Sound Quality
The Sundara is maybe the most neutral-tuned headphone that I’ve heard from Hifiman. When I say ‘neutral’, I’m referring both objectively as per the Harman target curve, as well as subjectively just based on how the overall balance and extension as well as how each of the frequencies is standing out from each other.
Like most good planar magnetic headphones, the Sundara has a very good bass extension easily reaching 60 Hz albeit without the accentuation that Harman suggests. The bass is quite flat and doesn’t have the typical midbass hump that warms things or makes it too wooly if done excessively. Pretty good punch despite being ever so slightly closer to the lean side than the thick one. It’s free of bloat or bloom as it transitions to the lower midrange.
Due to the flat bass and lower midrange, it is not as warm-sounding as other headphones like the HD660s or even the Focal Clear. If you prefer vocals that are forward or sweet-sounding, you will find the Sundara a little recessed there. I only think the upper midrange has a dry tone but is most notable when compared to significantly more expensive headphones such as the Audeze 2 non-fazor & Focal Clear.
The treble of the Sundara is quite good. It’s a more refined version of what the HE400se has because of the right amount of quantity and smoother presentation. I would think some people may still find it a touch too hot there due to some mild low treble peaking, but I personally did not find it troublesome even paired with the Monprice THX 887 (a bright-ish amplifier).
The soundstage is pretty ok for the price. It’s better than the HE400se, and I’d say right about the same as the 400i and 400s. Has slightly more width than the Clear as well. I have no issue with how the headphone images as well. It doesn’t have that 3 blob effect and I think it’s able to layer instruments nicely.
It’s got better dynamics than the Arya, and is quite fast sounding with good detail retrieval capabilities for the price. Perhaps the best part is it’s got an agreeable frequency response that closely matches the target curve that most people may prefer. If the bass is lacking a little for you, the headphone takes the EQ well because it’s got low distortion according to measurements I’ve seen.
Efficiency
The Sundara is pretty much like most Hifiman headphones in that it’s got a low sensitivity and impedance. It interestingly sounds louder than the HE400se on portable players yet sounds more gimped. A good solid-state amplifier should easily help in making the Sundara shine.
Quick comparisons
Hifiman HE400s and 400i: The 400s is warmer and smoother but quite a bit too much that it sounds a touch muffled yet also more grainy in the treble. 400i is more similar to the Sundara but it has some shrillness, more recessed upper mids, and less punchy. The Sundara handily trumps both.
Sennheiser HD660s: The 660s is warmer and smoother (more pleasing mids and cleaner treble), right about the same technical performance. Sundara has better bass extension (maybe slams harder?), seemingly faster because of more linear bass, mids & more treble. The HD660s is a more relaxed but still accurate listen.
Focal Clear: The Clear has more similarities than I imagined. Warmer, more forward vocals, more dynamic and punchy. Better for lower-volume listening. Splitting hairs but I thought the Clear has smoother and lesser treble quantity. Better texturization of midrange tones but can be too forward depending on the track but the Sundara has a bigger stage with more distinct layering. More open sounding. More energetic top end while being slightly more tizzy as well which gives the impression of more detail. The Sundar is the soft spot for me when it comes to bright headphones.
Hifiman Arya: I prefer the Sundara on the Monoprice 887, but the Arya scales much better on higher-end gear. On the 887, the Arya is brighter, has a more coarse treble texture which can be quite annoying. More recessed midrange tone and somewhat lesser punchy bass though better extension. But the Arya sounds more open & bigger (more tall and wide) and layers much better than the already impressive Sundara. It is noticeably less congested for some tracks as well.
Conclusion
Overall, I enjoyed my time with the Hifiman Sundara. It is an articulate & lively sounding headphone that’s got an agreeable frequency response tuning that I think many people will like. If you want a touch more bass, a quick EQ fixes it and balances out the tonal balance even further.
If you’re gonna be getting this, it is imperative that you invest in a good DAC/amp combo to let this headphone sing more. And you don’t have to worry as any good entry-level ones such as the Magni/Modi 3 pair would be more than enough for it.
Just like what I said about the HD660s, the Sundara can be that one headphone that can satisfy your high-fidelity cravings if you can somehow avoid the urge of upgraditis as you progress in the hobby. At $349, it’s a good performer and one that ticks a lot of boxes.