I think you mean the VP150. I don't design speakers that's for sure, but porting is used for the bass response of a speaker/cabinet. The M2i and other smaller speakers are used as mains in many set-ups, and they are also used as rears, etc. But are (unless used as a center) responsible for the full spectrum, lows=bass, and highs, where as a center is used for dialouge, voices, lesser non-bass frequencies. Even on SACD recordings, 5.1 for music, the bass notes are steered to the mains/sub. Porting allows for better cone excursion in the cabinet (cone rapidly moving back and forth) it lets the speaker "brethe"
The center channel does not experience these notes to the degree mains/subs do. Although on 5.1 music I can see the little 4-1/2 cones moving a bit at higher volumes.
