measurements, I would have preferred "I can measure down to 30dBA, and this system is below that"...good enough

A really nice case, I like it a lot.

Well I'm planning to build my own case. Not a wooden one, probably aluminium but the cooling concept with psu at the bottom will be the same. Hopefully I will get it down in the next months.

I don't see that the SPL readings contradict what my ears heard. I agree that the extrapolations are pretty tenuous, but I included them because they suggest that the case is not just below 30dBA, but probably closer to 20dBA. That's a significant difference. I will concede that the section could have been abbreviated to a substantial extent without any great loss.

There's no intake fan or filter. So far dust doesn't seem to be an issue. If it becomes one, then I'll look into adding a filter.

Perhaps I should point out that I'm Doug?

Doug,

Nice job. I know that most audio speakers use MDF due to its acoustically "dead" properties. Did you consider MDF as an option?

hm. I wonder if something like mass loaded vinyl from a company like www.soundproofing.org would be a much better acoustic solution.

that hd is a wd 80 gig. I think they make more noise than almost any modern hd I have witnessed (besides a Fireball, but that's even older).

www.microcenter.com has Nidec motors in about 1/2 of their stock. 160 gigs is normal. this will, if suspended from head movement thumping, make it silent in that case.

If you read the design thread (there's a link in the last line of the article), there's lots of discussion regarding material, including suggestions of mdf. A lot of really high-end speakers actually use 13-ply birch. Both that and mdf would probably have been acoustically superior materials, but they both have a critical failing - they wouldn't have matched my desk.

Very nice job

brilliant. i really think this deserves some sort of award for ingenuitive design.

personally and practically (aka: boring); i would rather spend $120 on a water cooling setup with homemade blocks for cpu, northbridge, and vid card if necessary; no case fans and a lot of venting; but your system is gorgeous and it's really nice to see some much DIY ingenuity.

Nice job - reminds me of some speaker cabinets I built long ago.

You (and the site) concentrate on acoustic noise.

I was wondering about other types of noise such as RF

Metal cases are reasonable barriers to RF in the frequencies that our computers generate, but they do 'leak' around openings such as unscreened fan cutouts, rear panel openings w/o the mobo's panel installed, etc.

If you hold a radio near a PC and scan the AM bands you can pick up some interference. (BTW, in the 'good old days' of 4.77 MHz Z80 systems this was a good way to tell if you system was completely dead if you just had problems with your 24 x 80 character video board)

I don't know how far this stuff radiates or what the spectral content is, but we, as the sources of this stuff, are responsible for it. I seriously doubt that the FCC will mess with people building cases but scenarios where RF coming from an unshielded PC interferes with important or critical communications (alarms, for example) do exist.

Let's be careful out there!

ss

sixscrews wrote:... scenarios where RF coming from an unshielded PC interferes with important or critical communications (alarms, for example) do exist.

They have to be pretty rare. Also, Doug did discuss EMI in some detail in his article and found no serious issues.

Spinning the fans up to 12V results in a substantial hum, substantial enough that readings at 1m became possible: 31 dBA front, 33 dBA side, and 35 dBA rear. This is due to the fact that the right side door begins resonating as the Nexus is brought near to full speed. I had thought my foam block/elastic strap mounting technique provided good isolation, but apparently it doesn't, since the resonance drops off if the fan is pulled away from the foam. Since my temperatures are fine with the fans spinning slower, this isn't much of an issue, but it's clearly something I'll have to deal with if I should ever need a lot more airflow for some upgraded components in the future.

Yeah, that "foam" (pic link)looks like it's the type what is way too stiff to be good for such a purpose. Still though, if your comp is quiet enough for you now, there's no reason to use some other foam unless you need to crank up your Nexus to higher CFM levels.

Nice wood work btw.

DrCR

__________

To be fair, I only tested for EMI in the AM band, the 2.4GHz of my cordless, and whatever frequency cell phones work at. There's plenty of other frequencies that could cause issues. However, it should be noted that all those cases with big plexiglass windows provide no more shielding than mine, and no one goes on about EMI to them, nor are there frequent reports of trouble arising from them. I'm not going to worry about the issue until someone can provide me with actual evidence that I should.

Gorsnak wrote: it should be noted that all those cases with big plexiglass windows provide no more shielding than mine

Good point. Half of the rigs I use are run 'cover off' anyway as they see a lot of different hardware. Never had an issue it with myself.

Sorry for missing your mention of EMI in the article - mea culpa.

