I know this thread is cold but a lot of people view it so if you have the answers please post!

1. Tokudai mentions that the calculation parameters are more relaxed for a "complete room." His cabinet size for the example was 2x2x6. At what size do the parameters shift? 4x4x6? 8x8x7?

2. Does anyone know the multiplier for adding a reduction in this scheme? What does stepping down from a 6" to a 4" duct do? Obviously this creates additional load on the fan but how can that be calculated?

One additional thought - you could add a duct iris to the passive intake. Coupled with a speed controller for the fan you should be able to micro adjust air pressure to an optimal point. They are a little pricey though...

Also, the Noob's guide to grow room setup also has some good examples of how to calculate fan needs. Find it here: http://boards.cannabis.com/indoor-gr...-progress.html