Just checking in - been spending most of my spare moments enjoying the cooler weather and live music streams...
Not exactly what you suggested, Wayne, but I did see some movement when trying different values in the C1 position:
Moving forward my plan is to procure a cheap piezo tweeter, to see if the rolloff is there with a completely different device with an extended range.
When time permits, I will try a first-order XO and build from there to see what each stage does to the response.
I do have a different compression driver on hand to play with, similar in efficiency to the Radians. Unfortunately I don't have mounting studs for it as they are a tad smaller than those on the Radians (but the same size as those on the DE250).