How do i slow down my exhaust fan???

i have a 4 in centrifugal pump with a 4x12 phat filter for a 35 cubic foot box. this filter/pump is good for much higher volumes. Now i made a bomb DIY muffler system which kills 99 percent of noise from the fan and exhaust duct the problem is the filter is inside my relatively small grow box and the sound of air rushing into the filter is by FAR the loudest part. I would think my remedy would be to slow down the fan to decrease airflow since this system does much more than it needs to for my setup. i just dont need that extra airflow and would rather have silence... So how do i limit the speed of the fan without hacking up the cord and doing something ghetto. is there some kind of switch i can buy that would give me good control???? Specific examples appreciated.Thanks all.

im not positive but im sure there is some sort of dimmer switch type thing

This should do it..

http://www.amazon.com/Speedster-variable-Fan-speed-control/dp/B000HQAVNI/ref=sr_1_1?ie=UTF8&s=miscellaneous&qid=1302672564&sr=8-1

Apologies if it's not kosher to post a link like that...

http://http://www.plantlightinghydroponics.com/fantech-variable-speed-fan-control-p-1487.html

This is what u r looking for. I have 2 and they work great.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=400147432708&hlp=false&rvr_id=224730688935&crlp=1_263602_304652&UA=?*F?&GUID=18419bf712e0a47a2430a960fe356fc6&itemid=400147432708&ff4=263602_304652

Can often find them at WalMart, hardware stores, and sometimes super markets.

PERFECT thanks a bunch everybody, this is why i love RUI.

splice in a dimmer switch.....

you can buy one already wired up for a lot more or make your own just about any rheostat will work. that is all you are paying for.

Just be careful what dimmer you use, I know that I was, and am pushing the limit on my power supply so when I put my fan on the dimmer after an hour or so it blow the breaker....as of now the 440cfm goin at full speed keeps my room nice and cool...

So just be aware that if you plan on using a dimmer realize it put's more load on the breaker because it's creating resistence.....Def not claiming to be any sort of expert though

People often complain with the speed controller that it creates a strange hum in the fan which itself is pretty loud. Many people say to keep this from happening you need to use a variac controller which doesn't just add resistance to the line or like the speed controller just turn off and on the socket.

I use this, http://www.growwurks.com/tmp-dne-day-night-temperature-control.aspx and couldn't be happier with it. It allows me to cool alittle more in the off time to simulate dips in temps during flowering outdoors. It also slowly ramps up to speed and then back down when it gets close to the temp you desire.
Let us know what you go with and if you have the dreaded 'hum'.....

got a ext cord one for 8 bucks. 300w max the fan is 98w. My whole setup is 530w including fan with an additional 350w of stuff running on that circuit. a 15 amp breaker which is most common should be a 1800w max with 1440w being the 80% safe max, so i should be in the clear. If I'm wrong PLEASE correct me. Feel free to comment or add information. Another question that came up (thanks Moose) is how much the resistance of the dimmer would increase the effective wattage of my setup and if it would be substantial or not. with only 98 watts max hooked up to it I would not think so but I'm not electrician so chime in if you know!

Pricey but this is what would be ideal: VSC-DNE - Day/Night Fan Speed Controller - $66