Thought this woudl be a agood topic for cab builders discussion. there are scads of DIY calculators and programs that will aid someone in tuning a round port. there are end corrections for flared round ports. Ditto for tuning a square/rectangular port . There are also easily obtainable calcultors for slot ports. HOWEVER, i have been unable to find a calculator for tuning slot ports that are triangular in cross section. I am off to see what vance has to say about this, and to find a generic cab tuning / port tuning equation. I am guessing i can then fit any shape to this, since it should be a function of cross sectional area and length. (but then again different cross sectional shapes will have differing resistance to air flow... is it significant?