The Motorola KSN-1038 is the best sounding piezoelectric tweeter I've found. For that matter, it's the best sounding ten dollar tweeter I've found. Everyone is entitled to their own opinion, that's fine. But I've used lots of them and found the KSN-1038, 1041 and 1056 to be the most pleasant, both by specifications and by my ear.The KSN-1005 with its long snout is the one I never really liked. It is more efficient, but sounds noticably different. There are some others that I don't like, such as the versions that aren't horn loaded and most of the generic knock-offs. But I like the Motorola KSN-1038 and I've stuck with them for the low cost two-ways for over twenty-five years. There's just a sound that I like and a simplicity of the design that appeals to me.
There is a slight rise in both the current Alpha 8 and the Alpha 10 in the upper vocal overtone region, around the 2kHz to 4kHz octave, just before upper cutoff. That's what the 0.5mH coil is for. I find the one π and two π speakers to be very pleasant, and I've always been proud of them. But if you want to build a more expensive speaker, you can always make different choices.
As for me, I think the one π's and two π's are perfect, just the way they are. I can't think of any better set of parts that gives so much satisfaction for fifty bucks.