Recently built a box for a 12"sig using the 12volt port calculator-2.85 cubes with a 3.125"x15" slot 24.75" long which would put me at 38Hz or so. It is a side firing port running the back of the box.
Guy i know at a recent show has a term lab and we did some testing- the box seems to be tuned to 34-35Hz but i know mathamatically it is tuned to 38. the guy was saying that the the back of the box continuing beyond the port will make the port length seem longer
-makes sense to me.
Now what im thinking is cutting out a peice of the back of the box for burps-maybe make the port 20" long. then i could fit in a removeable peice to bring it back to a daily box.
thanks for any help or comments