Yes I have a few sets of springs. Feet of silence as well as discs of silence and a spring manufacturers setup with ebony and crystal s. I have a set of harbeth slh5 speakers. It was quite amazing how a speaker stand change made them better. The speaker stands are open and as we know with those speakers the box vibrates with the music. The also high end stands I had before the top of the stand was a full plate and the boxes didn't sound the way they were made too. In my opinion speakers are not made to sit directly on carpet for many reasons first off they are not solid in there footing set that way. The speakers have to be solid and not moving to get the correct image. Secondly the box was not designed to be set on an absorping pad. Just my thoughts.
Regards Tom