6" to 4" reducer, CFM loss?

[captain crunch]

How much of a restriction am i creating if i use a reducer between my fan and carbon filter? Would it make a difference how far the reducer is placed from the fan? Am i better off using 6" ducting and a 6" carbon filter?

 

[ginjawarrior]

How much of a restriction am i creating if i use a reducer between my fan and carbon filter? Would it make a difference how far the reducer is placed from the fan? Am i better off using 6" ducting and a 6" carbon filter?

depends on what your trying to cool but even so you'd be much better off with the 6 inch ducting and filter. i had 4 inch acoustic ducting so i tried to use a 6 inch fan with reducer with 8 inch carbon filter but the airflow was so restriceted the fan had to run on full wack, it sounded like a jet in my room and i had still had trouble with heat
i then bought some 6 inch standard ducting fitted that to the fan and now i can run fan on low and its really quiet even tho i'm not using acoustic duct