I did a
brief comparison (re-listen) of my 4 types of
cables with the HD650s.
All tests with high resolution or redbook from Meridian Explorer via Moon Blue Dragon V3 (Cu).
Fair:
Stock unbalanced from — barely shows the promise of the headphones.
Much better:
Cardas "headphone cable" 4.5m(!) (many years old) + adapter from 1/4 to 1/8", unbalanced — Musical, solid, great midrange, much better detail, treble is slightly soft, but improved over stock.
Excellent:
Cardas Clear Light 1m unbalanced 1/8" — detailed, neutral, flat, extended, solid, authoritative, revealing, excellent treble. Get lost for hours.
Superlative:
Cardas Clear 1.5m balanced w/ RSA connector — delightfully exceeds the unbalanced, in part benefitting from the RSA balanced circuitry. Entrancing, transporting, realistic, beats expectations... and look/feel great! Cardas does not oversell the Clear vs Clear Light, so for economy don't be afraid to use the Clear Light. Clear is said to have noticeable improvements but modest; I love them both.