ZMF Eikon Sealed Around-Ear Headphones Measurements
Raw frequency response plots show mild changes in level with movement, but very little change in tonality. Raw frequency response is essentially linear with a warm tilt to the notch at 16kHz. The neutral target would have it gently rising from 600Hz to 1.5kHz. The concha peak at 3-4kHz is about the right height and frequency, subsequent response about right on average, but quite rough. In listening, the peak at 6kHz seemed to annoy only occasionally, but the notch from 7-9kHz did seem to reliably remove some sparkle from cymbals.
Looking at the measurements my biggest initial concern was the large feature at 1.5kHz in the frequency, impedance, and distortion response plots. I did spend some time listening to sweeps and pink noise to see if I could hear anything going on here. The only observation I could make was the slight dip in level seen in the FR when running a sweep. Otherwise, this feature appears to be benign to my ears.
30Hz square wave has a little too much shoulder and too small an initial spike indicating a warm headphone. Waveform top has good shape and is quite horizontal backing up the good bass extension of the FR plots.
300Hz square wave shows a low initial transient and a generally upward trend subsequently indicating a slight warm tilt to the treble range. This plot and the impulse response show quite a bit of noise subsequent to initial stimulus transients. Normally, I would have assumed this would be a grainy sounding cans from these plots. I didn't hear these cans as grainy. I heard them as not enunciating some things well due to the missing stuff 7-9kHz, and maybe a tad bright 5-6kHz, but not grainy. Noise seems strongly periodic and not random; CSD plots show some ridges between 5-10kHz that may be the source.
The THD+noise plot is dominated by the strong spike previously mentioned at 1.5kHz and a significant rise in the bass. I have to say the bass distortion puzzles me. Normally, you'd see some lack of bass extension and/or sway-back 30Hz square waves to go along with it. I heard the bass as a little gruff and lacking a bit of punch compared to the best, but it didn't sound loose or slow.
Impedance plots shows a nominally 330 Ohm headphone with a broad primary driver resonance at about 35Hz, and a strong resonance at 1.5kHz probably due to the tube-shaped structure behind the driver.
With broadband isolation at -26dB the Eikon seals very well against outside noise.
Needing 291mVrms to achieve 90dBspl at the ear, the Eikon may not achieve satisfactory listening levels from portable devices.