That little of a difference isn't going to matter much. WOW, the box i have now is 2.58, going to 2.70 isnt gunna make a difference :/ so now its like ported or nothing... Why would you want to go from 2.58 to 2.7? im not gunna, that was really stupid of me, i was calculating my box TOTALLY wrong and it seemed like there was a difference but i see now there is none. i really want a ported box, but how do i calculate the cu.ft of a ported box? If you run Windows, or have a way of running Windows programs on your Mac, I would highly suggest getting the Torres' Box Tuning Calculator. You put in your dimensions and it does all of the calculations for you. If you don't know what to put in a specific field, go to the help menu and any questions should be answered. Good luck! i've tried downloading that before, for some reason the download always fails