Can I make a high speed fan near silent(sometimes)?

[fackinlogins]

I am looking for two 120mm fans to cool my dual '77 Bonne heatercore.

I have a nifty fan control thing for the thermaltake volcano cpu fan that fits in an empty floppy drive bay:

http://www.newegg.com/app/Showimage.asp?image=35-106-038-08.jpg/35-106-038-06.jpg/35-106-038-07.jpg/35-106-038-01.JPG&CurImage=35-106-038-07.jpg (the thing on the right)

You guys think I could use it to make a rheostat for 2 12v fans, probably using a transistor? (I have some electrical circuits knowledge, but plain english is my favorite way of learning)

My second question:

Model- Delta AFB1212VHE
Dimensions- 120 X 120 X 38mm
Rated Voltage- 12 VDC
Operating Voltage Range- 4.0-13.2 VDC
Rated Current- 0.6 Amp
Rated Input Power- 7.2 Watt
Speed- 3200 RPM
Max Air Flow- 129.96 CFM
Max Air Pressure- 0.420 IN H2O
Noise- 48 dB-A

I know probably no one knows, but can anyone educatedly guess if these fans could be set so low on the voltage using a homemade rheostat that the noise would drop to the 20's dbA(albiet 30's probably more practical)? Would it still keep my computer from burning up at that low of a speed?

I want to have some super high air flow when things are hot, but then at night keep my computer running near silent.

Maybe this is more trouble than just getting some panaflo m1a's, but I can get those deltas $4 shipped! Would the performance be good, or no?

Any ideas?

[MaxxxRacer]

just get a regular rheobus.. the sunbeam one is 20 bucks to your door if you look around..

and btw, those HE's are not the best of undervolters. ive heard reports that they make some noise.. as to the validity of these claims im not sure but i thought u should know.

btw thats an amazing price on those he's...

[fackinlogins]

I'm poor.... plus I'm curious to see if I can do anything with that knob control.

On those specs, they say they'll go down to 4V but I don't know what they sound like at 4 Volts.

[fackinlogins]

I am supposed to undervolt these fans to make them quieter, or lower their current? I am kind of confused. What is the best performance?

[TekXoID]

Just try it. Chop off the little connector and solder 12v VDC from say a spare molex passthrough to one of the leads on the
rheo (doesn't matter which wire really) and solder both of the fans positive leads to the other wire coming from the rheo.

If it doesn't handle it, the worst that can happen is that the rheo dies and your fans loose power,
in which case your CPU overheat protection would come to work and shut your system down.

[fackinlogins]

Ya, I would in a heartbeat, but I actually haven't bought the delta's yet, because they are 49 dbA, and I want to make sure that at night I can make them go way down to sleep.

[MaxxxRacer]

just run them at 5 volts from the red cable from the psu.. use a molex to connect to the fan.... it will work fine.

[TekXoID]

Might want to get some ThermalTake SmartFan 120's or Enermax Adjustable 120's instead.

Both push out about ~95CFM and are very quiet. (30dB Enermax, lower pressure, 45dB ThermalTake, higher pressure)
Do you really need a fan that can do 120CFM when you don't want to run it at full speed anyway?

[fackinlogins]

Well, If the noise is proportional to the performance then I don't mind the noise while I am working or playing a game. I want them to be silent at night when I sleep, without turning them off, of course. Hence, my struggle.

That, and I can get those deltas for $4 SHIPPED! A very good deal. Enermax's are like near $20 shipped

[MaxxxRacer]

fack, the deltas are NEVER going to be quiet until they are off.. lol... they are designed to be really noisy and really powerful. even undervolting them they will still be noisy from the powerful motor.

[fackinlogins]

Sad day :( will I ever have everything I want all at once....... no, I doubt it.

Well Crap. Now I don't know what to do.

[MaxxxRacer]

the panaflow are a great optioon but you will still ned a fan controler for when u want to sleep.

[fackinlogins]

You think the panaflos would be silent as a sleeping cat atleast at low power, but still cool it enough for idle temps that won't kill my computer?

And then cool down my oc'd stuff(athlon and fx5950) when I'm on a full load at 12v?

[MaxxxRacer]

yep.. u wont even need 12volts... to be honest, i run my denkis (which are relatively comparable to the panaflows) at 5.5-6.5 volts most of the time.. they are very quiet and very sleepable at those voltages... but much below 5 volts and they turn off.

[fackinlogins]

one last question, You say you run them at 5.5 volts, but How do you control that? What is the difference between controlling the voltage and putting a variable resistor to reduce the current? Does anyone know? I know the formula R=V/I but a fan isn't entirely a resistor, so that Is why I am wondering about the speed control method.

[MaxxxRacer]

with a VR you will adjust the voltage not the current AFAIK.

the rehobus that i use just uses VR's if i remember correctly. some hefty ones at that though.

btw, i use the sunbeam controller.. there are pics in several places if you want them of my setup with the controller...

[fackinlogins]

http://www.ocforums.com/showthread.php?t=351815&page=1&pp=30

There is a good post about making fan controllers. If I was a bit smarter I could find a way to incorporate that TT controller into one of those circuits.... alas I may blow something up before its all done.

Which is why I have decided to experiment with the deltas before buying the panaflo's.
Ruining a $4 fan seems so much better than a $15 fan.

If anyone wants to help me, let me know. I'll post pics after I am done. I don't have the fans yet, but I want to plan the circuit, so if anyone wants to look at the last post over at ocforums, it explains what I am trying to do....

[Holst]

The problem with those deltas is that they wont spin up as easy on lower voltage... so you might not be able to get them as quiet as you want.

If you use a PWM controller you might be able to get them running a bit slower.

But dont expect to get them super quiet... you will get them from stupid loud to quietish

[fackinlogins]

Aight, well, I may be going for these guys instead, since I may not be able to get those ones for $4 shipped, these (WFB1212ME) would be about $6 instead:

http://www.excess-solutions.com/SpecSheets/120mm%20Series.htm

They are a little more quiet, but their not as powerful. The only problem? they only have an operating voltage of 7-13.2V, those other were supposed to go down to 4V.

Opinons?

[MaxxxRacer]

the ME's should be considerably quieter.. you wont need to undervolt them as much. at 7 volt they should be ok.