Tuesday, September 26, 2017

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I measured the Torque t402v headphones 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. Measurements were calibrated for ear reference point (ERP), roughly the point in space where the center axis of your eardrum would intersect with your palm if you pressed your hand against your earlobe. 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. In measurements of the headphones with the on-ear earpad, I used the G.R.A.S. 43AG’s clamping mechanism to ensure a good seal. This was a “flat” measurement; no diffuse-field or free-field compensation curve was employed.

Frequency response

This chart shows the t402v’s frequency response with the over-ear pad in the four different sound modes. The traces are color-coded to the modes: yellow for yellow mode, blue for blue mode, etc. With all modes, there’s a fairly large midrange dip between 400Hz and 1.5kHz, and the peak between 5kHz and 8kHz is stronger than the peak at 3kHz. With most headphones, the 3kHz peak is stronger. Yellow mode measured as being a lot more bassy than the other modes.

Frequency response

This chart shows the frequency response with the on-ear pad, again color-coded by mode. This is a much more typical response than I measured with the over-ear pad, with a mild midrange dip centered at 750Hz and a moderate (for headphones) peak at 3kHz. The magnitude of the measured differences among the modes was less with the on-ear pad.

Frequency response

Adding 70 ohms to the V-Can’s 5-ohm output impedance to simulate the effects of using a typical low-quality headphone amp had little effect on the t402v. This result is normalized at 1kHz, per my standard procedure. A tiny peak in the impedance produced a slight and probably inaudible boost centered at 1.1kHz, but otherwise the impedance change in the source had no effect on the frequency response.

Frequency response

This chart compares the t402v with on-ear pad in black mode (dark blue trace) and over-ear pad in black mode (light blue) with NAD’s Viso HP50 over-ear model (red) and Beyerdynamic’s tunable Custom One Pro with its tuning level in position 2 “linear” (green). The HP50 obviously had the flattest response of the three; in on-ear and over-ear modes, the t402v was bassier than the other two.

Waterfall

The t402v’s waterfall plot is very clean, with much less resonance than I usually see in headphones of this type. You can see a mild resonance at that impedance peak centered at 1.1kHz, but because it’s well damped, it dies out almost immediately. The measurement shown was taken with the over-ear pad; the result with the on-ear pad was even cleaner.

THD

The t402v’s total harmonic distortion (THD) was moderate with the on-ear pad, but higher with the over-ear pad because of the headphone’s lower sensitivity with the latter pad. In the above chart, results with the on-ear pad are shown in the dark traces, at 90dBA (dark green) and 100dBA (dark orange); results with the over-ear pad are shown in the light traces, at 90dBA (light green) and 100dBA (light orange). With the on-ear pad, the THD is fairly typical: at 90dBA, 1% at 100Hz and 3% at 20Hz, those numbers respectively rising to 2% and 7% at the very loud listening level of 100dBA. With the over-ear pad, the results at 90dBA (still quite a loud level) were similar to the 100dBA results with the on-ear pad, but at 100dBA the distortion was pretty high. However, it’s unlikely that you could reach such high levels with the over-ear pads installed if you’re driving these headphones with a phone or tablet.

Isolation

In this chart, the level of external noise is 75dB SPL; the numbers below that indicate the attenuation of outside sounds. The green trace shows the t402v’s isolation with the on-ear pad, the purple trace the result with the over-ear pad. These results are typical for passive on-ear and over-ear headphones; you’ll get very little reduction of level in sounds below 1kHz.

Impedance

The t402v’s impedance is essentially flat, averaging 18 ohms, with very moderate phase shift. As noted above, the Torque’s impedance does have a slight peak centered at 1.1kHz.

The sensitivity of the t402v, measured between 300Hz and 3kHz with a 1mW signal and calculated for the rated 16-ohm impedance in black mode, was 101.6dB with the on-ear pad and 93.9dB with the over-ear pad. The on-ear results are typical for closed-back headphones, but the over-ear results are low -- more like what I’d expect to measure from audiophile-oriented planar-magnetic headphones.

. . . Brent Butterworth
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