How deep is the port? For a single sub that should work but, if you are moving a lot of power/air then it may be too narrow. I have used a flared port whenever possible. Haven't had an issue with port noise yet using one of them. However, I have heard a ton of rectangle/slotted ports and they don't have noise either.do you think a 8 by 2.5 inch rectangle port is too small ffor a 400 watt 12" sub?