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View Full Version : Single 120 vs Dual 80s CFMs and Sound level


mfpmax
10-13-2002, 12:57 PM
Since these are fans...i'm posting it here :) But it seems I may run into space problems in the area where my fans will be mounted so I thought about using 2 80mm fans instead...

The single 120 fan produces 86 CFM at 35dB
The single 80mm fan produces 39 CFM at 32, but will be setup in a Dual arrangement.

Now my question, will the Dual 80s produce similar numbers of the single 120, such as producing about 80 CFM at the same noise level. Cause i'm not all up on the math, I just know I want the flow but not sure of the outcome. And just so you know, I won't be stacking the fans, they'll be sitting side by side.

pHaestus
10-13-2002, 01:14 PM
Search for P-Q curves for the fans in question. You can pick a few resistances and then look at the resulting airflow that the fans would produce.

mfpmax
10-13-2002, 01:18 PM
Originally posted by pHaestus
Search for P-Q curves for the fans in question. You can pick a few resistances and then look at the resulting airflow that the fans would produce.

So you want me to hurt my head :D

Okay, I'll see what I can do, i've got the docs for the 120 fan, i'll go get the 80 fan docs later.

mfpmax
10-13-2002, 01:35 PM
BTW, these will be used in a pull configuration on a heatercore and be installed on a shroud.

The 120 fan is a M1A
The 80 fan is a H1A

Bignuts
10-13-2002, 03:55 PM
The real difference in these two fan setups will be the pitch. I have, but no longer used because of the noise, a 120 M1A. I also have a 80 L1A that is the quietest 12v fan I have ever used, no matter what the size.

I have found that larger fans may sound louder to a SPL meter, but for me the higher pitch of smaller fans drives me bonkers, even if they spec out quieter.

In addition, larger fans in general can pull the air through radiators better because the depth of the blades makes for better P-Q curves.

My current setup is a single 120 L1A, pulling through a DDen Cooling cube, and it does the job quieter than a air setup, but if I were to do it again I would use a setup that can hold 4 120 L1A's and with a radiator with a face surface area of 144-240 sq inches. I figure that is what it will take to get my temps down to where I want them, and be silent at ~7volts to the fans.

mfpmax
10-13-2002, 04:28 PM
Yeah, the two 80s combined whine may cause sucidie :D

I did notice that though, I had some Nidec 80s in my first setup long ago, switch to dual 120s...the dual 120s were louder but less annoying.