ErichH and I had great weather today for doing outdoor measurements of some waveguides and other stuff. Weather was great for people running their leaf-blowers and lawnmowers, too, but we managed to work around them.
First, a shot of our 21st century test setup. That's ErichH trying to hide behind the SEOS18. If you look close, you can see the chalk marks on the concrete indicating the measuring angles. The control console is a laptop computer sitting on an upturned rubbish can. We used an old Advent speaker sitting on a folding table to raise the test subjects well above ground.
Here are some curves of SEOS12, using a DE250 driver. Measured at 2m distance, about 5' off the ground.
Horizontal patterns (measured in 7.5 degree steps, 0 to 90 degree range, curves unsmoothed):
Harmonic distortion (at around 90dBSPL, 2m):
red is 2nd Harmonic, pink is 3rd, green is 4th, light blue is 5th, dark blue is total. Ripple is from ground reflection (since measuring at 2m distance)