Pi seven internal volume


I am half way through constructing a standard pair of Pi sevens i.e. external dimensions of driver housing 17.5" x 34.25" x 9.25" making for an enternal volume of 2.36cu ft. It now appears that my driver (Altec 421A) suits a cabinet volume of 2.25 cubic feet with a (huge) port of 8.75" x 5" (HxW) and 8" long. How important is this internal volume? What effect will a slightly bigger volume have? I could always stick an extra sheet of MDF onto one of the internal walls to bring the volume down?




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