I understand you just need to know where the numbers are being skewed. After you enter in port dims does your app ask for port wall thickness ? Your first calculation for port was 11.5*22.5*5.25=.786 but if it used this number it was alrdy off by .11 because 11.5*22.5*6(.75 more displaced by outer port wall) = .898 L shaped ports utilize the outer wall and dont have to account for one wall of displacement' date=' center ports displace more volume because of the extra wall on each side. Most calculators cant see your box config(floorplan) they will just assume its a straight port 22.5" long. Anytime you use a flared port it does not count as port length but this is minimal as a general rule add another inch to the port if its flared to account for the radius. I suspect the small differences are adding up.[/quote']
Yes it asked for port thickness. It also asks for common walls, external port length, displacements of sub's, displacement of bracing. It asks everything... My port is just a straight port, no L and no flare.