I owned a pair of Duntech Sovereigns for about ten years from the mid 80's to mid 90's. I loved the sound but I was moving around a fair amount for my job and these were NOT easy to move.
The biggest problem with John's designs is that he liked to use a first order crossover on the tweeters with a relatively low crossover frequency so it was quite easy to damage the tweeters. I think I replaced the tweeters three times while I owned them.