Some drivers can handle both ported and sealed enclosures, some cannot. Also, when plugging a port, you want to plug the whole length. That applies to more than just speakers ;-)
Protip: Using a sub? Plug your mains
Merry holidays, or drinking season, whichever you celebrate I support you.
For those of you with ported main speakers and subs, here’s a big tip: Plug your main speakers.
It will reduce the bass output, but also greatly reduce the movement of the driver below the port frequency. This combination increases the dynamic range, and reduces distortion, especially when used with a line level high pass filter. It also often makes integrating the subs easier thanks to less overlap. Use a sock, preferably yours and clean unless you are some weirdo. You don’t have to stuff the entire port length, just plug the end tight. I won’t be held responsible for those of you who lose their intimates inside their speakers.