[Czranito]

Hi,

I want/wanted to build a completely passively cooled HTPC. However, I'd have to sacrifice too much performance, so I'm wondering

-Which noise level is already inaudible ?
-How do the noise levels accumulate ? Are, for example, three 20db fans as noisy as one 60db ?
-When a fan is sold as, let's say, 25db, is it a minimum or maximum level ?
-How good/quiet are stock fans nowadays ?

Thanks

Z.

[DigiAl]

Suppose it depends if the fan is going be controlled by your motherboard or always on full.

You can get cables that reduce the voltage going to the fan, therefore the fan will run slower & quieter, or the motherboard can do this for you via its BIOS settings.

Also fan noise can be different dependant on the case and fittings used.

I found my stock CPU heatsink's fan was loud so remember to get a good one.

[GortWillSaveUs]

This really depends on what CPU/MOBO combo you're looking to buy.
I use the Scythe BIG SHURIKEN 2 Rev B. 5-Heatpipe Universal Low Profile CPU Cooler (SCBSK-2100) with no case fans,..and this bad boy does an awesome job all by itself. I have an A6-Build as my main HTPC with this cooler. There is no sound,..none.

[DigiAl]

indeed, i got the same and agree it does a good job.

Also worth considering is using SSD rather than normal hard drives as they produce lot less heat and therefore require less or no fan.

[Dougie Fresh]

Noise is so subjective, it's hard to say without some experimenting. A lot depends on the distance you sit from the HTPC, your environment (cabinet, rugs, room, etc.) even the content you watch (quiet music vs. exploding bass).

I've found the Intel stock cooler to be decent but the AMD stock cooler to be too loud for my tastes. For HTPC, since it's 10'+ away, I don't notice the fans as much as a desktop PC that sits 3' away.

Generally, the larger the fan, the slower it can run to move the same amount of air. I have not found a fan 60mm or smaller that I consider quiet that actually moves any air.

If you want quiet, then be prepared to allow your system to run "warm" not "cool" or "hot". It's a balance/compromise you're after -- not too noisy, not too hot.

[twelvebore]

All you want to know about quiet computing can be found here:

http://www.silentpcreview.com/

Your questions don't really have hard-and-fast answers, and at the end of the day there's no substitute for personal experiementation.

-Which noise level is already inaudible ?

Depends on many factors, eg. where you live (ie. ambient noise), how close you are to your computer, your age/hearing, and so on. It can depend on the nature of the noise too, for example a white-noise signal might audible but not really noticeable, whereas something tonal or chattery would be far more irritating.

There's personal things too - people vary in their tolerance/sensitivity to noise.

-How do the noise levels accumulate ? Are, for example, three 20db fans as noisy as one 60db ?

Two 20dB fans would be 23dB.

-When a fan is sold as, let's say, 25db, is it a minimum or maximum level ?

First rule of buying fans: all manufacturers noise specs are nonsense. Ignore them.

-How good/quiet are stock fans nowadays ?

Better than they were, and they can be acceptable under certain circumstances.

[SSDD]

Great post twelvebore. Definitely check out silentpcreview.com to get your bearing on quiet computing.

Just to add to the inaudible question- another thing is the type of noise that bothers you. For some people it is the whoosh of the air (which can be caused by filters, grills, etc and only really fixed by flow rate rather than fan selection), others can dislike the sound of the type of bearing the fan uses, and so on. Check out the recordings that SPCR does for the different fans to get a better idea.

[Balinus]

It also depends on your age!

Personally, I have 1x80mm case fan and the stock AMD cooler and both runs at around 900RPM and I don't hear them! 33 yr old, open cabinet and about 8 feet from the HTPC. Both fans are controlled by the motherboard through PWM.

If your motherboard allows you to plug PWM fans, go for it. Easy to tweak with the BIOS or Speedfan. My system runs about 45 C, so it doesn't run "hot" imho.

[GortWillSaveUs]

Noise is so subjective, it's hard to say without some experimenting. A lot depends on the distance you sit from the HTPC, your environment (cabinet, rugs, room, etc.) even the content you watch (quiet music vs. exploding bass).

Totally agree! How about noise from the refrigerator, traffic outside, the dog barking, the kids,......you get the point.
Most of these things, your mind will filter them out and you won't even notice them anymore.
Not all of us can afford a home theater room that keeps out those noises.

[Mallet21]

I tend to focus more on the RPM's than the listed dB.....the lower the RPM's the quieter the fan (obviously though at a lower RPM it is not moving as much air). Like Balinus above, my CPU fan (stock AMD cooler) is at 1200 rpms and my exhaust fan (stock Antec fan) is at 800rpms and I cannot hear them unless I put my ear right up next to the case.

[teaguecl]

-How do the noise levels accumulate ? Are, for example, three 20db fans as noisy as one 60db ?

Two 20dB fans would be 23dB.

This is true, but remember that 23dB is twice as loud as 20dB! So yes, the fan noise is cumulative and 3 20dB fans are three times as loud as a single one (26dB total). Decibels are not linear - a double in loudness is a increase of 3dB. Half the noise is 3dB lower.

[Czranito]

Also worth considering is using SSD rather than normal hard drives as they produce lot less heat and therefore require less or no fan.

Yep, that's the plan, two SSDs in RAID 0.

Noise is so subjective, it's hard to say without some experimenting. A lot depends on the distance you sit from the HTPC, your environment (cabinet, rugs, room, etc.) even the content you watch (quiet music vs. exploding bass).

I think I'll usually sit like half a meter away, wooden floor. But since I'm going to use it as a regular computer as well, it might play no sound at all for most of the time.

Your questions don't really have hard-and-fast answers, and at the end of the day there's no substitute for personal experiementation.

Experimantation would sure help, but I can't really buy 10 fans and return the 9 I don't like, can I ?

-When a fan is sold as, let's say, 25db, is it a minimum or maximum level ?

First rule of buying fans: all manufacturers noise specs are nonsense. Ignore them.

Those scoundrels ! So based on what should I pick something to buy then ? Is it just the lowest RPM as Mallet21 said ? Are at least the air flow specs legit ?

Check out the recordings that SPCR does for the different fans to get a better idea.

I didn't know someone recorded fan sounds, cool !

-How do the noise levels accumulate ? Are, for example, three 20db fans as noisy as one 60db ?

Two 20dB fans would be 23dB.

This is true, but remember that 23dB is twice as loud as 20dB! So yes, the fan noise is cumulative and 3 20dB fans are three times as loud as a single one (26dB total). Decibels are not linear - a double in loudness is a increase of 3dB. Half the noise is 3dB lower.

Wow, I had no idea it's not linear, you probably saved me from a shitty purchase

I'm 28, I don't hear that bad I hope, except of after a gig

As for motherboard, I am deciding between

ASUS Maximus IV Gene-Z/GEN3 http://www.newegg.com/Product/Product.as...6813131806

and

MSI Z77MA-G45 http://www.newegg.com/Product/Product.as...0Z77MA-G45

They both have what I want - can they control fan speeds without an additional hardware ?

CPU should be i3-2120T or i5-2390t or i5-2500t - But I can't find the last two anywhere. A 35W CPU should be fine with just passive cooling, right ?