Not sure. I will adjust until it sounds a little smoother. Sometimes it could become distracting to the point where I didn't understand what people were saying if they were talking fast. Re-Eq helps and Treb adjustments assisted as well.

Also its rare that I hear this during music with vocals. It's movies with isolated conversations.

Edit: When I listened carefully at lower volumes the "sss" was still there. Just hiding behind less amplication.

HG Cherry M80's, QS8's, VP150, and a pair of EP500's