kiwiplant wrote:Anyone know what all this impedance stuff is about?
Well, in the quotes you copy - rubbish.
kiwiplant wrote:"They are very difficult to pair with other gear as they are reactive due mainly perhaps to their lack of efficiency but also perhaps due their impedance. You would definitely get better performance with a headphone amp designed to drive them."
Higher quality equipment is often less efficient; this is a result of damping resonances and suchlike. This impedance is mid-range, and will be handled by any general-purpose headphone amp (i.e "one designed to drive them"!). Note that some headphone amps are intended for portable use with low-impedance headphones of high sensitivity designed for use with battery-driven devices, and so may not be able to provide the drive required.
"Even though rated at 62ohms, they seemed to be be requiring more power than the average headphone with the same load impedance."
Impedance is not a measure of sensitivity. All this comment and the previous one are saying is that a sufficiently powerful amp is required - this is hardly surprising.
"My personal experience with the AKG K701 is that it sounds best when driven by an output impedance between 62 to 68 ohms, for example."
Power amplifiers are expected to have an output impedance of a fraction of an ohm; a higher output impedance will damage the fidelity, as the speaker/headphone assumes a low impedance output by design. This writer is simply confused, and can be ignored.
There is nothing arcane in the design of amplifiers, whatever the golden-ear pundits would like you to think. It is (or should be) a straightforward engineering process.
Paul