Jean-Michel Le Cléac'h made a breakthrough in acoustic horn design by simulating the wavefront propogation for the desired parameters.  He explains it here: diyaudio

Le Cléac'h horns provide a linear load to the driver and are known for creating a deep and natural soundscape.

I make 1200, 1100, 550, 425, 340, 204 and 160 Hertz horns to order for diy projects, with throat sizes and flanges to suit your needs.

I present my own horn system for anyone to copy or improvise around. It includes a new passive two way 'subtractive' 1st order capacitorless crossover: the iixo  or Impedance Inverter Crossover.

Thanks for visiting,

Martin Seddon
Perth, Western Australia.

Dear Martin,
Your package arrived safely yesterday.
The horns look absolutely exquisite.  Your attention to the smallest details is  evident. You have made me a beautiful product - thank you!
Thank you too for the drawings of the base: will be easy to construct for me.
Regards,
James

Jean-Michel Le Cléac'h (1954 - 2013).  "Oui, nous perdons un collègue d'une grande gentillesse, d'une grande disponibilité, d'une grande compétence, une des âmes de notre musée."