As I've been getting to know my new center channel speaker, I observed a pretty noticeable resonance on certain female vocals and even some voices in movie soundtracks. To try to get to the source of this, I did A/B comparisons with my LS6's and not a hint of these resonances. This made me suspect that it was an enclosure resonance and not a room interaction. To check this, I moved the JTR out to the center of the room elevated about 2-3 feet and aimed into the kitchen/dining area. While I don't mean to suggest that this would remove the room interaction factor completely, I would expect a much reduced resonance if it were only a room interaction. What I heard wasn't different enough to convince me.
So being the curious guy that I am, I decided to open up the speaker and check out the cabinet construction and damping. The cabinet was overall constructed very well, although there was an approximately 1/16" gap between the cabinet bracing and the enclosure wall on one end of both braces. This seemed to be the result of not cutting the braces square. Second, the main enclosure walls were only damped with a single piece of foam directly behind each woofer - a little sparse IMO. The midrange sub-enclosure was sealed and damped with a layer of fiberglass along the sides.
The DIYer in me decided to experiment with adding extra cabinet damping. I started by putting a thin layer of Acousta-Stuf down along the back wall of the midrange sub-enclosure. Then I lined the walls of the main enclosure directly behind the woofers with about 2". Putting it all back together, I played the same tracks on which I had previously noticed the resonances. Not a hint of it was there! The extra helping of mid/upper bass that I had previously noticed was reduced as well....Overall, I'd say this was a very worthwhile experiment.
Sorry, forgot to take a picture after I finished lining the enclosure.