The fibrefill dissipates the heat from compression, and since the subs are still compressing air inside the box, it should act the same way. keep in mind that the volume of the cone will now be added to the box volume, so the box is slightly larger(really should not make a big difference).

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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