Well I trust svs to make a feature and stand by it. Or else they would get in trouble for it.
Anyways, back to ported mode it goes.
Look into enclosure design for low frequencies- the driver dictates the internal volume and if needed, the port tuning, which is based on diameter and length. If a port is used, its volume must be added to the enclosure's internal volume. Depending on the wants & needs of the system and the driver's T/S parameters like cone mass, QTs, VAS, etc, the internal volume determines the Q of the system. Close the port and that changes. Make a box smaller and the Q increases, make the box larger and the Q decreases. .707 is ideal WRT response without ringing- high Q creates a peak that can be obtrusive and if it's too high and its F3 clashes with the main speakers, it can be a 'one note wonder' all alone in the wilderness or it can cause constructive/destructive interference in the area where it overlaps with the main speaker's woofer response.
Unless SVS deals withall of this in a direct and distinct way, just shoving a piece of foam into the port isn't going to be the best way to deal with this. It can, however, slow the air movement without completely screwing up the Q but closing the port chops a good amount of response off of the low end.
