just as long as its not directly opposite the sub it should be fine. typically its up top or on the front. some people say its louder on the sides. and obviously the bottom isn't good, lol. i don't know which is best though
I ported a Camaro enclosure on the side after reading an article that stated you can put the port anywhere in the enclosure as long as it's not a certain length away from the sub (this caused frequency interferance) There was a nice chart as well to show you what frequencies would be interfered with at what distances and all of them were larger than the dimensions on my enclosure. The guy also said he likes the ports to not be in the front with the subwoofer because you hear more of the extra stuff that happens from the back of the cone. In any event the Camaro box worked excellent with the side vents and it's sweet because no one knows it's a ported box.