I measured the HiFiMan HE1000s using a G.R.A.S. Model 43AG ear/cheek simulator, a Clio 10 FW audio analyzer, a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface, and a Musical Fidelity V-Can headphone amplifier. I moved the headphones around to several different locations on the ear/cheek simulator to find the one that produced the most bass and the most characteristic response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
This chart shows the HE1000s’ frequency response, which is flat up to 1.5kHz, and rises sharply above that from 2 to 9kHz.
Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp has no audible effect on the HE1000s’ frequency response.
This chart compares the HE1000s (blue trace) with HiFiMan’s HE560s (red trace) and Audeze’s LCD-3s (green trace). The HE1000s have a similar response to the HE560s, with about 5dB more energy between 5 and 9kHz, and a little more bass to help balance out that treble peak. The LCD-3s have much less treble energy above 2.5kHz, and a flatter measured response, than either HiFiMan model. Note that, unlike with most speakers, a flat measured response in headphones does not necessarily equate with a flat perceived response.
The HE1000s’ waterfall plot may not look very clean at first glance, but if you look close you’ll see that all those little blue streaks are resonances of very narrow bandwidth about -40dB below the test signal. The only resonance shown here that might be audible is the combination of two adjacent -20dB resonances near 5kHz.
The total harmonic distortion (THD) of the HE1000s is well below audible levels, even at the extremely high level of 100dBA, measured with pink noise.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate attenuation of outside sounds. As is almost always the case with open-back headphones, the HiFiMan HE1000s provide essentially no noise isolation; any sounds from outside them will come right through.
The impedance magnitude of the HE1000s is nearly dead flat at 37 ohms; the impedance phase, too, is nearly flat.
The sensitivity of the HE1000s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified impedance of 35 ohms, is 88.1dB. Although that’s relatively low, as I say in the review, it was enough for me to get a fairly comfortable volume level from my smartphone.
. . . Brent Butterworth