Thanks for the insight Sankar.
The volume of space in the enclosure should be more or less?
Depends on the subwoofer. I will explain with an example bro.
For Pioneer TS-W3002D2 is 12" Dual 2 ohm Champion PRO Series Car Subwoofer which is rated at 1000w RMS. The subwoofer's optimum sealed enclosure box size recommended is 0.8 cubic feet. Ported enclosure size optimum recommended is 1.2 cubic feet
But for Rockford Fosgate T1D212 which is 12" Dual 2 ohm Power T1 Series Car Subwoofer is rated onlt at 800w RMS. The subwoofer's optimum sealed enclosure box size recommended is 1.25 cubic feet. Ported enclosure size optimum recommended is 1.75 cubic feet. In fact RF sub is rated 200w lower than Pioneer sub but still needs a larger enclosure to perform as per manufacturer recommendations.
Subwoofer's enclosure box size solely depends on the subwoofer and as such it will perform to it's best when fitted to a box made exactly as per manufacturer recommendations which is why company fitted sub with enclosure in most times performs better to same sub in a custom box.
Regards,
Sankar