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Question about Fan Sizes'..............

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Crispy

Member
Joined
Feb 2, 2001
Location
Midwest
THis may sound dumb to some, but I was looking in a catalog for Case fans, but the List the Size of them in something besides mm. So I want to know is, is a 4.68x4.68x1.00 a 120mm Fan? And...Is 50CFM and 25dBa Good for a Fan that size? It's a Sleeve bearing. And only $6.95 So can someone help me out here? Thank You
 

Rob Cork

Senior Member
Joined
Dec 17, 2000
Location
Woodcote, UK
Yeah, that's probably 4.68", or 11.9mm. 50cfm is pretty low for a 120mm fan, but 25db is correspondingly very quiet - you probably won't hear it over the cpu fan and the hard drive, psu fan etc... I have three 105cfm 120mm fans, but I'm running them at about 7V (24 Ohm rheostats) to keep the noise down, it doesn't affect temps at all. I do have a 131cfm 120mm, but it's so loud I don't use it at all. I'd consider 67cfm a reasonable figure for a 120mm fan - good compromise between noise and airflow - but if you really need it to be quiet, get that one you mentioned :)
 
OP
C

Crispy

Member
Joined
Feb 2, 2001
Location
Midwest
What dBa level do fans usually become loud? Like is 50 dBa Loud? so should I go for one in the 35 dBa area? thanks for the help
 

Phil

Senior Member
Joined
Jan 13, 2001
Location
Bolton, UK
A hair dryer is probabally about 37-38db, anything under 30db is pretty quiet. The delta fan which is the most annoying sound I have ever heard is 35db but has a strange whirling sound that drives you mad.
db's are measure like the richtor scale for earth quakes, 20db isn't 2X as loud as 10db I can't remember the scale exactly so if some one wants to fill in here.....
 

Fink

Member
Joined
Dec 18, 2000
It's not the size of the fan... but how you use it.

2.54 cm/inch, learn it, live it, love it.
 

kunno

Registered
Joined
Jan 18, 2001
Phil, your wrong about the delta, The delta puts out 38 cfm at 47.5 dba. That means that in scale, your other mesurments are wrong too.
For every increase of 10 dba's, the loudness doubles.
20 is twice as loud as 10 dba's. 30 is twice as loud as 20.
 
OP
C

Crispy

Member
Joined
Feb 2, 2001
Location
Midwest
So How Loud Is Annoying Loud? At what dBa does it get just Unbearable? Oh yeah these Fans will be hooked up to some 7V/12V Baybus Switches. So with that said does it matter what size I get since I can turn them down? WHat the Highest CFM and dBa do people have with a 7V/12V switch? Should I get a Fan that can do 170 CFM with 49 dBa? Even though I know that's loud..Won't it quiet done while only running 7V? and won't it still throw out alot of CFM? By the way...what's CFM stand for? Cubic Feet per Minute? Just wondering. Thank for the help guys
oh yeah I'd like to know what kind/size of fans you guys use and what you think of them....Thank you