headphone measurements

Every headphone recommended on this website displays a Frequency Response graph (if available) and a link to a full set of measurements that is meant to tell you how the headphone sounds and performs.

Frequency Response:

The top left graph on each of the measurement pages is the frequency response plot. You'll see two sets of response plots on this graph. The bottom grey set of measurements shows the raw measured ear drum response of the headphone. This measurement is taken five times, each time with a slightly different position on the measurement rig. The resulting ten measurements (5x2 channels) are then averaged, compensated and shown as the top two graphs.

TL;DR: Left side is wub, right side is cymbals, middle is voice; the higher the line, the louder the frequency range.

Harmonic Distortion (%THD+Noise)

An ideal headphone is reproducing a perfect signal...but that doesn't exist. In an ideal world your input is a 1Khz tone and the headphone outputs a 1Khz tone. But every headphone alters the sound to some extend and these distortions may cause some of that energy to appear at other frequencies.

The THD+noise plot sweeps a probe tone from 20Hz to 7kHz through the headphone. This probe tone will stimulate distortions, which will move some of the probe tone energy elsewhere in the frequency spectrum. The resulting signal is filtered and the the RMS amplitude of the remaining signal measured. The remaining info contains all the total harmonic distortion and noise products of the probe tone.

The two spikes at 200Hz and 2Khz are an artifact of the tester and can be ignored

TL;DR: The stuff a headphone plays back, but was never told to.