2x80's > 1x120 ?
Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee
2x80's > 1x120 ?
OK, this is probably a stupid question, but would two 80mm fans be quieter than one 120mm fan blowing the same cfm?
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datapappan
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- Location: Sweden
Not a stupid question at all. I've found when comparing data sheets from Papst that it's actually no difference in sound, unless you have a very unrestricted case, where the sole 120mm fan wins.
The example was using two 12dB 80mm fans against one 26 dB 120 mm fan. Trying this against different impedance curves you would get different pairs of flow/pressure that the 2x80 can deliver, the sound being 12+3 = 15 dB. Reving down the 120 to the same flow pressure would yield the same sound for most impedance curves, except the lower ones.
(NB. If this doesn't make sense to you, I'll find a link explaing how fans work in a PC case.)
(NB2. I will post the diagrams if there is interest, don't have the time right now).
On the other hand, if you need more air than 2x80 can give, 120 is the only option, albeit at the cost of sound.
It boils down to what you can fit in the case, in my opinion. And (!) since my findings are purely theoretical, go ahead and try it in real life, and see what you think.
$ 0.02 from datapappan
The example was using two 12dB 80mm fans against one 26 dB 120 mm fan. Trying this against different impedance curves you would get different pairs of flow/pressure that the 2x80 can deliver, the sound being 12+3 = 15 dB. Reving down the 120 to the same flow pressure would yield the same sound for most impedance curves, except the lower ones.
(NB. If this doesn't make sense to you, I'll find a link explaing how fans work in a PC case.)
(NB2. I will post the diagrams if there is interest, don't have the time right now).
On the other hand, if you need more air than 2x80 can give, 120 is the only option, albeit at the cost of sound.
It boils down to what you can fit in the case, in my opinion. And (!) since my findings are purely theoretical, go ahead and try it in real life, and see what you think.
$ 0.02 from datapappan
My knowlegde of impedance curves is lacking, so please feel free to enlighten me.
At the moment my case has 2 positions for 80mm fans at the rear. My original idea was to simply cut over the 2 80mm "stamped" grills to make a hole for a 120mm fan. But it would be far easier (and look much nicer) to use 2 80mm fans and replace the stamped grills with basic wire grills, hence my original question.
Either way i'll be choosing high speed fans, so i can switch them between 5v (idle) and 12v (gaming, benchmarking etc).
As a point of refererence, an Antec TriCool 120mm Led is rated at 79cfm ; 2000rpm ; 30dB while the 80mm TriCool Led is rated at 34cfm ; 2600rpm ; 30dB. (both set to full speed) So two 80mm fans will be louder and move less air than single 120mm.
At low speed though 2 80's would seem to be quiter. The 120mm moves 39cfm of air while 2 80's moves 40cfm (20cfm each). The 80mm fans are rated at 18dB (so 18+3 = 21dB), while the 120's are rated at 25dB. So at an almost identical cfm the 80's are quieter. That's if Antec's numbers are correct.
But from what i understand, the noise from a 120mm fan is less distracting as it is of lower pitch.
I think i've basically answered my own question here, but i would really appreciate any other comments.
At the moment my case has 2 positions for 80mm fans at the rear. My original idea was to simply cut over the 2 80mm "stamped" grills to make a hole for a 120mm fan. But it would be far easier (and look much nicer) to use 2 80mm fans and replace the stamped grills with basic wire grills, hence my original question.
Either way i'll be choosing high speed fans, so i can switch them between 5v (idle) and 12v (gaming, benchmarking etc).
As a point of refererence, an Antec TriCool 120mm Led is rated at 79cfm ; 2000rpm ; 30dB while the 80mm TriCool Led is rated at 34cfm ; 2600rpm ; 30dB. (both set to full speed) So two 80mm fans will be louder and move less air than single 120mm.
At low speed though 2 80's would seem to be quiter. The 120mm moves 39cfm of air while 2 80's moves 40cfm (20cfm each). The 80mm fans are rated at 18dB (so 18+3 = 21dB), while the 120's are rated at 25dB. So at an almost identical cfm the 80's are quieter. That's if Antec's numbers are correct.
But from what i understand, the noise from a 120mm fan is less distracting as it is of lower pitch.
I think i've basically answered my own question here, but i would really appreciate any other comments.
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StarfishChris
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Ralf Hutter
- SPCR Reviewer
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I'm locking this one.
Not only is the topic covered quite well in the link above this post, there's a Sticky Post right at the top of this very forum, that covers much of the same topic.
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Not only is the topic covered quite well in the link above this post, there's a Sticky Post right at the top of this very forum, that covers much of the same topic.
SEARCH