They're not plastic, but white-painted wood. The profile is pretty simple, with straight walls and a termination roundover. My impetus was looking at the large amount of ripple in the off-axis response of these, along with the 2k dip. I figured the 2k dip and 1k peak is probably related to the dipole action, and some of the off-axis ripple from mouth diffraction (the basic structure of these is basically a horn). This symmetrical horn-loading will hopefully allow me quite a bit more 1k-4k output, but I'm working with the crossover still- there's an interesting anomaly in that my capacitor and the heil are not adding impedances- the heil at 6 ohms with the (current, testphase) capacitor being 8 @ 1kHz, is summing to... 10?!?!?
My more active project thread is over in the planars and exotics forum at diyaudio.com and will probably be an Enjoy The Music article eventually too, so keep an eye on those two if you want to see how this monster (the horn is 22" wide) shapes up longer-term.
