I measured the Audeze iSine10s using a G.R.A.S. Model RA0045 (with a Model 43AG ear/cheek simulator for isolation measurements), a Clio 10 FW audio analyzer, and a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most of these measurements, I used a Musical Fidelity V-Can headphone amplifier and the analog cable because, like most audio analyzers, the Clio needs to use its own test signals for most measurements, and I currently have no way to send those signals through a Lightning connection. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.
The iSine10s’ frequency response with a passive connection was flatter than that of most earphones I’ve measured, and more like that of typical planar-magnetic over-ear headphones. Their upper-midrange response peak (a characteristic found in most good headphones) is centered on the unusually low frequency of 1.5kHz; usually, this peak is centered somewhere between 2 and 4kHz.
This chart shows how the iSine10s’ measured response changes when the Cipher cable is used. (This measurement was taken with pink noise, with the EQ in the iOS app at its default setting of Flat.) A large peak is introduced at 3kHz, and the mid-treble region is elevated by 8 to 12dB. The blue curve shows my best attempt at matching the response with the Cipher cable to the passive response. This difference is intentional; Audeze says it uses the DSP in the Cipher cable so that the iSine10s’ response will better match the responses of the company’s open-back, over-ear headphone models.
This chart shows the results of 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. It shows that the iSine10’s response is, for all intents and purposes, unaffected by the output impedance of the source device.
This chart shows the iSine10s’ measured right-channel frequency response compared with two high-quality earphone models I’ve previously tested: Audiofly’s AF1128 and PSB’s M4U 4. Just out of curiosity, I also included the response curve of Audeze’s LCD-X over-ear headphones. It’s interesting to see how close the iSine10s’ response without DSP is to the LCD-Xes’; the only major difference is that the iSine10s’ upper-midrange response peak is centered at 1.5kHz instead of the LCD-Xes’ 2.5kHz. The bass and treble peaks in the M4U 4s’ curve reflect a response more like that of most earphones I’ve measured.
The spectral-decay (waterfall) chart shows a little bit of resonance at 1.2kHz, but this is at about -20dB and dies out quickly, in about 5ms. Those extremely narrow, low-level resonances between 5 and 10kHz are common in planar-magnetic headphones, though they’re usually at lower, more readily audible frequencies.
The total harmonic distortion (THD) of the iSine10s was the lowest I can recall measuring. Even at extremely loud levels, there was no audible distortion.
In this chart, the sound-pressure level (SPL) of external noise is 75dB; the numbers below that indicate the degree of attenuation of outside sounds. For comparison, I’ve included the isolation plots of the Audiofly AF1128 high-end earphones with over-ear cable routing, NAD Viso HP20 conventional earphones, and Bose’s noise-canceling QC20 earphones. Because of their unique open-back design, the iSine10s offer the least isolation of any earphones I’ve measured; they’ll let through almost all of the sounds around you.
The iSine10s’ impedance is dead flat at 16 ohms (same as the specification), and its electrical phase is as flat as it gets.
The sensitivity of the iSine10s, measured between 300Hz and 3kHz with a 1mW signal calculated for the specified impedance of 16 ohms, is 106.7dB. That’s above average, meaning that the iSine10s will play loudly from practically any source device -- although their lack of isolation from external sounds could mean that they’ll sometimes need to play a lot louder than usual.
. . . Brent Butterworth
brentb@soundstagenetwork.com