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I recently puchased a couple of real whisper fans on Ebay from this seller:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %26otn%3D4

They work great but I was wondering if there is a relatively easy way to slow down the speed of the fan to make them a bit quieter.
As you may be able to see, these fans come with a captive power cord. Any ideas?

Thanks!

I remember reading that the way to slow down an AC fan is
to put a capacitor in series, like .5 to 1 mfd, rated for at least
250 VAC I suppose. Those fans don't draw much current,
and the capacitor will work well.

Wire them in series and see how they work?

I remember reading that the way to slow down an AC fan is
to put a capacitor in series, like .5 to 1 mfd, rated for at least
250 VAC I suppose. Those fans don't draw much current,
and the capacitor will work well.

Thanks, Tom. So I could just splice it into the AC cord (with suitable insulation of course)?
I suppose I would need to just mess around with the value of the cap until I found one that provided the speed
I was after...?

Thanks,
Joe

Yep - just stick it inline ... I usually hide things like that
inside one of those Radio Shack black plastic boxes.

... tom

Well, I had a couple of 0.47uf/630vdc Wima film caps laying around so I tried one of those. I believe that a rough
rule of thumb for AC voltage ratings on DC-rated caps is about 40-50% so I figured this was safe...at least for a trial
run. I wired it up in line and the fan didn't run at all. Took out the cap and the fan ran fine again.

Oh well, back to the drawing board...

Thanks,
Joe

I don't remember the original source of the capacitor idea ...
I just found this online ... same idea ...

" I built a cabinet for a few pcs but the fan is too noisy and soft
mounts haven't worked, any way to vary the speed of this motor?
Router speed control and incandescent light dimmer won't work, is the
only way to go DC12v w/ rheostat?


I've done this by putting plastic film or oil-paper capacitors in series
with them. Usually something in the 0.1 to 0.47 uF range, 250 V
minimum rating. It is fairly tricky to find the right value as the
backpressure load on the fan greatly affects the speed when you run
it like this.

The best solution is if you can get a Rotron "Whisper" fan, it will turn
very slowly and can rarely be heard except in a silent room."

Thought I'd revive this thread as I've had a chance to mess around with this some more.

The best solution is if you can get a Rotron "Whisper"
fan, it will turn very slowly and can rarely be heard except in a silent room.

That's what I have - it's a real Rotron Whisper. It turns fairly quickly actually...I guess
it depends what one means by quickly. Yellow_Light_Colorz_PDT_08 I'm using it in my bedroom system and I
could hear it with music at moderate volume as it's pretty close to my bed.

Anyway - I decided to mess with the amount of capacitance and found that paralleling two
of the 0.47uf 630v caps (so 0.94uf total) and putting that in series did the trick. Works like a
charm and is much quieter. I took your advice and put them in one of those Radio Shack
project boxes...looks much better and runs nice and cool.

Thanks for the tip, Tom!

Thanks for the update Joe ! Sal just bought an SCA-35, and
needs to cool it down. He wants to use some 10 for a dollar
CPU fans on it, but I think they will melt. A REAL Whisper
fan is the only way to go, so about 1 mfd at 600 volts is
probably a good target value.

Correction Tom,
10 for free is more like it... you should know me by now... Yellow_Light_Colorz_PDT_01

I used to come across the real metal whisper fans at work all the time but no more... but I think I have 2 NOS ones in my garage.

Sal

***EDIT***

I think I solved the heat issue with my Dynaco SCA-35... Yellow_Light_Colorz_PDT_07