An externally hosted image should be here but it was not working when we last tested it.
http://www.diyaudio.com/forums/multi-way/140190-jean-michel-lecleach-horns-79.html
The note on the first page is in French. Google translates this to
There is also a spreadsheet for the calculation of quasi cylindrical waves Le Cléac'h basshorns at http://nicolas.davidenko.perso.sfr.fr/outils/cylind.zip
notice:
This spreadsheet is for pavilions including two walls are parallel, so the expansion is done only in one plane. (You might call these flags: flags radial). Pavilion serious Mr. Roggero is a pavilion of this type. An option to use a wall of the listening room as an element of symmetry, this is what leads to the shortest pavilions extreme serious.
To reduce the file, the sheet is shipped empty of these lines of calculation. To enable the calculation of all the points, it is necessary in the sheet "Horn calculation" copy the line 34 from the line 35 up to the line 4035.
use:
The choice of parameters is made in the sheet "Horn calculation."
In case B10, choose the low cutoff frequency sound, knowing that it is desirable to electrically cut an octave above.
In case B11, enter the throat diameter or motor output, mm.
In B14, we can choose the type of expansion, one in the case of an expo, 0 for hyperbolic. The usual value for a flag of medium will be 0.707 (hypex).
In B19, we chose a coefficient that defines the type of flag, round or square. 3.14 for a round pavilion and 4 for a square.
In B37, a factor that allows the flags are used in corner of room, consider walls sides that extend the pavilion. 2 default if it ignores walls (generally) and one with the walls.
Choose the settings, let Excel calculate (a few seconds) and view the result on: Half sheet horn profile that draws the profile.