Question about a multiple fan setup

permabear86 · Post by **permabear86** » Sun Oct 03, 2010 9:48 am

Hey guys I am going to be building an air cooled system in a Lian Li PC-X1000 case with the intent of making it as close to silent as possible and overclocking the living crap out of it

. I am going to be replacing the 5 stock Lian Li fans with 5 Thermalright TY-140 fans as well as using a Thermalright Silver Arrow cooler which comes stock with 2 of the TY-140s. I will be cooling my GPU with an Arctic Cooling Accelero Xtreme Plus cooler which has 3 92mm fans onboard. The hard drives will be in Smart Drive enclosures suspended from elastic bands.

This means there will be 5 case fans, 2 cpu fans, 1 psu fan, and 3 fans on the GPU cooler. All fans will be 140mm with the exception of the 3 92mm gpu fans. Is it possible for this setup to be silent or at least very very quiet if I run all the 140mm fans between 500-800rpms and run the GPU fans very slowly as well?

Thanks so much in advance!

Edit: I should also add I may end up using a Thermalright Spitfire + VRM cooler for the GPU so I won't have to use any fans smaller than 140mm.

lodestar · Post by **lodestar** » Sun Oct 03, 2010 11:00 am

Although described as a 140mm fan the Thermalright TY-140 is an oversized 120mm fan, so it has 120mm fixing holes and as far as I know is not supplied with fixings to allow it to be fitted as a 140mm fan replacement.

permabear86 · Post by **permabear86** » Sun Oct 03, 2010 11:25 am

lodestar wrote:Although described as a 140mm fan the Thermalright TY-140 is an oversized 120mm fan, so it has 120mm fixing holes and as far as I know is not supplied with fixings to allow it to be fitted as a 140mm fan replacement.

I am going to get adapters from Noctua.

danimal · Post by **danimal** » Sun Oct 03, 2010 2:54 pm

i have that siver arrow cooler, it rocks, and i really like the fans... you could hook all of 'em up to the pwm cpu fan controller, although you'd probably have to build a custom power cable.

you won't need to replace the hdd/psu fan on the bottom, and it looks like the adapter probably wouldn't fit anyway... just undervolt the lian li fan.

sounds like a great build!

datapappan · Post by **datapappan** » Sun Oct 03, 2010 3:13 pm

It depends on what you deem as quiet. For starters, you have 12 fans, which will add 11 dB to the noise of only one fan, if they all ar run at the same speed. This then has to be added to your background noise, resulting in your audible noise level.

Example: background noise in my suburban house is 30 dB. If I want truly "silent", I have to cut noise from fans so that they add up to 31-32 dB (at 33 db the 3 dB change is clearly audible). This forces the fan noise down to just 27 dB, for the full setup (using decibel subtraction formula). Subtracting the 11 dB as per above brings you down to 16 dB, for a single fan. Revving down a bit should take you to that value - so yes, it can be silent.

If you are happy with higher noise, you can rev up the fans accordingly.

[Technical note: fan noise figures seem strange to me - Thermalright gives the figures 900rpm=19dB and 1300rpm=21dB. Noise usually changes with rpm as 50xLOG(rpm1/rpm2). The figures don't match with this. If noise is measured in a non-silent environment, i.e. with some background noise, they make more sense. Backtracking the figures above, ambient noise at testing would be 18.5 dB, and 900rpm=9.4 dB, fan only, and 1300rpm=17.4 dB. Adding noise levels adds up to the figures above. Taken like this, an rpm of 1210 should fit the bill, or 16dB that is).]

/d

permabear86 · Post by **permabear86** » Sun Oct 03, 2010 4:05 pm

datapappan wrote:It depends on what you deem as quiet. For starters, you have 12 fans, which will add 11 dB to the noise of only one fan, if they all ar run at the same speed. This then has to be added to your background noise, resulting in your audible noise level.

Example: background noise in my suburban house is 30 dB. If I want truly "silent", I have to cut noise from fans so that they add up to 31-32 dB (at 33 db the 3 dB change is clearly audible). This forces the fan noise down to just 27 dB, for the full setup (using decibel subtraction formula). Subtracting the 11 dB as per above brings you down to 16 dB, for a single fan. Revving down a bit should take you to that value - so yes, it can be silent.

If you are happy with higher noise, you can rev up the fans accordingly.

[Technical note: fan noise figures seem strange to me - Thermalright gives the figures 900rpm=19dB and 1300rpm=21dB. Noise usually changes with rpm as 50xLOG(rpm1/rpm2). The figures don't match with this. If noise is measured in a non-silent environment, i.e. with some background noise, they make more sense. Backtracking the figures above, ambient noise at testing would be 18.5 dB, and 900rpm=9.4 dB, fan only, and 1300rpm=17.4 dB. Adding noise levels adds up to the figures above. Taken like this, an rpm of 1210 should fit the bill, or 16dB that is).]

/d

Perfect! Thanks for the detailed response. Also regarding Thermalright's figures, I would take them with a grain of salt.

http://www.xbitlabs.com/articles/cooler ... html#sect0

Here is a review of the fan in Xbit's 140mm fan roundup. According to this review the fan is 31-33db from 0-~850 RPMs so I guess its effectively silent up until that point. I am not sure how they tested and whether or not it was accurate though.

danimal wrote:i have that siver arrow cooler, it rocks, and i really like the fans... you could hook all of 'em up to the pwm cpu fan controller, although you'd probably have to build a custom power cable.

you won't need to replace the hdd/psu fan on the bottom, and it looks like the adapter probably wouldn't fit anyway... just undervolt the lian li fan.

sounds like a great build!

I may just replace the psu/hdd fan so everything matches but you're right it is unnecessary. I don't need top notch airflow in that compartment. Thanks for pointing that out.

permabear86 · Post by **permabear86** » Mon Oct 04, 2010 12:56 pm

datapappan wrote:It depends on what you deem as quiet. For starters, you have 12 fans, which will add 11 dB to the noise of only one fan, if they all ar run at the same speed. This then has to be added to your background noise, resulting in your audible noise level.

I have a question for you. This is taken from the "Are 2 fans quieter than 1 blowing the same CFM?"

"I think it is safe to say that when you combine low speed fans, that +3dB rule gets moot because...

1) your hearing is not sensitive to that noise because it's mostly low freqs. Certainly you don't hear volume changes as linearly as in the midband. So you just can't hear the increased acoustic energy / SPL even though it's there.
2) the audibility may be borderline because it's at or near ambient level, so again, you can't hear it or not well.

BTW, AFAIK, low freq sensitivity in human hearing does not change much with age -- except maybe for those who really elderly or with abnormal hearing loss/damage. "

If this is true, does this mean that basically even though the dB go up with each additional fan, it is too low of a frequency for the human ear to pick up as long as they are spinning slow enough?