Reviewed on: SoundStage! Solo, November 2022
I measured the HiFiMan Sundara Closed-Back headphones using laboratory-grade equipment: a GRAS Model 43AG ear/cheek simulator/RA0402 ear simulator with KB5000/KB5001 simulated pinnae, and an Audiomatica Clio 12 QC audio analyzer. For isolation measurements, I used a laptop computer running TrueRTA software with an M-Audio MobilePre USB audio interface. For most measurements, the headphones were amplified using a Musical Fidelity V-CAN amplifier; I used a Schiit Magnius amplifier for distortion measurements. These are “flat” measurements; no diffuse-field or free-field compensation curve was employed. If you’d like to learn more about what our measurements mean, click here.
Well, this is weird. This chart shows the Sundara Closed-Backs’ frequency response, which looks a lot more idiosyncratic than I expected. There’s a strange bump around 300Hz (the source of the extra upper-bass energy I heard), and then an unusual midrange bump centered at about 1.3kHz. There’s a lot of treble energy, although probably not enough to make these headphones sound overtly bright.
Here we can see the difference in the headphones’ response when a high-impedance (75 ohms) source is substituted for a typical low-impedance source (5 ohms). As usual with planar-magnetic headphones, there’s no significant difference, so these headphones’ response will not change significantly when you switch to a different source device.
This chart shows the Sundara Closed-Backs’ right-channel response compared with the open-back Sundaras, the Focal Celestees, and AKG K371 closed-back headphones (the K371s are one of the headphones noted for coming closest to the Harman curve). All are normalized to 94dB at 500Hz. Clearly, the Sundara Closed-Backs have more lower- and mid-midrange energy than the other headphones, more energy around 5 to 7kHz, and less energy in the 3kHz range. Frankly, I’m surprised they sound as normal as they do.
The Sundara Closed-Backs’ spectral decay—i.e., resonance plot—has the usual “hash” we see with planar-magnetic models. This doesn’t present itself as a coloration, per se, but it does seem to enhance the sense of space. Normally I might expect to see a broad hash band between 2 and 5kHz, but here, we see narrower hash bands instead, one centered at about 3.5kHz, the other spanning the range between 6 and 9kHz.
Here’s the THD vs. frequency chart, measured at 90dBA and 100dBA, both levels set with pink noise. With most planar-magnetics, these lines show near-zero distortion, but with these, we see a distortion peak that corresponds with that frequency-response anomaly around 300Hz, and more distortion peaks that correspond with the high-frequency hash bands we saw in the previous measurement.
In this chart, the external noise level is 85dB SPL (the red trace), and numbers below that indicate the degree of attenuation of outside sounds. The Sundara Closed-Backs’ isolation is more or less in the range of other closed-back models. I also included the HiFiMan HE400se headphones, so you can see how an open-back model compares.
The impedance of the Sundara Closed-Backs is essentially flat at 19 ohms, with a correspondingly flat phase response—par for the course with planar-magnetics.
Sensitivity of the Sundara Closed-Backs, calculated for 20 ohms impedance and averaged from 300Hz to 3kHz, is 93.2dB with a 1mW signal, a little lower than rated, but I do this measurement differently than the industry standard, which measures only a 500Hz tone.
Bottom line: It’s hard to ignore the Sundara Closed-Back headphones’ idiosyncratic frequency response. I liked them a lot, but I’d suggest you give them a listen yourself before you buy, if possible.
. . . Brent Butterworth
brentb@soundstagenetwork.com