Ok , I have done some testing with the Karlson coupler on the vifa tweeters with a noticeable difference ,more dynamic like a horn and cleaner sound able to pick out different instruments a lot better. Have done A-B test with other subjects with the same results. Getting the right size tube length and width to match up with the tweeter is trial and error. Using the 2-pi and 3-pi drivers and x-overs. using on h-290 horn with excellent results. Used with 7 foot pipe in the bass freq. So far No difference at the lower end.