I measured the Audeze Sines 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. In most cases, I used the G.R.A.S.’s clamping mechanism to ensure a good seal of the earpad against the simulator’s fake rubber ear. For all but one measurement, I used the standard analog cable. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The Sines’ frequency response is typical of planar-magnetic headphones, except that there’s more bass rolloff than I usually see. There’s also not a lot of energy in the upper treble, above about 6kHz. I was occasionally able to measure more bass than you see here, depending on how I positioned the headphones on the ear/cheek simulator, but this chart represents the result I got about 90% of the time.
Because my test equipment doesn’t have an Apple Lightning output, and I have no device that will convert the Clio’s S/PDIF output to Lightning, I had to compare the Sines’ performance from the digital and analog inputs using a relatively crude technique: playing pink noise from my iPod Touch through the Sines using both cables, and comparing the results using TrueRTA with 1/12th-octave smoothing. Still, my method clearly shows that the sounds via the two cables are substantially different. Using the digital cable results in considerably more bass output: +3.9dB at 50Hz. Considering that the Sines’ bass with the analog input was unaffected by changes in source impedance, my guess is that this difference reflects an intentional engineering choice to boost the bass with the digital cable.
Adding 70 ohms output impedance to the V-Can’s 5 ohms to simulate the effects of using a typical low-quality headphone amp shows that the Sines will be somewhat sensitive to source-device impedance when used with the analog cable. With the higher-impedance source, the lower-treble response is boosted by 2.8dB at 2.6kHz.
This chart shows that the Sines have a more midrange-focused sound than two other midpriced closed-back models, NAD’s Viso HP50 and Oppo Digital’s PM-3; both of these have stronger bass and upper-treble responses.
The Sines’ spectral decay (waterfall) plot shows a broad area of resonance between 1.5 and 6kHz, but these resonances drop quickly in level, and are gone within 5ms.
The total harmonic distortion (THD) of the Sines is pretty close to zip, even at extremely high listening levels.
In this chart, the level of external noise is 75dB; the numbers below that indicate the degree of attenuation of outside sounds. The Sines have about the same amount of isolation as another midpriced, closed-back headphone model, NAD’s Viso HP50.
The Sines’ impedance is flat at about 22 ohms, except for a 40-ohm peak centered at 2.5kHz. The phase response is almost entirely flat, except for a mild wrinkle that corresponds with the impedance peak.
The sensitivity of the Sines, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 20 ohms impedance, is 96.6dB -- a little low. This is enough to produce decent volume from a smartphone or tablet, but if you like to crank the sound up loud, use the digital cable or a separate headphone amp.
. . . Brent Butterworth