where did you get the specs for the box? did it specify gross or net internal volume? if it's net, then you must calculate all volume displacement, eg. driver displacement, braces, port walls and port volume. If it's gross then they already calculated those things for you as long as you use their dimensions. Keep in mind that some manufacturers specify a volume with polyfill added.

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2004 300M SPECIAL
Alpine CDA 9833
Alpine Pxa-h701
Alpine Rux-c701
Rockford fosgate p400-4
Rockford fosgate p4004
Hifonics BX 1205D
JBL c608 GTi
JBL p963
Infinity 2.5" center channel
Alpine type R 12"(2)
200 amp alternator
yellow top battery
0 awg power and ground (welding cable) 300 amp anl fuse
all active SQL set up with 2000 watts rms