In a collaboration with Capitol Studios, Ultimate Ears developed this custom IEM for studio engineers. The manufacturers claim that the IEM has been meticulously tuned to be flat, in order to match any type of professional recording/mixing/mastering conditions.
Since I've never measured a custom IEM before, I had to build a special jig to suit them. Now I can confidently measure any customs with an air-tight seal!
CON: Unlike what the specification states, the UERM does not cover up to 20 kHz. There is a slight channel mismatch in the lower frequency region. Its impedance characteristic varies greatly over the entire frequency spectrum- making the IEM hard to be driven effectively.
The lower the output impedance of the amp, the more high frequency retained.
ON SECOND THOUGHT #3: According to ITU's definition, a studio monitoring headphone should provide a flat diffuse-field response within very narrow tolerance limits. While the UERM shows some signs of diffuse-field in the mid frequency range, it is too far off from the reference target. Rather, its response is close to JH Audio's tuning philosophy.
ON SECOND THOUGHT #4: Is it just me, or the frequency response of the UERM really resembles that of good old Triple.Fi 10 Pro?