Yeah, you are right about not having problems with EMI at present with our lowrider style (hood off) or windowed rigs. I don't have problems at present, either, although I did spend a lot of time a few years ago tracking down some funny stuff in a microvolt-range data acquisition system. That turned out to be in part due to poorly shielded PCs, Ethernet cables and other electronic junk that we didn't think about the first time around (or the second of the third...).

As we get more connected via RF there is a potential for these problems to crop up. Most of our short-range systems use transmitters that are relatively powerful for what they are doing (yeah, WiFi doesn't seem to go very far and more power would help, but it is intended for short range and you really don't want your signal going clear across town, do you?) but there are a lot of nice applications that could work with very, very low power/short range transmitters - implants, for example.

I don't mean to be chicken little here - we don't have a problem most of the time - but just because we can't hear or see it doesn't mean it's not there, and RFI can be pretty insidious, causing intermittent problems and potentially affecting people other than the system builder.

Finally, building in RFI shielding and getting FCC certification is part of the cost of doing business for people who want to sell into the US market, with equivalent stuff in the EU and elsewhere. Ignoring that is one of the nice things about DIY, but the FCC still could plant its boot on you if there really is a problem and that would really spoil the party.

ss

sixscrews wrote:but the FCC still could plant its boot on you if there really is a problem and that would really spoil the party.

Actually, I'm pretty sure the FCC doesn't have jurisdiction outside the US, so I'm not real worried.

I'm sure there's a nice, bi-lingual, Canadian authority that would love to help you with your problems - I just don't know it's name so I didn't mention it. But I bet they wear boots, too.

ss

Doug, what a beautiful case!

Did you find that wood resonates more than sheet metal of standard cases? How does your case compare to the thick polyurethane cases out there? And do you think one might get the best of both worlds by wrapping a normal metal case with, say, a lot of foam?

Wood and steel resonate...well...differently. There's a reason that most musical instruments that use a resonant chamber to amplify themselves (stringed instruments, predominantly) are made from wood. Of course, the thicker wood is, the less it's going to make like a violin. I've no experience with polyurethane cases, so I can't comment on that.

If you want to wrap a metal case in something, be my guest, but you'll run into issues allowing space for air intake and access to optical drives, switches, and i/o jacks. You won't be able to replicate my bottom intake/rear exhaust thing with any case I know of with the possible exception of that Arctic Cooling Silentium thing, and sound will escape through the gaps you are forced to leave.

The way I see it, there's basically two features of my case that make it work. The first is that the front, top, and sides are pretty much sealed up tight. Sound can only escape out the bottom and the back, and I have sound absorbing (carpet and an acoustic panel) in both directions. Second, the case is heavy enough that sound doesn't travel straight through the sides. Sound blocking is to a large extent a function of mass, and there's a lot more heft to my case than a typical metal one.

Enlightening. I lack the skill, time, and courage to make one myself, but it's inspiring to see the creativity and workmanship of other SPCR people. I had no idea pine could look so good!

Great job, very nice and smart!

I was thinking about making something similar for my HTPC, but not tower.
Now, I have a few ideas about little improvements on noise, please take a look if you have a few minutes..

1. I was thinking about putting something like egg box inside case (like this here: http://www.solwayfeeders.com/images/lar ... ternet.jpg )
It should stop the noise, and keep it inside case. Am I right? (you are the expert)

2. Your motherboard is attached to the case, you said you don't have idea how to make it different. My case won't be tower, so MB doesn't have to be tight with case, I was planning putting some wood sticks, then screw mb into those sticks, and put some isolation between sticks and case.

3. Is there a way to isolate screws somehow?

Thank you! Once again, great job!

the material used as well as the shape is pretty critical. Perhaps you can pack the eggbox with some sound-deadening material.

That egg box cardboard isn't going to stop any noise. There's just no significant mass to it.

IMHO, there's little/no point to isolating the motherboard from the case. Isolating the CPU fan makes sense. But leaving the CPU fan hardmounted while isolating the motherboard merely turns the motherboard into a sounding board rather than the entire case.

does it need mass if it absorbs sound and is shaped to make multiple reflections (anechoic chamber type shapes) ?

The wavelengths of anything but the highest frequency noises are too big for a home computer to acheive many reflections. Sound will ignore spikey corner shapes smaller than the wavelength.

Since you can't really get all that many reflections, you really do need sheer mass to absorb as much noise as you can from the few reflections you get.

Hey who necroed my article thread?

Isaac is entirely correct. There simply isn't enough room inside a PC case to do much about anything other than high frequencies. Mass is the way to go if you're trying to contain noise.

Re: motherboard isolation. I tried some soft grommets and the like, and it had precious little impact. It's just so much easier to isolate the cpu fan that there's no point in even trying.

lead flashing?