Thursday, September 21, 2017

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I measured the Susvaras 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 an Audio-gd NFB-1AMP amplifier. On the Model 43AG, I used the original KB0066 simulated pinna for most measurements as well as the new KB5000 pinna for certain measurements, as noted. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed.

Frequency response

I see nothing out of the ordinary in the Susvaras’ frequency response; it’s a lot like what I’ve measured from other open-back, planar-magnetic headphones. Although the response of the two channels doesn’t seem to match quite perfectly, headphone measurements are susceptible to slight changes in headphone position on the ear/cheek simulator. This was the best match I could get.

Frequency response

This chart shows the Susvaras’ measured right-channel frequency response, measured with the old KB0066 pinna (which I’ve used for years) and G.R.A.S.’s new KB5000 pinna, which I’ll be switching to because it more accurately reflects the structure and pliability of the human ear. I’m including this 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 switch to using only the new pinna.

Frequency response

This chart shows the results of adding 70 ohms output impedance to the NFB-1AMP’s 1-ohm output impedance, to simulate the effects of using a typical low-quality headphone amp. There’s no difference in the response. This doesn’t mean you can use a low-quality amp with the Susvaras -- they won’t play loud enough -- but it does mean you can expect good sound even with a tube headphone amp that has a high output impedance.

Frequency response

This chart shows the Susvaras’ measured right-channel frequency response compared with some other high-end, open-back headphones. The Susvaras’ response is largely similar to the others, although it appears to have the flattest response of the bunch.

Waterfall

The spectral-decay (waterfall) chart shows a lot of strong resonances across the audioband. Though this isn’t uncommon with open-back, planar-magnetic headphones, these might be the most I’ve ever measured. But there are enough of them, and they’re so well spread out, that it’s unlikely that any of them will stand out other than the multiple narrow resonances centered at 4kHz. However, those correspond with the Susvaras’ peak in response at that frequency, a characteristic observed in the measurements of most headphones.

THD

The total harmonic distortion (THD) of the Susvaras is very low at 90dBA, and at 100dBA it’s only slightly higher, in the band of 1-2kHz. Interestingly, the tiny distortion peaks seem to correspond with some of the resonances in the spectral-decay plot.

Isolation

In this chart, the external noise level is 85dB SPL; the numbers below that indicate the attenuation of outside sounds. (Note that I’ve switched to measuring at a level of 85dB instead of my previous 75dB; this doesn’t change the way the isolation curves look, but it does let me get better measurements of noise-canceling headphones, which demand a lower noise floor.) Like almost all other open-back, planar-magnetic headphones, the Susvaras offer little more isolation than draping a piece of thin fabric over your ear. But that’s OK -- if their isolation were any better, they couldn’t sound the way they do. For comparison, I’ve included the isolation charts of the NAD Viso HP50 closed-back and Bose QC25 noise-canceling headphones.

Impedance

As with most planar-magnetic headphones, the Susvaras’ impedance magnitude and phase are effectively dead flat. The measured impedance is 62.5 ohms across almost the entire audioband.

The sensitivity of the Susvaras, measured between 300Hz and 3kHz with a 1mW signal, is 80.6dB. Compare this to 86.9dB for the HE1000 V2s, 79.6dB for the classic HE6es, and about 100dB for a set of typical headphones.

. . . Brent Butterworth
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