My thoughts here are that one must be careful that one is not being confused by a positive impact of isolation materials in conflict with how the system has been 'tuned' to have a certain sound. I have always found viscoelastic materials - eg, sorbothane - and Blu Tack positive in effect - but I have never adjusted the level of "sparkle" in other ways, beforehand. If someone was listening, over my shoulder, to a system I was opimising then halfway through the exercise they would be shaking their heads - the sound could be very sharp, bright, "in your face" ... "How can you live with this?" they might say. I would grin, and say, "We're not done yet. I've got the level of detail up to where you can hear everything, but now you can also hear all the distortion artifacts remaining - which are very unpleasant!". The next round is to kill all those artifacts, and the isolation materials play a part in that - and what then remains is the 'pure' sound of just the recording.
