It can be square or rectangular, just needs to be expanding from the throat. Yes or I wouldn't have posted it. 
Yes, the dip isn't nearly as bad as HR predicts, but our hearing acuity isn't good enough even if it was and the 3-400 Hz dip is < +/- 3 dB which again won't be this bad in reality + is most folks threshold, so likely won't be an audible issue.
Note too that virtually all horn designs benefit from 'critically' damping its terminus to quell reflections back to the throat like at ~1 kHz, modulating the driver unless heavily rounded over or at least has a 'flip out' like the B&C horn except it needs to be greater for best performance. I ran out of time to sim this version.
Yes, the dip isn't nearly as bad as HR predicts, but our hearing acuity isn't good enough even if it was and the 3-400 Hz dip is < +/- 3 dB which again won't be this bad in reality + is most folks threshold, so likely won't be an audible issue.Note too that virtually all horn designs benefit from 'critically' damping its terminus to quell reflections back to the throat like at ~1 kHz, modulating the driver unless heavily rounded over or at least has a 'flip out' like the B&C horn except it needs to be greater for best performance. I ran out of time to sim this version.
Faital FH500 is already quite efficient. It is not suitable for horn loading. I wished I had seen this thread earlier. Look at this spec sheet, what does it say?
- 12" Mid-Bass Speaker
- Lightweight Neodymium Magnet
- Cast Aluminum Frame
- 4 or 8 Ohms
- 45Hz-4kHz
- 500 Watts AES
- 1,000 Watts Program
- 97dB SPL
- High 7.5mm Xmax
- Weighs 8.8lbs.
- Designed For Bass Reflex Front Load Cabinets <<<<<<-------------------------------------------------!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
- https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=151050100