It's definitely not normal, let Rhydon have a look at it.
The Magnum v4 drivers are well behaved, they should be smoother (/less sibilant) than most Grado's.
I don't think it would be caused by the Turbulent Labs cups. The two companies have a collaboration going on and they are aware of each other's product which should go pretty well together.
Edited by devouringone3 - 11/24/12 at 4:29am