How did i come up with that you may ask ? its easy I"m sure you already know all the math, just some new formulas
Box Tuned Frequency
Qtc is the over all Q Ratio i was talking about before
Fc= (Qtc)(Fs)/Qts
Box Volume is a little more tricky
You find the constant for that speaker and That overall Q (Qtc)
Constant = ((Qtc/Qts)^2 ) -1
then Constant = Vas / Vb (both must be the same so if Liters keep liters, if cubic feet, keep cubic feet)