I measured the Everest Elite 700s 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. I moved the headphones around to several different locations on the ear/cheek simulator to find the one with the most bass and the most characteristic response. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed. However, I did run a TruNote auto-EQ sweep (see review for details) to optimize the response of the Everest 700s for the ear/cheek simulator. For all measurements, I used a cabled connection; adding a Bluetooth transmitter introduces latency and thus requires gating, which introduces anomalies into the measuring.
This chart shows the Everest Elite 700s’ frequency response with noise canceling (NC) on. The results are fairly typical, although with a somewhat stronger peak at 3kHz than I’m used to seeing. (This may be an anomaly caused by TruNote’s attempt to calibrate itself for the G.R.A.S. 43AG’s metal cheek plate, fake rubber ear, and unnaturally round simulated ear canal.) The match between the left and right channels is the best I could achieve. I can’t be sure if this is the result of minor differences in the fit of the two earpieces on the ear/cheek simulator, or if the internal acoustics of the two earpieces are different (a phenomenon I’ve seen before in NC headphones, caused by the varying amounts of space occupied by the internal electronics).
This chart shows the frequency response of the Everest Elite 700s with NC on and with the headphones powered completely off. Obviously, the tonal balance is very different in the two modes; the JBLs have very little bass in passive mode, so best not to let the battery run down.
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 effect in NC mode. In passive mode, the balance will get subtly more trebly with higher-impedance sources.
This chart compares the Everest Elite 700s with three other noise-canceling headphones -- the Bose QC25s, the Definitive Technology Symphony 1s, and the PSB M4U 2s -- all with NC on. The main difference between the JBLs and the others is the larger peak at 3kHz. Most headphones have such a peak somewhere in that octave of audio, but how big the peak should be remains a matter of debate (and, as noted above, it’s possible the peak is the result of the TruNote auto EQ slightly miscalibrating itself for the nonhuman characteristics of the test gear). The Everest Elite 700s also have less deep bass than the others, but considering that music seldom has much content below 30Hz, you probably wouldn’t notice that.
The Everest Elite 700s’ waterfall plot (shown here with NC on) is exceptionally clean in the bass, with much less resonance than I see with most headphones. There are a few ultra-high-Q resonances -- at about 6, 8, 12, and 16kHz -- but considering that they’re so narrow, so low in level (-40dB), and so high in frequency, I’d be surprised if anyone can hear them.
The total harmonic distortion (THD) of the Everest Elite 700s, shown here with NC on, is insignificant at the loud level of 90dBA, but the extremely loud level of 100dBA (which I include more for testing purposes than for any sort of real-world evaluation) pushes the internal amp or the driver over the limit, resulting in considerable distortion below 2kHz. But, as I always say, if you listen long at this volume, you won’t be hearing much of anything after a while.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. I recently did some acoustical measurements of the cabins of jet airliners in flight, and found that most of the noise is between 100 and 1200Hz. In this band, the Everest Elite 700s are roughly the equal of the PSB M4U 2s -- but, as usual, both are handily beat by the Bose QC25s.
As often occurs with active headphones, the impedance of the Everest Elite 700s was greater than 1000 ohms in NC mode and thus immeasurable on my Clio analyzer. In passive mode the impedance is largely flat, averaging about 24 ohms and presenting an essentially flat phase response.
The sensitivity of the Everest Elite 700s, measured between 300Hz and 3kHz with a 1mW signal calculated for 32 ohms impedance (my default when measuring active headphones), is 97.2dB in passive mode and 103.6dB in active mode (NC on). Thus, the JBL Everest Elite 700s, unlike many noise-canceling headphones, still produce a decent amount of volume when their internal battery runs down.
. . . Brent Butterworth
brentb@soundstagenetwork.com
