Work in Progress!
The ‘Testing Of Headphone Responses Unit’ (TOHRU) is a stereo electret microphone rig used for acoustic measurements. Still a work in progress. Currently has a flat closed-cell foam coupler for headphone measurements.
A temporary taped-together version of the rig for testing before final assembly.
A 1kHz FFT of the Sennheiser HD650 measured by TOHRU. Distortion is below -60dB (0.1%).
An uncompensated frequency response comparison between the Monoprice Retro and Sennheiser HD650. Surprisingly flat even without compensation.
Distortion spectrum of the Monoprice Retro. Distortion dips below 0.05%. Environmental noise, rather than the rig itself, appears to be the limiting factor.
A rudimentary CSD measured on the Retro by TOHRU. Decay appears well-behaved. The 42Hz resonance appears to be a characteristic of the headphones and not the test rig, as it is not present in other measurements and instead corresponds to a distortion peak on the Retro. Either that or there is some non-obvious clipping phenomenon present.