So it's a controversial topic... whether the "burning in" or wearing in of speakers/headphones and other audio devices is really a factor in their frequency response.
I lie on the side that certain specific models and brands of audio devices do benefit from some "burning in". Maybe it's just my ears getting used to a headset's sound... but usually after maybe 5hrs of sound they're usually a bit bassier and less bright.

So my questions to you guys are
1. Do you believe in the audio "burn in" hype?
2. For the "yes"-answers, do you think that burning in using reference material containing heavily different frequency content can result in a different sound signature (that is, the let's say two of the same speaker, one burned in with something very bright with little bass and another with something bass-heavy)

Any other thoughts? I think it's an interesting concept. The logical part of the "burn in" concept lies in that it seems to make sense that the materials and components are going to sound different after they've worn in, moved around a bit after being in the factory - tested, even?

New speakers need "break in" or "burn in".  I have an Eminence EPS-15C speaker.  It needed some break in.  Connecting it to a stereo system and playing music for 48 straight hours really helped.  I also have an Eminence TT-12 speaker.  New its really great for use with a Telecaster but after the stereo "break in"  it has mellowed out and is now great for what it was originally designed - pedal steel guitar.
 
"Telonics", a company that makes some specialized boutique steel guitar amps and accessories, sells basically the Eminence EPS-15C and Eminence EPS-12C speakers with their brand name that are "pre broken in".
 
 

The manual that came with my Focals said to burn them in for a certain amount of hours. It may have opened them up some. I can't really remember.

At work we use horn drivers to test microphones at very high SPL Levels (+150dB SPL) and we noticed after some time that the 2nd order distortion would get worse on the speakers. So, as opposed to the frequency response changing (which we did NOT see), I believe it's the linearity. Second-order distortion warms things up, right? I believe that's what burning in does.