You must now determine the number and size of the subs to get the most from your setup. You will have to decide how much spl you want, and for how long you want to sustain that spl level.
One or two subs in a large enclosure, with large power can hit some incredible spl levels. One look at the current spl records can validate this type of system design. Maintaining those levels of spl brings other factors into play, the main one being the heat generated by the amplifier pumping wattage into the voice coils. More coils and more cone area will greatly increase the amount of sustainable spl.
For example, our 3.4- 4.0 cubic foot example box could use a single 15, two 12s or three 10s. The three 10s will have the highest sustainable spl, you have more cone area, more motor strength and more coils to dissipate heat buildup. It is also more expensive to buy three subs than one, all this must be taken into account in the system design.
SoundQubed subs have been designed to extract max performance from moderate box volumes. The 10-inch subs work in 1.2-1.5 net cuft, 12-inch subs work in 1.8-2.5 net cuft, and 15-inch subs work in 3.0-4.5 net cuft. Use these box volumes in multiples to calculate larger usable box volumes.
These volumes do not include the driver displacement and port volume.
Remember, SoundQubed subs use the same motors and have the same excursion capability for a given series. The system output and bass extension will have the same potential regardless of sub size. The key to a loud system is to make the most out of the available space. Larger diameter subs squeezed into a small box volume will not be as loud or deep as a smaller diameter sub in the ideal volume.