Second grow area (exhaust fan question)

I'm looking at making a spare closet into a second flowering room. It's about 2x4x7ft and I was planning on using one 300w LED light. But I may have to use a second LED or a few CFLs to get full light to the whole area.
Anyway, I'm thinking I'll probably just use a small 4" duct fan rated at 100cfm to pull a little air out and into the surrounding room. But I shouldn't need to run it full speed to control heat so I'm looking at variable speed controllers. Supposedly, the controllers that run the centrifugal style fans (like I use on the main tent)...won't work on the inline duct fans.
Anybody know which controllers I should be looking for?
Thanks

https://www.amazon.com/YaeCCC-Transformer-Variable-Voltage-Regulator/dp/B078W4YG3B/ref=sr_1_12_sspa?ie=UTF8&qid=1533009872&sr=8-12-spons&keywords=variac+variable+transformer&psc=1

This is what I have and its night and day compared to those cheap fire hazard rebranded pos you find for like $20-30. I feel like I may have gotten mine a bit cheaper and if you only need to control the 4" the 20A is probably a little overkill lol Handy as hell though and idc what anybody says I swear a larger fan turned down is quieter than a smaller fan at full speed

I agree bigger fan slow quieter than small fan high...

But for any:

Put back in its box, cut holes for the ducts and hook it up, pull chord out and fill the box with sprayfoam (prob only like 2/3 for expansion)... once dry cut off tbe overfow close box back up. Wrap in foil of some sort if you want it to liik nice, quiets em way down. No they dont overheat as motor is cooled by the air its blowing over it in the fan.. quiets e m more if you run insulated flexible duct... full speed my be fine.

Huckster79 said:

I agree bigger fan slow quieter than small fan high...

But for any:

Put back in its box, cut holes for the ducts and hook it up, pull chord out and fill the box with sprayfoam (prob only like 2/3 for expansion)... once dry cut off tbe overfow close box back up. Wrap in foil of some sort if you want it to liik nice, quiets em way down. No they dont overheat as motor is cooled by the air its blowing over it in the fan.. quiets e m more if you run insulated flexible duct... full speed my be fine.

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This sounds like a good idea. My 6" fan for the light hood in my main tent is pretty loud....and I have it running on low.

tst2015 said:

This sounds like a good idea. My 6" fan for the light hood in my main tent is pretty loud....and I have it running on low.

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I took my speed switch out... been running a few years aweful damn quiet full bore and its just a generic amazon model... its a great trick im glad i stumbled on, and it costs about $10 to pull off...

tst2015 said:

This sounds like a good idea. My 6" fan for the light hood in my main tent is pretty loud....and I have it running on low.

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My favorite part about that 20A model that I linked is that it can safely handle a couple fans in case you wanted to control the main tent also

Oh suspending em from a bungy cord buys you a few more decibles for a buck

Huckster79 said:

Oh suspending em from a bungy cord buys you a few more decibles for a buck

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I've got mine sitting on top the tent on support bars. Maybe I'm getting some sound from that...I'll have to check it out.
The 6" is overkill for my light anyway but my 4" fan is for the 4" carbon filter to outside.
I tried running carbon filter > light hood > 4" fan > outside but it wouldn't keep tent cool enough. So I ran a two fan setup. Using it for veg at 450w right now so haven't even been using the carbon exhaust...just the light cooling has been keeping temp down.

tst2015 said:

I've got mine sitting on top the tent on support bars. Maybe I'm getting some sound from that...I'll have to check it out.
The 6" is overkill for my light anyway but my 4" fan is for the 4" carbon filter to outside.
I tried running carbon filter > light hood > 4" fan > outside but it wouldn't keep tent cool enough. So I ran a two fan setup. Using it for veg at 450w right now so haven't even been using the carbon exhaust...just the light cooling has been keeping temp down.

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I'll bet you that dollar bungy cord that resting on that support bar is adding to the sound...