peterinvan
1000+ Head-Fier
When a headphone has sibilance it is never because of its cable. It is because of bad or non perfect tuning in high frequencies. Cables cannot and will not affect the frequency response of the headphone. And sibilance will not go away without corrections to the frequency response. You can instead experiment with denser foams or other kind of materials between the transducer and the ears but experimenting with cables is a total waste of time and money. Different cables is only marketing, empty of reality and audio science. The best solution is always a different headphone or EQing. Never count on cables!
My 109s did not settle down till about 200 hours of break in. The drivers need time to acheive optimum flexibility before you try any other tweaks.