IDK about a quilt but you can get acoustic tiles made from fabric/polyester fiber that you can attach to the top of the hearth. There are also tiles that look like art work.
Flexible room treatment material???
My speakers flank a large slate-tile hearth that also houses a glassed-in propane fireplace.
Is there some sort of flexible room treatment material that could be fashioned into a "quilt" and hung from the top of the hearth to cover these hard surfaces while listening???
I’m very happy with the sound I get but can’t help but wonder whether such a strategy might yield worthwhile benefits.
My wife is handy with a sewing machine.