The Philips SHE3580 already sound fantastic out of box. If you want an even smoother sound, there is an old trick: add a resistor, about 22 to 75 ohm. Such a resistor can suppress resonance and damp peaks. Give it a try, if you can solder.
I'm using 75 ohm. I might try some other values later, but so far the sound is smooth like silk, very satisfied.
PS: I changed the resistors to lower values and I fully wrapped the adapter. Both the sound and look are now perfect. If you want to try such an adapter, I'll make one and mail it to you after you donate $20 or more: Donate with PayPal or Donate with card.