I measured the Audiofly AF140s using a G.R.A.S. 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. Measurements were calibrated for drum reference point (DRP), the equivalent of the headphones’ response at the surface of the eardrum. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed. I used the medium-size silicone tips supplied, and also tried the medium-size foam tips. There was only a slight difference in response, so except for the isolation measurement, I stuck with the silicone tips.
Compared with other earphones I’ve measured, the Audiofly AF140 has a relatively (but not grossly) strong peak at 2.5kHz, and a little bit (relatively speaking) of a dip in the mids at around 800Hz, but overall, the response looks fairly flat.
Adding 70 ohms to the V-Can’s output impedance of 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has a big effect on the AF140’s performance. While the balance of bass to treble is pretty much flat with a low-impedance (i.e., high-quality) source device, the tonal balance will radically change if a high-impedance source (e.g., a cheap smartphone, tablet, or computer) is used: the sound will become much bassier and much duller in the highs. This is due to the big impedance swing you can see elsewhere in these measurements.
This comparison of the AF140 with the NuForce Primo 8 (a multidriver, balanced-armature earphone) and the Sony XBA-H1 (a hybrid design with one dynamic and one balanced-armature driver) shows that the Audioflys’ overall tonal balance looks fairly flat; their only real anomaly is that midrange dip.
Except for a long but very low-level resonance at 4kHz and a fairly strong but brief resonance at 13kHz (which also shows up in the frequency-response curves), the AF140’s decay looks pretty clean.
The AF140s’ total harmonic distortion (THD) at 90 and 100dBA is relatively high. Granted, these are very loud levels, but most of the earphones I’ve measured produce no more than a few percent THD on these tests. Even at 90dBA, a loud but still realistic listening level, the distortion hits 3% at 800Hz. This will be very audible, given that the main distortion harmonics will be at 1.6 and 2.4kHz, where human hearing is very sensitive. At 100dBA -- a level impracticable for listening but that, in these measurements, does tend to separate great from so-so products -- the distortion hits 14% at 800Hz.
The spectrum of a 500Hz sinewave confirms that AF140s’ distortion is relatively high. Even at the loud but not crazy-loud level of 90dBA, the levels of second- and third-harmonic distortion are almost equal, at about -28dB.
In this chart, the external noise level is at an SPL of 75dB; the numbers below that indicate attenuation of outside sounds. The AF140s don’t deliver much isolation in the “jet engine” band down low, but their isolation is fantastic at higher frequencies. Between 100Hz and 1kHz, the reduction ranges from -5dB at 100Hz to -17dB at 1kHz. But look at the 4kHz result: down -45dB! So while the AF140s probably won’t do a lot to damp the drone of jet engines, they’ll definitely block much of the hissing of the ventilation system, and probably help quiet screaming kids (for you, at least).
The AF140s’ impedance curve is a wild ride. That’s not uncommon for balanced-armature earphones, but still, dropping from 74 ohms at 20Hz to 16 ohms at 11kHz is a pretty big swing. However, the impedance phase is fairly flat.
The AF140s’ average sensitivity from 300Hz to 3kHz at the rated 38 ohms measures 106.2dB -- enough to play loudly with practically any source device.
. . . Brent Butterworth
brentb@soundstagenetwork.com
