You can decrease the volume required for a particular sealed alignment by using a stuffing material such as fiberglass, wool, or polyfill in the cabinet. Reductions of up to 30% in volume requirements are possible. Make sure that you add the volume displaced by the driver and bracing to arrive at a final enclosure volume.
If you plan to
stuff the enclosure, use 0.75*Vb as the net volume for the enclosure. When you add
stuffing to the enclosure, the resonance frequency should decrease. Continue adding
stuffing until the resonance frequency stops