To update on that, what Iâve found with continued use is that they need a good 24h to get clearly better than the HE-400i and justify the extra expense and inconvenience, but at that stage theyâre better in everything except dynamics; for dynamics theyâre about the same.
Not so once you go up to weeks of energizing. I canât say how long I had left them on because I wasnât keeping track, I just hooked them up and kept postponing the listening session, mustâve been 1-2 weeks total. New eye-widening experience this time: better dynamics and 3D-ness/body/realism to the instruments, at a level Iâd never heard before. And they didnât require warmup playback first, they were doing this right off the bat. Again Nottagorilla was right that we should keep these energized for as long as we can, and they just get better and better for many days after plug-in.
Nope, nope, nope. Further experimentation proved that I was mistaking playback (membrane movement) effects for simply keeping them powered up. Keeping them powered but inert does nothing for the sound, all of the improvement is from the cumulative playback time since last power-on, something along these lines:
1h - theyâre no better than the HE-400i
3h - much better dynamics and detail of mids and highs than the 400i, realistic/holographic presentation of the stage-central vocals/instruments, but none of the bass depth or punch Iâve come to expect
4.5h - bass is filling in now in terms of extension but still has no punch
7.5-8h - bass is extended and punchy now (punchy like an open-back not like a closed-back ofc).
So it looks like after every unplug, these require something like a âwarm-up dayâ of 8h playback before theyâre performing at their best, and then they donât seem to lose much of it by staying powered but not playing for a couple more days. Judge them earlier than 8h of warm-up and you might as well be listening to a different headphone.