Most of full range drivers have incline frequency response. And with a backloaded horn implementation they have a dip in lower midrange that causes dry and bright sound. To compensate it front horn should be added.
A good example is AER big transparent horn.
I don't have experience for adding super tweeters to full range. But with compression driver horns - 4th order crossover works 1000 times better vs 1st order crossover!!! Much less high midrange distortion, sound smoother more detailed, bigger and deeper soundstage, better clarity and separation. You can follow over interpretation more easy and enjoy music. I always used forward firing super tweeter and I did alignment for both 1st and 4rd order crossover implementations.
A good example is AER big transparent horn.
I don't have experience for adding super tweeters to full range. But with compression driver horns - 4th order crossover works 1000 times better vs 1st order crossover!!! Much less high midrange distortion, sound smoother more detailed, bigger and deeper soundstage, better clarity and separation. You can follow over interpretation more easy and enjoy music. I always used forward firing super tweeter and I did alignment for both 1st and 4rd order crossover implementations.