If you mean simple and cheap, here's one. The Foster wide band drivers are $3/ea from Madisound. I used 14 midwoofers per side because I wanted these to be outrageously tall. Twelve per side wired 4-4-4 or 3-3-3-3 would probably be more practical. The midwoofers were designed for an open back application and they run full range with no crossover. The tweeter requires a simple second order crossover and some padding. Nobody will ever confuse these with high end speakers, but they do have the sensitivity, soundstage and dynamics of a line array with overall sound quality no worse than the typical two way from a big box store.
The ART Arrays sound much better to my ears. The Dayton midwoofers are much better sounding drivers than the Fosters, especially in the midrange. And being a ported design the ART Arrays have greater bass extension and much better midbass impact. The Vifa tweeter is smoother and more extended than the Eminence, which has little output above 12k. Also, the ART Arrays can be placed closer to the back wall because they're not dipoles. The tallerays need to be at least 3' from the back wall.