I measured the N60 NCs 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 clamping mechanism on the Model 43AG to ensure a good seal of the earpads against the simulator’s fake rubber pinna. This is a “flat” measurement; no diffuse-field or free-field compensation curve was employed.
The N60 NCs measure somewhat like typical audiophile open-back, over-ear headphones, with a flat response to about 1.3kHz and, above that, strongly rising upper-midrange and treble responses. This suggests that their sound will probably thrill discriminating listeners who like a fairly even response, but will grate on those who prefer lots of bass.
You can see from this chart that the N60 NCs’ frequency and tonal balances don’t vary a lot when the noise-canceling is switched off. Yes, there’s less bass, but there’s also less treble; the tonal balance should sound fairly similar either way.
Adding 70 ohms output impedance to the V-Can’s 5 ohms, to simulate the effects of using a typical low-quality headphone amp, has no significant effect on the N60 NCs, either in passive mode (shown here) or noise-canceling mode.
This chart shows that the N60 NCs are clearly voiced differently from two other well-known noise-canceling headphones, the Bose QC25s and the PSB M4U 2s. The AKGs’ response in the range between 1.3 and 4.5kHz is much stronger than either competitor, although the M4U 2s have a stronger response from 7 to 10kHz.
The N60 NCs’ spectral-decay (waterfall) plot shows a very clean response, with only extremely narrow, weak resonances at a few higher frequencies, and a much tighter (nonresonant) bass response than I’m used to seeing.
The total harmonic distortion (THD) of the N60 NCs is very low, even at the very loud levels used for this measurement. This measurement was in active mode; distortion was even lower in passive mode.
In this chart, the external noise level is 75dB SPL; the numbers below that indicate the degree of attenuation of outside sounds. The measurement of the N60 NCs’ noise-canceling mode shown here is the average of the measurements with the ear/cheek simulator’s clamp engaged and disengaged. The isolation is actually a little above average in the “jet engine band” of 50-300Hz, averaging about -20dB.
As expected, the impedance of the N60 NCs with noise canceling on (in which case the signal is routed to the amplifier input) runs above 1kHz through most of the audioband. In passive mode, it’s flat at 36 ohms up to 3.5kHz, then dips slightly, to 32 ohms, in the treble. Phase shift is negligible in both modes.
The N60 NCs’ sensitivity, measured between 300Hz and 3kHz with a 1mW signal calculated for the rated 32 ohms impedance, is 107.0dB in passive mode, 107.5dB in noise-canceling mode, making the N60 NCs one of only a few noise-canceling headphones that don’t suffer a huge reduction in volume when their batteries run down
. . . Brent Butterworth
brentb@soundstagenetwork.com
