passive vs. active intake

[minigreens]

i'm wondering whether to set up active or passive intakes for my new cabs. I was going to have 120mm intake and 120mm exhaust...but if i put a scrubber on the exhaust then i will get backed up, right?

so how big of holes would i need to get teh right amount of suction with a passive intake if i'm using a 120mm fan with a scrubber?

 

[wishbone420]

i would use more smaller holes. start with 2 p.i. holes to 1 exhaust. run the lights check temps and make more till u find the sweet spot. intake should be at bottom of box while exhaust should be at top. if possible have seperate space for lights.

heres my exhaust

 

[jrw]

Intake should be twice the size of your exhaust - i.e. 1x120mm exhaust, 2x120mm intake.

Passive intake is preferrable, to prevent pressure to build up in the cabinet, compromising odour control.

 

[Mr_Micro]

Indeed, I've found passive intakes to be much easier to work with than active ones. Mainly because you don't have to worry about pressure build up in the cab but also because it allows you more space to work with in your cab when you don't have to worry about keeping planters and whatnot far enough away from a intake fan to not restrict it.

Anyhoo, having an intake twice the size of your exhaust is always good but I've had plenty of success with intakes that are 1 to 1.5 times the size of my exhaust. For this purpose in PC cases (where you might not have enough space to put in a bunch of plumbing elbows) I recommend 4" darkroom midget louvers. They're easy to install and will let air in but also act as a light trap to keep light from escaping. At about $10 USD each they're a bit expensive but very cool items indeed.

 

[Pig-Pen]

Passive. Even when building and working full rooms I always used passive. Main reason being, as mentioned, odor control. I've always done intake = exhaust. If your intake is too big it will be hard to achieve strong negative pressure., However if it's too small you will restrict the fan and overall airflow as a result. So 1:1 has always worked well for me.

If you have a 4" circular exhaust for instance, that gives you an area of 12.5" square inches. So you would want roughly 12" square inches for your intake. A 2" circle is about 3 square inches, so you would need 4 of them to get the same area as your 4" exhaust.

 

[jrw]

Here's one way to make a good passive intake that don't take up much room.

 

[minigreens]

very nice jrw! sweet set up

thanks for the help everyone, good stuff