I'd like to add to John's post with some blindtesting that was done at the NRC by Paul Barton of PSB on this "brightness" issue in 2005. Like Axiom, PSB adheres to NRC principles (as well as Paradigms and Energy among others) and I've noted that some people have referred to all of them as sounding bright over the years. Its really more an attribute which some listeners prescribe to speakers with flat FR. I don't find any of those speakers bright sounding but I understand the concern.
In testing the Stratus Gold, PSB concluded that a significant group of blind test participants found that speaker as sounding too bright compared to one that had less response in the 5khz range. As a result he redesigned the Stratus to have a dip in response around 5khz. Whether it was a sonic improvement or not I'm not sure, but sales of the Stratus have been very good for PSB.
