Lehmannaudio Black Cube Linear - Understanding Headphones; Why Use Headphones?; What Makes Headphones Different?

Lehmannaudio Manual Black Cube Linear - page 4 -
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Why headphones?
When you use headphones you can reach a very high level of sound reproduction at
a fraction of the price you would have to spend for a regular hfi setup with high
quality loudspeakers. Detail resolution and dynamics of even the best loudspeakers
can easily be reached with the best headphones. In most cases headphones will be
used to enjoy music either to acoustically disclose a noisy environment to just to be
able to listen to louder levels without disturbing other people.
What makes headphones different?
There is a number of parallels between (dynamic) headphones and loudspeakers.
Technically they are complex loads for the amplifiers driving them and should
therefore be used with stable outputs. There are headphones with higher
impedance that need a higher signal voltage and low impedance types which need
more current for optimal sonic results. Just connecting a headphone to any given
headphone output without considering the headphone’s electrical characteristics will
most likely yield dissatisfactory results.
Impedances of dynamic headphones can vary from 30 Ohms to 600 Ohms.
Transferred to loudspeakers this would result in impedances from 4 Ohms to 80
Ohms. The same signal amplitude results in a power consumption difference of
factor 20!
Loudspeakers and headphones are manufactured in a dazzling variety. Irrespective
of their impedance headphones and loudspeakers can have very different
effectivities which means that the electrical signal is converted more or less
effective to acoustic anergy. When comparing loudspeakers the dimension used is
the sound pressure level (SPL) reached at a given power of 1W (at 1m distance).
There is a similar parameter for the effectivity of headphones except for the fact
that the standard power is 1mw (=1/1000W) The figure is given as dB/mw which
means the resulting sound pressure level at 1mW (not per 1mW).