Yeah, that is some good work there. I saved the page for reference. Seems like I'm getting something around the blue 45 off axis response in the second graph. I like his comments at the bottom. Pretty much explains it all...
Comments
A well built tweeter. Quite a bit of frequency response irregularity, though interestingly, the linear distortion curves look respectable, only moderately worse than the 27TDC. Very good nonlinear distortion numbers-but some of this may be artifactually low, given the drooping FR curve. Still, even corrected for flat, the nonlinear distortion numbers look very good, much better than the high Fs would suggest. If you can at least modestly effectively contour the curve to your liking, this should be a very good tweeter. Still, it seems like alot of work!