If the recommended enclosure for a sub was 1.7cu.ft and you were building a box for two of the subs, would you just double the 1.7cu.ft and have one big chamber? or build the box with two seperate chambers?
You could have one big chamber, it would be fine. The only thing is if one sub ever blows/pops the other sub would be running in twice it's recommended airspace. That's one advantage to having separate chambers.