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<blockquote data-quote="OLD_SCHOOL" data-source="post: 533838" data-attributes="member: 556272">the 13.5 is 12 inches + 1.5 inches of mdf that gives you your second wall length.. it changed size because we just used an arbitrary number of 12 inches because your displacement will always be the same as long as it is an l shaped portsee lets do it with a depth of 15 inches this timeso for port wall 1 it is just internal depth - port width 15-2=13inchesfor port wall 2 its physical lv - external depth so 34.5 - (15+1.5)=18 inches longnow figure displacementsport wall 1 16 * (2+.75) * 13 =.3310ft^3port wall 2 16 * (2 +.75) * 18 = .45833 ft^3those two added togther = .789351 ft^3same as the first two displacements we found using a 12 inch depth 5347 + .2546 = .7893 ft^3so see we wernt using any special depth at this point we are just trying to figure out the displacement of the second port wall once you have that then you can figure your bxso we are going to come up with the same gross box volume every time all that will need to be adjusted is the port wall length ALSO these figures don&#039;t include bracing you have to account for those as well in your final dispalcementand yes squeak is right it is best to start off with a net volume and add your stuff than try to figure out a round figure and subtractnow what i want to learn is how to figure he length and displacement on ports that hve 3 walls</blockquote>

[QUOTE="OLD_SCHOOL, post: 533838, member: 556272"] the 13.5 is 12 inches + 1.5 inches of mdf that gives you your second wall length.. it changed size because we just used an arbitrary number of 12 inches because your displacement will always be the same as long as it is an l shaped port see lets do it with a depth of 15 inches this time so for port wall 1 it is just internal depth - port width 15-2=13inches for port wall 2 its physical lv - external depth so 34.5 - (15+1.5)=18 inches long now figure displacements port wall 1 16 * (2+.75) * 13 =.3310ft^3 port wall 2 16 * (2 +.75) * 18 = .45833 ft^3 those two added togther = .789351 ft^3 same as the first two displacements we found using a 12 inch depth 5347 + .2546 = .7893 ft^3 so see we wernt using any special depth at this point we are just trying to figure out the displacement of the second port wall once you have that then you can figure your bx so we are going to come up with the same gross box volume every time all that will need to be adjusted is the port wall length ALSO these figures don't include bracing you have to account for those as well in your final dispalcement and yes squeak is right it is best to start off with a net volume and add your stuff than try to figure out a round figure and subtract now what i want to learn is how to figure he length and displacement on ports that hve 3 walls [/QUOTE]

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