Based on our past experience, there was a definite need for a speaker system that handles more power at mid and high frequencies. The McIntosh electronics section was making higher power amplifiers and we didn't have a speaker that would handle it. Multiple tweeters can be used to increase power handling, but using several tweeters that cover the same frequency range is normally a bad thing to do. Then the column is not vertically directional, except beyond the floor and ceiling where output is not wanted. The near field is extended by the cylindrical radiation pattern.
Horizontal dispersion is, of course, wide.
This column arrangement is also referred to as a line source or line array. This kept the center to center distance as small as possible. The width was selected to support the lowest frequency required of the domes. A column of 25 could just be fitted between the floor and ceiling of our listening room. The tweeters were wired in series-parallel.