I want to show you how I find the volume of the rear speakers.They have a complex form and the introduction of data in the appropriate program will take a long time, after assembling of the cabinet i do additional processing and here the math does not help. From waste material I made this gadget ,that takes part in the measurements and when assembling the cabinet: I prepared the two shells in this way; I fill the cabinet with water to the red line / there ends the front panel with the speakers /. I find the volume - 43l, I deduct the weight of the internal ribbed - massa 3.4kg. And the net volume of the cabinet is 39. 6l. More than I need, I need about 32l. The problem is that my investor likes the vision of the column.The decrease in volume must occur inside the construction of the cabinet.This sends the project in a more initial phase,we have a new requirement for the project, second W18 EX001.