Final Notes:

As with the other 1.4" Waveguides/horns the top octave dispersion is determined largely by the driver phase plug design and throat angle match-up.

This 1.4" version of the SEOS-18 is taller and lends itself to a wider vertical dispersion then the rest of the normal 90x40 SEOS waveguides.  Difficult to tell from the photos due to the gloss coating but the shape of this waveguide is more conical with smaller round-over transitions at the mouth then the smaller SEOS horns (in comparison to the overall size of the horn).  I believe this is why more waist-banding is seen in the off axis dispersion.

Speaking of which the overall dispersion is quite wide nearing 100-110 degrees horizontal between 2-8kHz though this is partly a result of a small depression directly on axis as you can see a slight bloom in the same region moving a bit off axis.  Vertical dispersion is also quite a bit wider but that is more to due with the taller aspect ratio of the horn, though some waistband still present there.

Overall quite a disappointing result in directivity uniformity for this larger SEOS horn in comparison to some of the smaller 1" options.