..another generalization...
I was a silk fan for a very long time. I am a metal dome convert. I always loved the sweet sound of silk in my tweeters, but I always noticed extra sounds in the midrange (1.5k-4k). I noticed this particularly on fast piano runs, violins and high female voices. I had assumed it was an issue with all tweeters untill I started listening to metal domes. Metal domes tend (again a generalization) to have faster decay rates than silks. I believe what I was hearing was interference between the signal and the decay on silks which caused a new tone to be created for a short time. The "detail" you can get with metal domes is highly attributable to their faster decay rates. If I had my choice I would use a planar tweeter in my car (amazingly fast decay rates) but those things do not like the car audio environment =(