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<blockquote data-quote="wu501" data-source="post: 545798" data-attributes="member: 553825">okay, i looked up some of jmacs posts and im still getting closer to what i said.Originally Posted by JmacMeh, calculators **** ... Use a sheet of paper and a pen, draw out your enclosure, make sure it&#039;s right ...Here&#039;s a step-by-step process of how I do it ...1) Measure your trunk for max dimensions and note TWO dimensions that would be preferable. Subtract twice the thickness of the desired dimensions to get the desired internal dimensions (i.e. 3/4&quot; MDF, 20&quot; height = 18.5&quot;)2) Figure out desired net volume, tuning frequency, and port area.3) Figure out port length using the following formula :Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av)Lv = Port Length in inchesAv = Port Area in square inchesVb = Net Internal Volume in cubic feetFb = Desired Tuning Frequency4) Draw out a diagram of your enclosure on a sheet of paper and figure out the displacement of the port.5) Add up all displacements (port, driver, brace)6) Add displacements to desired net volume and multiply by 17287) Divide by the two desired interal dimensions to get the third internal dimension8) Add twice the thickness of the wood to get the exterior dimensionsokay the box is 28&quot;w x 22&quot;d x 18&quot;h. this comes out to 5.187 cubes internal before port/sub/bracing displacement.So i took his formula for port length and here is what i got:40*1.84*10^8/[5.187*1728*(30/0.159)^2]=23.0658555219959So where are uo coming up with these longer lengths? Please help me.</blockquote>

[QUOTE="wu501, post: 545798, member: 553825"] okay, i looked up some of jmacs posts and im still getting closer to what i said. Originally Posted by Jmac Meh, calculators **** ... Use a sheet of paper and a pen, draw out your enclosure, make sure it's right ... Here's a step-by-step process of how I do it ... 1) Measure your trunk for max dimensions and note TWO dimensions that would be preferable. Subtract twice the thickness of the desired dimensions to get the desired internal dimensions (i.e. 3/4" MDF, 20" height = 18.5") 2) Figure out desired net volume, tuning frequency, and port area. 3) Figure out port length using the following formula : Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2] - 0.823*sqrt(Av) Lv = Port Length in inches Av = Port Area in square inches Vb = Net Internal Volume in cubic feet Fb = Desired Tuning Frequency 4) Draw out a diagram of your enclosure on a sheet of paper and figure out the displacement of the port. 5) Add up all displacements (port, driver, brace) 6) Add displacements to desired net volume and multiply by 1728 7) Divide by the two desired interal dimensions to get the third internal dimension 8) Add twice the thickness of the wood to get the exterior dimensions okay the box is 28"w x 22"d x 18"h. this comes out to 5.187 cubes internal before port/sub/bracing displacement. So i took his formula for port length and here is what i got: 40*1.84*10^8/[5.187*1728*(30/0.159)^2]=23.0658555219959 So where are uo coming up with these longer lengths? Please help me. [/QUOTE]

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