Not in my experience - I have been listening to my 803Diamond the whole day - crystal clear open sound.
The trick is careful system setup. And careful component selection (not necessarily expensive gear, but good quality gear) because the Diamond series is very transparent to front-end performance - more so than the previous 80xD series.
I will add that the midrange (which is very good) does not reach standard of the diamond tweeter (absolutely exceptional) or the excellent rohacell woofers. In the previous 80xD I noticed some mild chestiness on the occasional male vocalist, but not on the latest Diamond series which surprised me (because I thought this was an artefact of the FST midrange, but it turned out to be, I guess, due to the previous woofer and/or crossover design).