Usher Horn D-2

Yesterday i heard these horns from usher audio (they have only 1 model.
It was very impressive, here in europe we don't have many horns (i think mostly because of the large sizes), on the other hand in Japan Horns are very popular,althought the have generally smaller rooms.

Has any one set up these horns with some serious equipment? because I heard them with a cheap tube amplifier.