Based on Dr. Griffin's paper I think it should be possible to do this allthough it will be in far field. According to Dr. Griffin's paper, four 6.5 driver should go far field at approx 6 ft @ 2KHz and then the beam should start to diverge. two 5 inch long ribbons on 6 inch centers, with acceptable vertical dispertion angle of 10 deg. included, should provide an acceptable vert. winddow at 12+ ft.

What have I done wrong? Four higher quality mid/bass drivers and two ribbon tweeter might be a littel less expencive and easer to build than a 10 driver 6ft array. Granted it would be Farfield, but it's all about tradeoffs is it not?

My short 4 stack "arrays" tend to sound like a point source in far field. The good thing is the efficiency is better than the single driver. They did not use ribbons. Try making a 16 driver array with the PE $.67 drivers to get the nearfield sound. You may like it and then save up for more of the better drivers. You will have a closer idea of the tradeoffs you are making.

-Linc