Help quieting a 92mm fan

[JediJorgie]

I'm looking to make my 92mm, 12V fan quieter, if possible. I've heard people talking about adding resistors to decrease the noise, and in my searching of the forum, I haven't seen any clear explanation of how to do it, just references. I haven't done any work with resistors and what not for about 4 years, so any advice you can give would be appreciated.

 

[Tiamat]

the zalman fanmate does the job. As for doing it yourself, i cannot be of any assistace.

 

[pirred908]

is the noise comming from the fan directly, or is it comming from the vibration between the case and the fan enclosure? If its the second one, than they sell spacers that can dampen the vibration. If its the first choice, maybe a fan controller? Sorry I can't be more of help.

 

[JediJorgie]

Its the fan itself I want to quiet. I've already got rubber spacers between all my fans and the case. I've thought about a fan controller, but I'd rather have something permanent, like a resistor in the line. If I loose some CFM, so be it.

 

[xbassman]

You can reduce the fan voltage without buying anything except maybe a Molex removal tool.
Here's a thread that it was being discussed:
http://forums.anandtech.com/messageview.cfm?catid=28&threadid=1361212&highlight_key=y&keyword1=7v%20fan

 

[Cheetah8799]

You can reduce the fan voltage without buying anything except maybe a Molex removal tool.

Or use a un-bent paperclip, or super small screwdriver.

If it's only one fan, then this might be the best and cheapest option. You can change it from 12v to 7v or 5v by simply switching around the wires in the molex connector.

 

[Navid]

You need a soldering iron and some resistors.

Look at the fan description or read the sticker on it. Find out the power rating. Say it is 1W. Then divide the power, in Watts, by the 12-V voltage. This will be the current of the fan (Power=Voltage x Current). In this example, it is 1/12=83mA.
Divide the 12-V voltage by the current. This will be the effective resistance of the fan (Voltage=Current x Resistance). In this example, it is 12/0.083=145 Ohms.

Let's say, you want to reduce the voltage to 8V. So, you want 8V across the fan, and you know its resistance. This means that you have to reduce the current to 8/145=55mA. To do this, you have to increase the total resistance to 12/0.055=218 Ohms.

When you have two resistors in series, the overall resistance is equal to the sum of the two. So, the resistance that you have to add is 218-145=73 Ohms.

Go to Radio Shack and buy packages of 5 of resistors around the value you need (56, 100 and 150 Ohms). Each package is about $1 or less.

Cut the red wire of the fan. Use a wire cutter and remove the cover of the wire (1/8" length) so that you can solder to it. Solder the two ends of the resistor to the two wire ends that you created by cutting the red wire. So, now, the resistor is in the way of the red wire.

The 12-V voltage is now split between the fan and the resistor. This reduces the RPM and as a result the noise. Obviously, the amount of moved air is reduced too.

If you are curious as to what the voltage is across the fan, you can use a volt-meter and measure it while the fan is running.

You can try different resistor to see which one is better. After you are done and are happy, make sure to cover the exposed ends of the resitor with electric tape.

The problem with using the 5-V and 12-V wires to achieve a 7-V source is that the current will flow from the 12V side to the 5V side. That is OK as long as there is always a load on the 5V side to absorb this current. But, under some circumstances (high fan current and low load current on the 5V side), this is not the case and the end result is that the 12V supply will be effectively charging the 5V side. Not every power supply can operate properly under such a condition.

Another limitation of this 12-5 approach is that you will be limited to a 7V voltage only. With resistors, you have a choice for the voltage. You may not want to drop the voltage to 7. It may be sufficient to drop it to 10 to reduce the noise without reducing the air flow too much.