Yes, I'd like real evidence showing a sound difference due to physical change, rather than the someone's conjecture. There are some incentives for manufacturers and sellers to suggest that there's physical burn in, even if there really isn't:
- People will be more likely to buy headphones, because they sound good enough when they demo them and they'll expect them to sound better over time.
- People will be less likely to return headphones within return periods that are offered, because they haven't reached the claimed burn-in time during that period.
- The expectation of sound improving due to burn-in will actually cause the perceived sound to improve, making people less likely to return them.
- Separate from expectation effects, people's perception will adapt to the sound of the headphones so that they sound better over time, making it less likely that they'll return them.