Hifiman Sundara Review (headphone)

[0RF30]

Here's a weird one. My amp (Nait 5si) actually inverts the polarity when I use the headphone jack (i.e. the left and right headphone speakers flip from when coming out of the speakers). Should I A) do nothing, it doesn't matter if stereo recordings are flipped, B) switch my R and L headphone cords?

Not sure I understand the situatuion correctly, but A) Yuck ! (pretty cool when the stage/image of a recording you know well is flipped... again, yuck !).
Just flip the left and right cords, so B. Sounds like a faulty cable. Maybe try an other heradphone or cable, could be a faulty amp port soldering (in this case, C, I'll return the amp).

 

[Oranges]

Not sure I understand the situatuion correctly, but A) Yuck ! (pretty cool when the stage/image of a recording you know well is flipped... again, yuck !).
Just flip the left and right cords, so B. Sounds like a faulty cable. Maybe try an other heradphone or cable, could be a faulty amp port soldering (in this case, C, I'll return the amp).

It's not the cable, it's just a known quirk of the amp (see link above, it's mentioned in the stereophile review).

 

[0RF30]

1400€ amp with inverted stereo image. Nice. I know what I'll do, but it's up to you, not sure why you're asking about something which in definitive should be your own choice. If the problem is constant and you really, really like your amp, just flip the cables. If not, return the amp.

 

[Oranges]

Thank you, I just wanted to make sure there wouldn't be any issues I'm not thinking of with flipping headphone cables. probably a dumb question!

 

[sq225917]

Inverted polarity isn't mixed up left and right channels. It's a by product of the circuit topology, not an error and has zero audible effect.

 

[Oranges]

I guess i thought that was phase...So inverted channels I guess?

 

[Jimbob54]

I guess i thought that was phase...So inverted channels I guess?

Yup. And just swap the cables at the headphone cup, no probs

 

[Bernd]

Hi, I just got my Sundaras. I used "Sweetchaos'" PEQ settings on my RME ADI DAC 2 FS and man ..... these cans sound great!

Very relaxed laid back sound, lots of detail, good sound stage and the best bass/sub-bass rumble I have experienced so far (with EQ). A superb complement to my Focal Clears. I prefer the Sundaras quite à lot to the HE4XX which are a lot of fun as well but seriously less refined - at least to my ears.

 

[Flyingmonkey]

This is a review and detailed measurements of the Hifiman Sundara planar magnetic open back headphone. It was kindly sent to me by one of their retailers, Apos Audio and costs US $349.

The Sundara looks elegant and no less so than higher up in the line from Hifiman:

View attachment 124233

The cups don't swivel. That, and being new made for slightly uncomfortable feeling around my ears. The weight is inline with other headphones in this class at 390 grams. The cup is round and has inside diameter of 59 mm and depth of 18 mm.

The included cord is short and comes with right angle connector. It has a nice (silicon?) insulator. It did not seem microphonic to me.

Note: The measurements you are about to see are preformed using standardized GRAS 45CA headphone measurement fixture. Headphone measurements require more interpretation than speaker tests and have more of a requirement for subjective testing as a result. In addition, comparison of measurements between different people performing it using different configurations requires fair bit of skill. So don't look for matching results. Focus on high level picture. Listening tests are performed using RME ADI-2 DAC and its headphone output.

Mounting the headphone on the test fixture was super easy requiring no manipulation to get left and right to match at dual frequencies.

Hifiman Sundara Measurements
As usual, we start with our stereo frequency response measurements:
View attachment 124234

I like the near compliance with preference curve form upper bass to lower treble. The former though as you can see, droops as many headphones do. The peaks above 5 kHz also exceed our target which you can better see in a relative graph:

View attachment 124235

There is a bit of shortfall around 2 kHz as well which I tend to like! No, it is not good that way but it means that once I compensate for it, it should open the sound more.

Distortion shows little unexpected other than something going on between 6 and 7 kHz:

View attachment 124236

View attachment 124237

This is much better than Hifiman Ananda:

Group delay shows the typical messiness we see in mid-frequencies which seems to have a role in (good) spatial effects:

View attachment 124238

Impedance is flat at 40 ohm meaning you need current more than voltage to drive the Sundara:
View attachment 124241

Efficiency is slightly below average:

View attachment 124242

Hifiman Sundara Listening Tests
I had been listening to my AKG K371 for a few hours before swapping it with Sundara. The difference was startling in how open and expansive the sound became with Sundara. Alas, I quickly realized there is no sub-bass being produced. And sound signature was a bit bright and over exaggerated at the top. So out came the EQ tool:

View attachment 124244

Oh wow! The transformation was dramatic. Sub-bass came into play like nobody's business. Even at lower volumes I could feel the nice vibrations in my head! The notch filter took care of the highs being exaggerated and a bit harsh. And the fine but broad filter around 2.1 kHz helped the spatial qualities improve even more. Overall tonality now was warm with tons of detail especially in string instruments. Very lovely.

