My experience has been that you either run a 1" exit device or forget about the top octave. Compression horns having 2" exit use 4" diameter diaphragms, so there's a lot of mass to throw around and a large area to try to limit path length distances across. There's 1.4" stuff that has a 3" diaphragm, which might be a good compromise except that it's rare. And there are other sizes too, but the common standards are for 1" and 2" throats. One exception is the TAD 4001 compression driver, which sounds real nice all the way up. But it's over $1000.00 too.