Torq’s Headphone Measurement Rig & Practices
Headphone measurements that I post in threads here and in reviews on headphone.com are performed using a miniDSP EARS measurement rig. The headphones under test are driven from an RME ADI-2 DAC fs using the macOS version of “Room EQ Wizard” (REW).
Measurements are taken using a calibration of 84 dB @ 300 Hz (sometimes at 1 kHz also) - this level should be taken into consideration in the context of Equal Loudness Contours - as our perception of frequency response changes with volume level and the differences are significant enough to change the apparent tonality of a headphone with changes in listening level.
Note: Measurements performed on different rigs are not directly comparable, though comparisons to other miniDSP EARS’ derived measurements should be close enough to be useful.
Isolation
In order to minimize external influences this is mounted on a custom isolation base and within a custom isolation cell. The isolation cell is designed to minimize/eliminate any reflections from the backs of the headphones being tested back to the microphones as well as to attenuate/eliminate external noise factors.
Positioning & Clamping
The positioning of a headphone on the measurement rig can significantly affect the results, so to help alleviate this, posted measurements are the average of five different placements of the headphone on the stand.
For each placement, measurements are performed both free-standing - i.e. with only the natural tension/clamp/geometry of the ear-cups to the rig and gently clamped (via low-tension elastic bands to avoid unnecessarily compressing pads and changing the normal volume of the ear-cup).
Compensations & Curves
In the past I only simply posted the microphone-calibrated, but otherwise uncompensated (no headphone-curve) Frequency Response curves. These are done using the “RAW” calibration profile supplied by miniDSP.
Going forward I will also post Frequency plots using both the miniDSP-supplied “HEQ” (headphone) compensation profile and a custom compensation profile of my own. The custom profile is intended to show something that’s closer to what I actually hear while listening than I find with the supplied “HEQ” compensation.