A brief update on an RS28A pair sent to me by Mike
We'll call them units Y and Z.
Let's just do a quick FR to see the consistency. It's done at 0.5m.
Now, some quick and dirty distortion numbers
For 1k and 1.5k there are two sets of curves. The overlay is flipped in the second of each pair.
Anyway, the gist of it is that one of these is excellent. The other is still very good, but there is a bit more low level higher order distortion. Still, I would call both of these useable to 1.3-1.5k, depending on how loud you want to play. If you're obsessive, you'll buy another one or two tweeters and find a tweeter like unit Y...
Both are great up higher. As usual, the motor structure is such that, essentially, all units test well at or above 2k.