I measured the WH-1000XM2s 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 amp. On the Model 43AG I used the original KB0065 simulated pinna for most measurements, as well as the new KB5000 pinna for some measurements, as noted. For Bluetooth-sourced measurements I used a Sony HWS-BTA2W Bluetooth transmitter to send signals from the Clio 10 FW to the headphones. These are “flat” measurements; no diffuse-field or free-field compensation curve was applied.
The WH-1000XM2s’ frequency response (shown here with a Bluetooth signal with NC on and with a cabled connection and power off) looks fairly standard, with the usual peak in the 2.5kHz range and another in the 6-8kHz range. What’s unusual is that, despite my best attempts, I got a little more left/right variance than I usually do. Also, it’s obvious that Sony didn’t put a ton of work into getting these headphones to sound good in passive mode. Although I don’t show it here, switching from a 5- to a 75-ohm source in cabled/power-off mode produced a boost of typically 4dB in the bass (depending on frequency), which means that these headphones will take on a different tone if the battery runs down and you plug them into a cheap PC laptop -- admittedly, probably a very minor concern.
This chart shows the WH-1000XM2s’ measured right-channel frequency response in Bluetooth mode with NC on, measured with the old KB0065 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna. (I’ll eventually switch to the new pinna, because it more accurately reflects the structure and pliability of the human ear, and include it here mostly for future reference rather than as something you should draw conclusions from. I intend to show both measurements in every review for at least the next year before I begin using only the new pinna.)
This chart, measured with pink noise and Clio’s FFT real-time analyzer function (necessary to capture an accurate comparison of the WH-1000XM2s’ various modes, as the Bluetooth mode introduces a latency of about 200ms), shows that the WH-1000XM2 can sound quite different depending on which mode it’s set to. Incidentally, Ambient mode, which lets in outside sounds, measures effectively the same as NC Off mode, whether the headphone is cabled or connected through Bluetooth.
This chart shows the WH-1000XM2s’ measured right-channel frequency response compared with those of three other NC headphones: the Bose QC35 (original model), the PSB M4U 2 (generally considered among the best-sounding NC headphones), and the Sennheiser HD 4.50 BTNC. The WH-1000XM2 seems pretty much in the ballpark when it comes to responses typical of NC headphones -- or headphones in general, for that matter.
The spectral decay (waterfall) chart, measured with the WH-1000XM2s in Bluetooth/NC mode, shows a spectrum of plentiful but narrow resonances between 1 and 6kHz -- a strange result for dynamic headphones, but something I often see even in the best planar-magnetic models. It doesn’t concern me.
The total harmonic distortion (THD) of the WH-1000XM2s, measured with a wired connection because the Clio 10 FW’s sine sweeps can’t accommodate Bluetooth’s latency, is somewhat on the high side in passive cabled mode, but there are unusually large peaks in distortion at 70Hz and 2kHz when NC is switched on and the level rises to the extremely high 100dBA standard I use (and which most headphones pass pretty easily). I didn’t notice the distortion when I was listening, and considering that it’s limited to two narrow bands, you probably wouldn’t, either. I speculate that DSP-based EQ inside the headphones is pushing the internal amp past its limits.
In this chart the level of external noise is 85dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. (Note that I recently switched to measuring at a level of 85dB instead of 75dB; this doesn’t change the way the isolation curves look, but an 85dB level lets me get better measurements of NC headphones, which demand a lower noise floor.) The isolation of the WH-1000XM2s is pretty good for active NC headphones; they can’t beat the industry-leading Bose, but they easily beat the AKG and Sennheiser models I compare them with here.
The WH-1000XM2s’ impedance magnitude is dead flat in powered mode with a cabled connection. With power off, there’s an impedance swing in the bass from the specified 14 ohms up to 39 ohms, as well as some phase shift in the bass, which is why in passive cabled mode you’ll be able to hear a difference in bass response if you plug the Sonys into a low-quality headphone amp such as the ones built into typical laptop PCs.
The sensitivity of the WH-1000XM2s in wired mode with power off, measured between 300Hz and 3kHz with a 1mW signal and calculated for the specified 14 ohms impedance, was 96.3dB. Wired with power on, it’s 101.7dB for the specified 46-ohm impedance in that mode. This means that the WH-1000XM2s won’t play very loud if the batteries run down, but will work just fine if you’re on an airplane with NC on and are using a cabled connection to the airplane’s in-seat entertainment system.
. . . Brent Butterworth
brentb@soundstagenetwork.com