Artist Matt Hope has created HornMassive, a 2-ton, 2000-watt steel and aluminum horn sound system on wheels. As far as I can tell it's mostly been used at a few raves but hopefully a mutual friend can introduce him to the guys from Konono No 1 at some point.
This massive horn reminded me instantly of the wonderful pictures of Japanese War Tubas and various acoustic location devices used during WWI and WWII to detect the noise of distant enemy planes approaching. In England, the preferred devices for this sort of enterprise were concrete sound mirrors which dotted the UK's southern coast and many of which are still standing today.
A few years back, Danish artist Lise Autogena embarked on a new project to create a pair of contemporary sound mirrors that will allow people across the English channel to converse with each other, an especially ambitious (and seemingly impossible) goal considering that Matt Hope's 2000 watt device is touted as being able to be heard 1 kilometer away.
Says Autogena in a 2001 Guardian article
"I love the fact that it's such an awkward, failed technology, which hasn't been covered up... New acoustic technology in America can isolate sounds. So when you stand at a certain point in the mirror, you'll be able to hear the voice of the person standing by the mirror in France - but only at an exact spot in the mirror. Move just a centimetre and the sound will disappear."