From this side it looks like the old version. The front edge of the one I have here is 15mm thickness.
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Thanks a lot. What about the back edge thickness? Then I can work out the ratio and see if itâs the same as the ratio of front to back from the photos I have 
Could any other owners of the Sundara with revised pads also measure their thickness at both the thickest and thinnest points? (Actually even if you have the old pads too, for comparison.) As the pad change has a significant effect on the frequency response of the Sundara I think itâs important and interesting to quantify the exact physical differences in the pads, especially for people thinking of buying the new pads separately to improve the sound of their headphones.
The old one should be around 23mm at the back, and 15mm at the front. Iâm not sure that helps. It really is confusing what was changed and I wish it were a bit more clear.
Thanks, and whatâs the thickness at the back on the new revised pads on your Sundara?
Also 23mm. Itâs not the back thatâs different from what I can tell.
Ok now Iâm really confused, as youâve given the same thicknesses for the old and new pads - 15mm at the front and 23mm at the back. I zoomed into the first photo I posted so the pad had a diameter of 105mm (as given on the HifiMan store) and measured the size on the screen of the front and back thickness and it does seem like they are 15mm and 23mm too. The store also said they received their pads directly from Hifiman on the 20th of August, so I would have thought they would be the new padsâŚ
Iâm afraid I canât help you there. This is something that in general is hard to tell from pictures.
The confusion continuesâŚI asked Hifiman to send me photos of the Sundara pads they sell separately, which they say are the latest versions, and they sent me this:
Now to me this looks closer to how you described the old pads. And the pads I posted photos of earlier look closer to your ones, with the pleather reaching further over around the edges towards the face of the pad than this one here.
They also sent two other photos showing the front and back sides with a measuring tape that looks like it reads 15mm and 23mm.
Front:
The thing is, Iâm no longer confident that itâs just the pads that have changed. The official word from HiFiMAN is this:
âThere is no official version 2 of the HiFiMAN Sundara. Neither the drivers nor the cups have had any changes or silent revisions to them in the past calendar year. The only changes have been a cosmetic improvement to the dust cover, as well as improvements to the pad structure to ensure reliability and longevity. There have not been any changes to the pad material.â
Hereâs my suspicion with all of this - note that this is just a hunch, I donât have any more inside info, and if anyone has additional information about this by all means post it below and Iâll revise this post:
Several years ago, there was a revision to the Sundara driver - likely to improve reliability. Fang Bian assured me in February that they hadnât done any changes to the driver in at least one calendar year. He said there may have been some structure changes to the pads - also for the sake of reliability but thatâs it.
Then, you have competing reports from reviewers about the sound, and this is where this whole thing gets a bit tricky. So far, every reviewer Iâve spoken to about this who got their review unit from a dealer all got the latest revision - meaning they got the one that you would expect to get if you bought one.
Then there are some reviewers who got their units directly from China. This is what Iâm unable to verify but⌠in some cases (not all), they measured closer to the older version. This also matches my own experience, where two units I evaluated (and measured) that came directly from China were the old version (and they also measured identically to one another so itâs not just unit variation). Contrast this with the unit I got through a dealer for my more recent review and it was clearly the newer revision, as it both sounded and measured differently.
Now I suspect that if you were to buy a Sundara directly from HiFiMAN today (or anywhere else for that matter), it would be the same revision that everyone else is getting through dealers. I canât confirm any of this, but this all just looks like a situation where some of the review/loaner units that got sent out even in the past year were pulled from old stock. This makes a certain amount of sense, especially if it doesnât seem like thereâs much of a difference between the two revisions on paper - it just looks like the same headphone - but it may have been a bit of an oversight given some of the measurable sonic differences that do exist.
In any case, all signs indicate that theyâve long since moved to the more recent revision for dealers, but there may still have been a bit of a stock delay gap for reviewers specifically, if theyâre still sending review units out from old stock. I imagine this isnât the case anymore, since itâs been so long but I canât be sure.
What I would advise for anyone looking at buying a Sundara is this - regardless of where you are in the world:
- Be careful about buying used at the moment - thatâs the most likely way to get the old version
- Buy from a reputable dealer
- Buy from somewhere with a return policy
Again, I donât think physical pad measurements are going to be as indicative as it first seemed, because any pad structure changes that have occurred may not have coincided with the older driver revision.
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See I have a different hunchâŚthat in fact the Sundara, HE4XX, HE400i and Deva all use the same (or at least very similar) drivers, and itâs the pads that are the main differentiator between them. Just take a look at Oratory1990âs measurements of them all below.
