True, but you'll have to use a relatively crappy driver unless you want to go through the hassle of adapting it to flange mounting. Then there's all the damping it requires...... Still, for an inexpensive system or just experimentation......... Sure wish these and others had been available way back when I was actively building for others.

Anyway, when matching a horn to a point source driver you want the two to have at least the same effective radiating area, ergo effective horn mouth area should = the point source driver's Sd at minimum. Note that this doesn't include the WG's mouth round over as witnessed by Dr. Geddes's Summa (ignore the foam insert 'dome'): Summa

If matching to another horn, then the HF horn's area should = the lower horn's throat area at minimum as witnessed by the A7-8 VOTT.

GM