speaker enclosure sizing

Rather than filling the tube, sound-absorbing material should be placed inside the enclosure; the tube must be free to expel air. Sound-absorbing materials are used for multiple reasons. Among many, the limitation of the reflex effect on the cone and the limitation of standing waves inside the enclosure. However, one consideration must be made: you cannot simply open an enclosure and place sound-absorbing material wherever and however much you want. In particular, if there were too much sound-absorbing material, the free volume of the enclosure would be reduced (it would become undersized compared to the previously calculated size, unless the volume occupied by the sound absorber is also taken into account). With too little sound-absorbing material, one would risk not sufficiently attenuating reflections on the cone. With material in the wrong place, accumulation phenomena could occur, especially of low frequencies. In short, designing a loudspeaker enclosure is no easy task. One must take into consideration sound-absorbing materials (there are myriad kinds), woods (there are myriad kinds), internal geometry and volume, and from an electronic point of view, one would need to understand what type of enclosure to build: a sub? A two-way mid-high? A three-way? In the case of multi-way systems, an extremely important role is played by crossovers, namely the low-pass and high-pass filters (for two-way) and the low-pass, high-pass, and band-pass filters (for three-way).

As far as I know, there should be software for the construction and dimensioning of enclosures. You should try searching on Google.

There is software for the construction of 2D and 3D Schroeder diffusers, let alone for enclosure dimensioning!

Happy building!