charts?

even class A amps waste more than 70% of the power just to keep them properly biased and in class A opertation. What matters is the actual power delivered to the headphone which is given by     E X I cos(x) where cos(x) is the power factor which makes life bad for EE guys.   Long live...

JackonStone: An output impedance of 4-8 ohms means that the amp can drive headphones which have an impedance of 4-8 ohms and higher. Although if we treat headphones as DC resistances you can work out that the current demand will be very high. More current means more heat and heat brings...

The whole idea is to run things in their comfort zone, for an amp output impedance 600 Ohm driving a 600 Ohm headphone is a full workout for the amp, its a nice idea to have some headroom for the amp to run smoothly.

---> http://www.head-fi.org/wiki/headphone-impedance

--> http://www.head-fi.org/wiki/headphone-impedance

---> http://www.head-fi.org/wiki/headphone-impedance  

This is a simpler and practical expression and takes in a lot of assumptions, one could go onto more depth but then it wont be useful for the people who don't have an EE background. I kept it short for this reason only.

exactly, the drivers as from my past experiments do not change in characteristics. None, of the electrical properties apart from weakening of the magnetic field strength (which takes a LOT of time to be significant) everything remains same. Especially when modern drivers are sealed  with...

please note:   I stated it in terms of speed of electrons, it is not! speed of electrons in a conductor is constant, rather the potential that they are accelerated under changes

the increased weight explains the base response changing too you know

it can be the dried out ear pads recovering

Fact is, ask any cable manufacturer to test his product with an O'scope and plot charts within the 20-20k range, you will be surprised.   I believe there should be standards in audio equipment. Manufacturers should have their equipment tested and rated accordingly using measurable...

--> http://www.head-fi.org/wiki/hi-end-cables

10101010101010101010   That's it! simple, on or off, 1 or 0, 0v or +5v. Only if it were so simple, we presume that digital signals are "clean" 1's and 0's sadly they are not. When things are happening so fast (a few megahertz) things can go crazy inside a cable. Inductance, interference, jitter...