Yamaha Clavinova and Sennheiser HD518 headphones

[gyzzzmo]

After my previous headphones died (sennheiser HD448) i had to buy myself some new ones. Because of my good experience with the HD448 and good reviews of the newer HD518, i bought that last one.
But after plugging in the headphones in my Clavinova, i was quite shocked by the extremely muffled and mellow the new set gave me, compared to the HD448.

Does anybody else have experience with this combination, and/or does 'burning in' the headphones really can make such a big difference?

Thanks,

Gyzzzmo