If a horn is short, it will not load down to as low a frequency as a longer horn of the same shape. If its mouth area is small, then it won't have as good pattern control as a larger horn.

Beaming is another name for collapsing directivity and it occurs when a direct radiator becomes directional because of path length differences between points along its cross-section and listening points out in the environment. It occurs in a curved wall horn because wall angle gets narrower further down the throat.

I might suggest for you to study horn theory and learn how things work. The concepts are pretty simple so you can pick it up pretty quickly.