Sundara (likely original pads): https://www.dropbox.com/sh/654wxtmhlq0dhqa/AAD75QfJfKih_8QL-a1O9bESa/Hifiman%20Sundara.pdf
HE4XX: https://www.dropbox.com/sh/654wxtmhlq0dhqa/AAAB2SVYvAYTKwn44x3tcqZBa/Hifiman%20HE4XX.pdf
Deva (wired): https://www.dropbox.com/sh/654wxtmhlq0dhqa/AADPEKwIqSbIZcPdKwgHMiV1a/Hifiman%20Deva%20(wired).pdf
They all show dips and peaks in the same or very similar places, just in various amounts, and with different amounts of bass roll-off, both of which could be mostly explained by pad differences (pad seal being a major factor for bass extension of course). As you and Oratory now use the same GRAS 43AG measuring rig, I overlaid your measurement of the Sundara with the new revised pads (thin green line), with his measurement of the Deva (wired, orange line):
These are very similar frequency responses. And I donât think itâs a coincidence that it looks like the new Sundara pads and the Deva pads are the most similar of all the HifiMan pads, both having the âbulgeâ you were talking about (the pleather wrapping further around the edge to the ear-facing pad surface), and using the same materials. The only difference being the Deva padâs slightly oval shaped inner ring that is not perforated like the Sundaraâs, which could explain the minimal differences seen in the frequency responses above.
Now all this could easily be confirmed or denied, if either you, Oratory or someone else with a GRAS 43AG has several of these different models, swaps the pads between them and re-measures. Apart from your Sundaras (with revised pads), do you have any other HifiMan headphones on hand?
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I just reviewed the 400i (2020) and the Deva and they definitely werenât the same drivers.
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Okay this isnât true. HiFiMAN generally aims for a similar tuning, so if all youâre looking to compare is FR then youâll see a similarity between their lowest end models and their highest end models. This by no means indicates theyâre using the same drivers. You can even tell just by looking at the differences in impedance and sensitivity.
Sundara:
- Impedance: 37 Ohms
- Sensitivity: 94 dB
Deva:
- Impedance: 18 ohms
- Sensitivity: 93.5 dB
Moreover, they arenât all using single-sided magnetic arrays. In fact, the Devaâs driver surprisingly uses a double-sided magnetic array (unlike the Sundara), so these are very different transducers, even if they share similarities in overall tuning. I spoke with Fang Bian about this as well, and he mentioned that while we in the digital media space key in on certain parameters, like whether or not the magnetic array is single or double sided, there are a lot more parameters that go into transducer design - like diaphragm thickness, magnet strength, adhesive material and so on. These other parameters are likely also why the Deva simply doesnât perform as well as the Sundara, in spite of the fact that itâs using a double-sided array while the Sundara does not.
This means that you canât expect to throw Sundara pads on a Deva and have it sound like a Sundara, even if the FR is similar. You also canât expect an HE-400i to sound like a Sundara just by throwing Sundara pads on it.
This also kind of goes into the whole question of what else is contained in FR beyond simply tonal balance, and while I do agree that many of the things we call âtechnicalitiesâ are captured by FR, this is also likely to be much more fine-grained information than you see in the graph overlay youâve provided.
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Ok read âvery similar driversâ as âvery similarly tuned driversâ in my previous post. What I was getting at is I suspect the main difference between these headphones is due to the pads, especially considering the significant difference in FR you heard and measured from the Sundara with the original and revised pads. I think it would be interesting and fun to test this theory by swapping pads between them and re-measuring if you have several of the models on hand 
In fact, due to the similar design between the Sundara and (old) HE400i, and between the Deva and (new) HE400i, you could even do an informal blind test with them as well.
A quote from Hifimanâs founder - âEverything matters.â.
If you take two identical headphones but use different glue to assemble them they will sound different.
I donât think thereâs too much information you can draw from changing pads around.
It has been a while since I listened to the Sundara and have never heard the original HE400i, so I canât comment there.
However, between the Deva and the new HE400i, pad changes will not get close to eliminating the differences between them.
You can read my comparison here:
How do you know a pad swap wonât make a big difference unless you try? @Resolve has shown with his measurements that a pad change on the Sundaras significantly changed their sound, and Oratory1990 has measurements of several headphones showing sometimes drastic changes between pads.
The pads do influence the tuning yes, but I donât think itâs quite as simple as just swapping pads - especially across models. I have a Deva here so iâll give that a shot if I can (this could be interesting on its own). But importantly, as it relates to the Sundara, the only way to tell would be to have an old Sundara in and then pad swap to see if it is indeed just the pads. But this I canât confirm since I donât have an old revision.
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