Here's what Dave posted at AVS:
http://www.avsforum.com/t/849859/the...#post_23788215
Several things have changed in the Sierra-2 since our initial discussion regarding RAAL 70-20 Sierra-1 vs. Sierra-2. As things stand now, it is difficult to say which is actually the better speaker, much depends on the application. The 70-20xr ribbon tweeter is the overall "better" tweeter, but in this application, I am not sure anyone could actually hear that difference.