What is Headphone Burn-In? (and how long does it take)

Recently I bought some Philips SHP5900's because a friend recommended them to me and I am very pleased with them (they are my first pair of headphones over $50 dollars). I have been looking at other pairs of headphones on Drop just because and I see people in reviews talking about "burn-in" and i'm confused about it. So i'm just here to ask what it is and how long it usually takes.

I'm of the opinion that burn-in only occurs with vacuum tubes, headphones and speakers break-in to varying degrees. Pads get softer/conform to your head, driver surrounds (for those drivers that have them) loosen up, overall a very minor change to the sound from the first minute of listening. I've stood by this rule of thumb for the odd 15 years or so... if you don't like a headphone within the first 10 hours of listening... you aren't going to like it after 100 or 1000 hours. I own over 30 pairs of headphones/earphones/iem's in a variety of styles and technologies... only a couple took longer than 10 hours to "reach their final form" and were still not a big difference from the first minute of listening.
Feb 3, 2021
It’s worth mentioning that the idea of burn in is... controversial. There are very strong opinions that insist it’s a placebo, and that “burn-in” is just someone getting used to a new headphone’s sound. The science is inconclusive, it’s mostly anecdotal evidence for or against.
Feb 3, 2021
that's a really interesting concept.
Feb 2, 2021
It depends on the particular headphone in question. It also depends on the driver, the materials used & the driver technology. There's not a cookie cutter answer to this question. I have headphones that sounded pretty good straight out of the box, others that needed about 20 hours or so & yet others that required hundreds of hours to reach their optimal sound. The bottom line is that headphones contain speakers & speakers have moving parts. Some of those parts need to loosen up over time to get to their best performance. The only way that happens is by feeding them a signal for X amount of hours. Dynamic drivers as in the Philips SHP9500 generally burn in quicker than technologies like planar magnetic but that's not always a given. I would say to give any headphone at least 60 hours before making an assessment.