Summary

Use of OpenScad to design a vented port (a hollow cylinder) as a pipe to be inserted with x screws on a speaker audio box, at front or side of the box, adding a bass reflex feature. Then the audio box will gain or boost in low frequencies.

IMPORTANT !! The design is based upon the web "https://subbox.pro/en/"
This is a subwoofer box web based calculator.
Given the dimensions of the box, characteristics of the speaker drive, etc... the web app calculates the bass reflex pipe needed.

Variable parameters for the pipe will be :

• height of pipe
• thickness of the pipe
• pipe external diameter
• width of the support-ring
• pull-out-of-the-pipe (pootp), a portion of the pipe visible outside
• number of holes for the screws
  (pull-out-of-the-pipe must not be 0, as we need the ring thickness stronger enough supporting the pipe by the x screws distributed around the ring)

The web app calculates the length of pipe (included the thickness of pootp)
So, finally, this will be the variable "height" to use on the code.

The file .stl published here is a piece with the following dimensions:
Length of pipe: 89 mm (including 3 mm of depth of pootp)
External diameter of the ring where the screws are mounted : 49 mm
Number of holes for the screws: 5 (suitable for wood, length according to needs, with 2.5 mm diameter of thread and 4.8 mm diameter of head countersunk type)
Internal diameter of the pipe : 30 mm (parameter important for the audio box calculator software)
Thickness of the pipe: 2.5 mm
As a consequence of the preceding two dimensions, the external diameter of the pipe : 35 mm (same diameter of the hole to make on the audio box)
Obviously, by editing the .scad file you can obtain the desired dimensions.
But on this .scad file, the diameters of the holes where screws will be inserted are still considered as work in progress, as they are still not parametrized, instead, some concrete values were used to create the .stl file.
To take into account and to be implemented for the next revision of the .scad file.