Acoustic instruments radiate sound in a wonderfully complex, 360 degree fashion, while conventional loudspeakers radiate in a much more boring, spotlight of sound. You could spend a ton of money on fancy products: Hemisphere from Electrotap Experimental Meyer Array or you could follow these instructions to build a cheap array out of IKEA salad bowls and surplus automotive speakers. It won't sound as "accurate" as those other speakers, but it's surprisingly good and looks pretty cool on stage. Special thanks and apologies to Dan Truman and the researchers at CNMAT, who's scientific work directly inspired this project. P.S. Here's another cool loudspeaker array.
http://www.instructables.com/id/Low-cost-Spherical-Speaker-Array/