As a verification, I asked my son to come over and without looking at the measurements and EQ, listen to the headphone plain and then with EQ I had built above. After about half hour of listening he said there was no sub-bass and the there was something missing in the sound. With EQ he found the sound to be much improved causing him to say he likes it. So good correlation with my findings.

Conclusions
We have had a checkered history with Hifiman so far with HE-6 performing very well and the Ananda, not so much. It is nice to discover that Sundara, despite its much lower price than either two, brings a competent implementation to the table. Objectively we miss the bass by a mile but otherwise, compliance to our target is very good. Distortion while not best in class, is kept much more under control than Ananda. Likely the smaller driver is able to be much more optimized here.

Without EQ, I would not be a buyer as I love my deep bass response and highs that are a bit more sedated. With EQ, the Sundara transforms beautifully providing excellent spatial effect with respect to instrument and channel separation while providing the deep bass response that I crave.

I am happy to give a strong recommendation to Hifiman Sundara with equalization.

------------
As always, questions, comments, recommendations, etc. are welcome.

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Hi,
I really like the way you approach your reviews... Keep up the great work!
Just one question, do you know if the set of Sundara reviewed were the 1st version or the 2020 revised version?
As I just got my set, and running them through the Hidizs s9pro I do not find they lack mid bass, or are uncomfortable. I remember those being complaints from the 1st version of these, and we're fixed in the revised version.

 

[JohnYang1997]

Hi,
I really like the way you approach your reviews... Keep up the great work!
Just one question, do you know if the set of Sundara reviewed were the 1st version or the 2020 revised version?
As I just got my set, and running them through the Hidizs s9pro I do not find they lack mid bass, or are uncomfortable. I remember those being complaints from the 1st version of these, and we're fixed in the revised version.

I think 2020 version. 2017 version has some lack of 2khz and extra 4k 8k peaks.

 

[Ken Tajalli]

Conclusions
We have had a checkered history with Hifiman so far with HE-6 performing very well and the Ananda, not so much. It is nice to discover that Sundara, despite its much lower price than either two, brings a competent implementation to the table. Objectively we miss the bass by a mile but otherwise, compliance to our target is very good. Distortion while not best in class, is kept much more under control than Ananda. Likely the smaller driver is able to be much more optimized here.

Without EQ, I would not be a buyer as I love my deep bass response and highs that are a bit more sedated. With EQ, the Sundara transforms beautifully providing excellent spatial effect with respect to instrument and channel separation while providing the deep bass response that I crave.

I am happy to give a strong recommendation to Hifiman Sundara with equalization.

I played about with a Hifiman HE-560 a little while ago, it is similar to Sundara and from same stable.
Reading this review, I recognize some of the issues I had too.
I developed a Mod. which corrected many issues, the up & down frequency response curve, distortions in the "shouty-ness" region and weak bass. Perhaps same could be applied to Sundara.
BE CAREFUL, REMOVE EARCUPS FIRST - CAN EASILY DAMAGE DIAPHRAGM.
The mod. was in two parts:
Used a double sided tape to stick a strip of soft leather strip to the side walls at the back of the driver, leaving suede side out.


Used half round brass bars, same width as the magnets, to stick to the back of the magnets, using double sided tape CAREFULLY!



I believe the issues with the driver were result of diffraction of sound as it passes the magnet bars sharp edges, causing peaks and troughs in frequency range and some reflection from shiny side walls.

The result was a darker upper mid, no shouty-ness and a little fuller bass.
The upper mid. issue is difraction and distortion, causing it to shout.
For what it is worth.

 

[RHO]

I played about with a Hifiman HE-560 a little while ago, it is similar to Sundara and from same stable.
Reading this review, I recognize some of the issues I had too.
I developed a Mod. which corrected many issues, the up & down frequency response curve, distortions in the "shouty-ness" region and weak bass. Perhaps same could be applied to Sundara.
BE CAREFUL, REMOVE EARCUPS FIRST - CAN EASILY DAMAGE DIAPHRAGM.
The mod. was in two parts:
Used a double sided tape to stick a strip of soft leather strip to the side walls at the back of the driver, leaving suede side out.
View attachment 152183

Used half round brass bars, same width as the magnets, to stick to the back of the magnets, using double sided tape CAREFULLY!

View attachment 152184

I believe the issues with the driver were result of diffraction of sound as it passes the magnet bars sharp edges, causing peaks and troughs in frequency range and some reflection from shiny side walls.

