Dual 80mm or Single 120mm for Rad

flak said:
2x80mm = 12800 sq mm
1x120mm = 14400 sq mm
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the single 120mm will have more surface area and will likely push nearly the same air as the double 80mm fans while being quieter. if it fits go single 120mm.
 
unless you're still trying for quiet over cool, in which case the 2 x 80mm @ 7v will be quieter than a 120 @ 7v.
 
Thats not true ...

120mm Deltas 72.4CFM 34dB dB/CFM = 0.47
80mm Deltas 68.51CFM 48.5dB dB/CFM = 0.71

As you can see, the 120s push out 'nearly' the same amount of air (72.4 vs. 68.51) at more then 10dB less!!! The reason people go with 120mm's is due to the fact that they are quieter, they do this because the 120's run at a lower RPM (2100 vs. 4900!). Coincidentally the high powered 120mm Delta still runs quieter then the 80mm and it pushes 86.5CFM !! at 37.6dB. Conclusion, go with 120mm if you want quiet :)
 
PS forgot to mention, this is STILL the same when volt modded to 7v, comparitavely the 120m and 80mm's run at 12V each, so volt modding both to 7V would result in a propotional decrease in sound, but the ratio of dB/CFM would remain the same ... volt modding an 80mm to 7V would probably be quieter then a 120mm at 12V, but on the same token it wouldn't be much quieter, and the amount of CFM it pushes would be MUCH less then the 120mm :)
 
While 120mm fans are definitely quieter, I thought that higher RPMs were better when you were pulling air through a radiator. It creates higher pressure or the like. The 120mm moves more air when unrestricted, but when pulling through a radiator, I've read two smaller, higher RPM fans should perform better.

Thoughts?
 
HiTech-Hate said:
Thats not true ...

120mm Deltas 72.4CFM 34dB dB/CFM = 0.47
80mm Deltas 68.51CFM 48.5dB dB/CFM = 0.71

As you can see, the 120s push out 'nearly' the same amount of air (72.4 vs. 68.51) at more then 10dB less!!! The reason people go with 120mm's is due to the fact that they are quieter, they do this because the 120's run at a lower RPM (2100 vs. 4900!). Coincidentally the high powered 120mm Delta still runs quieter then the 80mm and it pushes 86.5CFM !! at 37.6dB. Conclusion, go with 120mm if you want quiet :)
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remember that dB is logarithmic. i don't think you can do the math like that.
 
sure you can, the logarithmic scale of dB refers to the percieved sound, im simply comparing the number of CFM's per dB, my math had nothing to do with the actual sound percieved.
 
HiTech-Hate said:
PS forgot to mention, this is STILL the same when volt modded to 7v, comparitavely the 120m and 80mm's run at 12V each, so volt modding both to 7V would result in a propotional decrease in sound, but the ratio of dB/CFM would remain the same ... volt modding an 80mm to 7V would probably be quieter then a 120mm at 12V, but on the same token it wouldn't be much quieter, and the amount of CFM it pushes would be MUCH less then the 120mm :)
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i will challenge you then to find me a 120mm fan that is quieter @ 7v than two 80mm panaflo "L" fans @ 7v. even better, find me a fan that is quieter @ 5v. if you can do this, i will be buying new fans. subjectively speaking though, i have not HEARD any 120mm fan, @ 7v that's quieter than the 80mm panaflo @ 7v. and believe me, i have gone through a lot of fans.
 
ever try one of those nexus real silent fans?

I think globe also makes a rather quiet 120mm fan.
 
i will challenge you then to find me a 120mm fan that is quieter @ 7v than two 80mm panaflo "L" fans @ 7v. even better, find me a fan that is quieter @ 5v. if you can do this, i will be buying new fans. subjectively speaking though, i have not HEARD any 120mm fan, @ 7v that's quieter than the 80mm panaflo @ 7v. and believe me, i have gone through a lot of fans.
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Heh, I wont deny that there are quieter 80mm fans, all I was trying to say is that these fans dont push nearly as much air as a proportionally loud 120mm would .. eg. the panaflo you speak of only pushes 24CFM. For 6dB more (which is still very quiet) you can have a 120mm that pushes 75CFM :) Its all a matter of personal tolerance, some people have this obsessive need to remove every single whisper of noise from their case (I argued with someone the other day who wanted to put a chipset block on simply because he was concerned that the chipset fan would be too loud in his wc loop ... ).

If you want absolute quiet, then go with the 80s, but understand that you are sacrificing signigant performance. Its also important to note (and I forgot to do this earlier) that the dB scale is logarithmic with respect to the POWER DELTA .. so in other words, an increase of 1dB doesnt equate to a doubling of sound .. it equates to a doubling of the change in power. You're best bet to actually understand how loud a certain dB is would be to scour the internet for wav's of the sound of some of the fans you're looking for, a bunch of companies have wavs on their site ... all of which escape me right now :)
 
HiTech-Hate said:
Heh, I wont deny that there are quieter 80mm fans, all I was trying to say is that these fans dont push nearly as much air as a proportionally loud 120mm would .. eg. the panaflo you speak of only pushes 24CFM. For 6dB more (which is still very quiet) you can have a 120mm that pushes 75CFM :) Its all a matter of personal tolerance, some people have this obsessive need to remove every single whisper of noise from their case (I argued with someone the other day who wanted to put a chipset block on simply because he was concerned that the chipset fan would be too loud in his wc loop ... ).

If you want absolute quiet, then go with the 80s, but understand that you are sacrificing signigant performance. Its also important to note (and I forgot to do this earlier) that the dB scale is logarithmic with respect to the POWER DELTA .. so in other words, an increase of 1dB doesnt equate to a doubling of sound .. it equates to a doubling of the change in power. You're best bet to actually understand how loud a certain dB is would be to scour the internet for wav's of the sound of some of the fans you're looking for, a bunch of companies have wavs on their site ... all of which escape me right now :)
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i agree 120 is much more efficient and silent soolution, while still keeping a worthy setup, 2 panaflos 80mm l at 7 volts are not what you want to install in a rad, sure it will be silent, but it wont cool the rad.
 
i don't disagree that the 120mm will push more air, all i was stating was that the 80's will be quieter than the 120 if your primary concern is silence. no it won't cool as well, but that's true of any system, air or water (higher cfm = cooler temps).

BUT there are things you can do to lower temps and keep it silent. i ran my 2.4p4 oc'd to 2.7 for about 3 months without any kind of radiator at all and temps climbed to around ~55 under load, and my res held approx 1.25 gallons of water. loop looked like this:

pump -> cpu -> gpu -> res -> pump

i added a radiator (heatercore, about 10x6x2) and ran it without any fans in the same loop. temps dropped to top out at ~43, which is significant and still no noise.

i can't comment on how well the dual 80 rad will perform with such low airflow but i can say for sure that it will be very quiet with the right fans. the 120 would be quiet with the right fan at the right voltage as well, but again you sacrifice airflow for noise. sacrificing airflow sacrifices temps as well, so that's the trade off.
 
Ever use iCute fans? I have some 80mms from them that push at least a good 40 CFM, but even at 12v they're almost inaudible. My case came with several of them.
 
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