For a quick good time, blankets...

@acman3 That's the problem with science, danger lurks everywhere.

I think the most overlooked "room treatment " is the area front/between the speakers on the ceiling. Try the blanket treatment, especially if they are standard height, e.g. 8', etc., and near field listening arrangement. Helped my room to sound a tad warmer.

Planar dipole speakers benefit more from diffusion behind them than absorption, assuming they can be 5' or more in front of the wall behind them. That allows them to create the very deep and huge sound stage of which they are capable.

I recall being at a gathering of audiophiles at the home of an audio reviewer. We were well acquainted with the excellent acoustics of the room in which many of the items that he reviewed were auditioned and all of us were surprised at how poorly everything sounded during our session.  The host had generously replaced the hard surfaced chairs on which we normally sat with a beautiful upholstered couch.  We finally realized that the only change to the room was the replacement of the chairs with the couch.  Together, we removed the couch, and voila !!  After listening for an hour or so, we replaced the sofa in the room and everything turned to crap !  I wouldn't have believed it if I hadn't been there !  Of course, the couch never was returned to the listening room.

@terraplane8bob,
Interesting! Any chance you can recall the size of the room, and any treatments?

Thank you,
Tom