Yes, at last, my results:
To be as close to unbiased (actually for a truer AB testing) as possible, I didn't not listen to other headphones, did not went thru big altitude changes (to save my eardrum from any excessive stretchings, of course other than the ones caused by 555's), and didn't wash inside my ears and put the cotton sticks for cleaning earwax, the headband was fixed and I always put the headphones to the same exact position everytime (OK, I'm cutting the cr*p
) I think I'm being a bit, very-over-detailed-hyercritical..
I did pink noise burn/break-in for 30mins/2mins break by the burninwavegenerator and constant pink noise (flac) running at the background thru winamp, if I don't say otherwise...
(' = hours, '' = minutes)
right out of the box: raw, like cheap (even the high-priced) philips cans.
30' : better quality, closer to high-end cans.
52' 10'' : no bass impact (it literally vanished)
62' 30'' : details increased, no bass impact whatsoever still, piercing/shrill highs, soundstage did not improved so far.
84' 10'' (pink noise thru wavegenerator) + 12' 40'' brown noise thru winamp + 11' bass heavy subwoofer test tracks : sound stage is huge now, very good (wow!) bass impact compared to what it was right out of the box, deeper bass extension, excellent details, and NOW no mercy for low quality tracks (below 192kps), mellow mids, powerful highs (still quite piercing).
98' 10'' pink noise + 26' 40'' brown noise + 11' bass : piercing highs still and I even checked the EQ if I've messed some frequencies up or not by mistake, but the full soundstage just forgives the highs, bass impact has slightly (so little) decreased but still it's punchy and not muddy.
104' pink noise + 32' 40'' brown noise + 11' bass : nice overall, soundstage brings tears into my eyes when I listen to the most romantic songs for me; bass impact, quality and extent is good, details are marvellous and the highs are not too tiresome...
I think I won't continue breaking the 555's in any longer as I might not distinguish any changes and lead a whole bunch of you in head-fi to wrong directions; because the burn in process does not seem to change the characteristics any more audible after this point and I want to break them in naturally by listening to and enjoying my music. Along the way, I hope they get better and reach the optimal sound quality they are capable of giving..
I started thinking, and have a question for experienced ones out there:
Did the bass-heavy tracks stretched and tightened the coils, or the mere pink noise? And if I had followed other pathways and methods of burning in, would the sound of this broken-in 555's be much different or not? (Who knows, eh?) If I do other things to compensate, can I reverse the effects of already-done break-in and change the characteristics of the headphones to different ones (and maybe the optimum and the best sound quality these cans can give to me)
OK, I know I ask A LOT from life.. But forgive me please
Other thoughts on the HD555's:
The cable is better than e.g. the hd280pros' coiled one.
This s*cker (actually I love my 555's, I'm not offending them really) must be amplified. Lovely to my ears if coupled with my Little Dot MK III.