I measured the Sphears using a G.R.A.S. Model RA0045 ear 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 used one of the supplied silicone eartips because it fit the RA0045 best, and because I used silicone tips for most of my listening. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The frequency response of the Sphears has a somewhat higher ratio of mid-treble (6-10kHz) to lower treble (ca 3kHz). Most earphones I’ve measured have a more prominent peak around 3kHz, and less energy above that. There’s a little less bass than I often see, but the more reserved 3kHz peak subjectively balanced that out.
Adding 70 ohms of output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp has no significant effect, boosting bass by less than 1dB at 20Hz.
Here the Sphears (blue trace) seem to have a tonal balance similar to that of the Sony XBA-H1s (red trace). The RBH EP3s exhibit substantially more bass, but also a lot stronger output between 2.6 and 6.5kHz, which is probably why I found them to sound brighter than the other two.
The Sphears have a very clean spectral decay (waterfall) plot, with no noteworthy resonances.
The total harmonic distortion (THD) of the Sphears is almost nonexistent, even at the very high signal levels I use for this test. This low distortion may be part of what made their sound so unfatiguing.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The Sphears’ isolation is weaker than I’d expected, given their exceptional fit -- but, of course, they fit my ears differently than they fit the simulator.
The Sphears’ impedance is almost perfectly flat in phase and amplitude throughout the audioband.
The sensitivity of the Sphears, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 16 ohms impedance, is 104.1dB. This confirms what I found in my listening: that they delivered satisfying volume levels from any source device.
. . . Brent Butterworth