I think your misunderstanding my question. I had a design and that was it. the max volume of the not counting the port was about 1.5 cubes. I need to calculate the space the port takes up. my goal was to stay near 1.25 cubes.//content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif How do you NOT know what the internal volume is? You need a design to use SketchUp properly, I wish people would listen. It doesn't have anything at all to do with audio, and is completely unnecessary.