I have built plenty of boxes in the past but never for spl , how would I go about it with out a term lab or is it possible to do it , could I build box say at 6 cf build removable port use a small hand held db mic , and test then trim and repeat tell the #s don't get higher , always using same tone from deck at same low volume ? Would that work or is there a better or even a right way to do it with out term lab ?