The result was a darker upper mid, no shouty-ness and a little fuller bass.
The upper mid. issue is difraction and distortion, causing it to shout.
For what it is worth.

Can you show us some measurements of the FR (and THD) before and after the mod?

 

[Ken Tajalli]

Can you show us some measurements of the FR (and THD) before and after the mod?

I wish I could!
Perhaps @amirm would have time one of these days to do it, I am willing to send it in - Hint Hint!

 

[RHO]

I wish I could!
Perhaps @amirm would have time one of these days to do it, I am willing to send it in - Hint Hint!

The pictures you posted are from the 560, not the Sundara, right?

 

[Ken Tajalli]

The pictures you posted are from the 560, not the Sundara, right?

Correct. I mentioned that in the post.
Since they use similar construction for drivers, I thought it may be of interest here.

 

[solderdude]

To quantify the effects of a mod one needs to measure that exact headphone without modifications (preferably not on a HATS), apply modifications and then measure again on similar conditions.

Sundara and HE560 do not measure the same even when the plots are smoothed.

Then one should realize this is an older HE560 and pre 2018 Sundara.

So when you send it in it can only be to see how it measures now and not what it was and if anything actually changed.

 

[RHO]

So when you send it in it can only be to see how it measures now and not what it was and if anything actually changed.

Yes, it seems these mods are not easily reversible and re-applied.
So it wouldn't help sending these in to get measured.

 

[Ken Tajalli]

To quantify the effects of a mod one needs to measure that exact headphone without modifications (preferably not on a HATS), apply modifications and then measure again on similar conditions.

Sundara and HE560 do not measure the same even when the plots are smoothed.

Then one should realize this is an older HE560 and pre 2018 Sundara.

So when you send it in it can only be to see how it measures now and not what it was and if anything actually changed.

In absolute terms, you are correct.
And I do realize this is a Sundara thread, so I keep it brief.
If above graph is anything to go by, one can see "house response" in those plots, sloping down from 300Hz, dip at 2kHz and so on.
The construction of drivers throughout the HE and Sundara is very similar, with minor differences, creating similar sounding, similar measuring headphones.
Assuming one Mod. works on one (IF) , I think there is a good chance it might work on the lot.
At any rate, I have my ears to measure them, and to me it worked.
Just for interest, my other ears are:
Sennheiser IE 400 Pro (EQed) & IE800S (EQed) (IEM), Ultimate ears UE900s (IEM), Sennheiser HD660S
Modified HE560s compared to HD660S sounds little brighter , less upper bass, but more lower bass, more resolving with a bigger stage.
Before the Mod. I could hardly tolerate them - screechy, bright and not much upper bass.

 

[Ken Tajalli]

A little update:
I managed to get my hands on a pair of new Sundaras.
Let me start by saying that Sundara (right off the bat) is a superior headphone to HE-560!
The sound, I could live with without any EQ, the construction is much better.
Ear cups are metal on Sundara, plastic on HE-560 , they are also thinner, which means almost no cavity behind the driver to mess with it.
The back metal panel is millimeters from the back of the drivers, as opposed to over a centimeter on HE-560.
Also everything is better made - HE-560 looks like a cheap knock-off to Sundaras.
Sundaras are more efficient too, I reckon a modern phone can drive them reasonably.
Looking at the back of the driver, it is a similar system on both headphones, but I believe the magnets on Sundaras have a thick black coating, perhaps to control air flow and resonance damping.

 

[Zensō]

A little update:
I managed to get my hands on a pair of new Sundaras.
Let me start by saying that Sundara (right off the bat) is a superior headphone to HE-560!
The sound, I could live with without any EQ, the construction is much better.
Ear cups are metal on Sundara, plastic on HE-560 , they are also thinner, which means almost no cavity behind the driver to mess with it.
The back metal panel is millimeters from the back of the drivers, as opposed to over a centimeter on HE-560.
Also everything is better made - HE-560 looks like a cheap knock-off to Sundaras.
Sundaras are more efficient too, I reckon a modern phone can drive them reasonably.
Looking at the back of the driver, it is a similar system on both headphones, but I believe the magnets on Sundaras have a thick black coating, perhaps to control air flow and resonance damping.

View attachment 152332 View attachment 152333

While the Sundara may be an upgrade from the HE-560, I have to say I’m disappointed with the build quality and QC. The first set I recently purchased had a defective headband (right side was loose and would not stay in position). I promptly returned those and the replacement set had the worst channel imbalance I’ve ever encountered in a headphone. That one went back as well. I did very much like the sound of the first set, but the lack of quality control is a shame.