Why is it bad to have the height to width ratio larger than 1:8? I made a box that is too small.... and thats the only i really can make my box tund low enough... i fucked up and now im out 2 sheets of mdf and a lot of time and effort... damn..

"The ratio of W to h should not be any more than 9 to 1 to prevent tuning shifts introduced by excessive friction between the rapidly moving air and the port's surface. It should be noted that this is not a hard-and-fast rule, merely a rule of thumb to help you prevent a mis-tuning. In short, keep the port as square as aesthetically and physically possible."

So if my port was 18.125" x 2.25" is it gunna mezsed up?

That is still below 9, so should not be a problem.

I have made them as much as 12:1 and they still worked (and measured) correctly. You will be OK.

I have made them as much as 12:1 and they still worked (and measured) correctly. You will be OK.

I'm about to make one almost to that ratio as well.

I wouldn't worry about it. Just don't undersize it as well.