Actually, I was just thinking upon looking at the driver of the T50RP:
The high frequency ringing could be a product of the way the driver is mounted. The actual moving element of the driver is held in place behind a plastic grid, and thus will always be several mm away from being 'flush' with the baffle.
As I understand from designing speakers, not flush mounting a tweeter is generally a bad idea because it will produce interactions between the edges of the baffle and the sound waves - leading to dips and roughness to the treble.
According to my speaker design handbook, they generally stopped using wave plates / phase discs in front of tweeters because they can produce cavity resonances and a 'tizziness' to the sound.
This effect is probably even worse on the T50RP driver considering the giant grid in front of the driver introduces many many edges.
Some interesting measurements taken in this post on the effect of surface mounting a tweeter:
Edited by a_recording - 9/3/13 at 5:51am