Type: circumaural, open-back, planar magnetic
Test sample supplied by: Signature Systems, UK distributor
Reviewed in: Hi-Fi News, June 2019
Although the cheapest of the three HIFIMAN models currently in HTL's archive, the Sundara gives little away in respect of measured performance to its siblings the Arya and Susvara. Despite having a higher impedance than the Arya - specified as 37 ohms but a little over 38 ohms in our test sample - it scores immediately by having a slightly higher voltage sensitivity of 105.7dB SPL for 1V at 1kHz, averaged for the two capsules.
Unlike the Arya and Susvara, the Sundara's uncorrected frequency response begins to droop a little at LF before the 20Hz measurement limit, but only to the tune of a few dB. Above that the response is flat in trend to 2kHz, followed by a 10dB peak at 3kHz which will contribute to neutral perceived tonal balance through the lower-treble presence band. Consequently the corrected responses are all pretty flat, although they all show a dip centred on 2kHz which may just remove a little 'life' from the Susvara's sound. Despite this the Harman PPR scores are good at 79/86 ≡ 69%/75% (L/R), and they changed only marginally in our spectacles and 'hair' leakage tests - to 81/84 ≡ 71%/74% and 79/85 ≡ 69%/74% - because the Sundara is another HIFIMAN model which shrugs off compromised earpad sealing, albeit with more curtailment of low bass output than seen in the Arya or Susvara.
HIFIMAN's use of low-loss diaphragm materials means that its time domain performance isn't as exemplary. Those ripples in the uncorrected frequency responses from about 400Hz upwards indicate the presence of diaphragm breakup resonances, and these are clear from the CSD waterfalls, even though those below 1kHz are less than fully resolved because of the measurement's constrained frequency resolution. In this respect the Arya performs better, but the Sundara is no worse than the costly Susvara. All that resonance inevitably lengthens the impulse response decays, it taking 7.3ms and 6.3ms respectively for them to fall below -40dB. Both CSD plots hint at some LF resonance, and this is confirmed by the acoustical crosstalk trace which indicates a structural mode at about 70Hz.
As we normally see with planar magnetic headphones, impedance is effectively constant across the audio frequency band and hence the Sundara is free of significant frequency response modifications when used with signal sources of finite output impedance.
Of true open-back construction, the Sundara provides negligible attenuation of external sound and provides no useful isolation from the environmental sounds of urban life.