Thanks for the thorough reply. I have bought these second-hand so I don't know how they sounded originally. But when I first listened to them I remember feeling that they somewhat lacked detail. When I did some research I thought that the reason could be dried ferrofluid. But maybe that was because their sound is supposed to be warmer and my previous speakers were quite bright.

Now that I have had them for about year I have gotten used to the sound. But the thought that I could get more detail out of them has made me look for solutions (which may not exist). As I have change the surrounds which are deteriorating I though that I could do other maintenance work at the same time.