The biggest cons with planar magnetic headphones have traditionally been price (very expensive), weight (comfort) and external amplification, which on average needs to be quite substantial because planar magnetic drivers tend to be power hungry. Hifiman has solved these historical disadvantages of planar magnetic headphones with the Sundara, which doesn't require solid-state amplification to deliver the level of detail planar magnetic headphones are known for. On top of that, the Sundara manages to keep the sound lively without "over-toning" the bass like dynamic drivers typically do.

The Hifiman Sundara you see pictured, it's the 2020 revision version, which is a step up from the HE400 series, in terms of sound and construction. While the Hifiman Sundara 2020 revision look similar to the newly released HE400SE Stealth Magnets version, the Sundara 2020 revision is on a league of its own when it comes to craftsmanship. The Sundara 2020 revision have a premium build with metal being used for 90% of the construction of the headphone. This includes the earcup housing and grille mesh, which are made of black anodized aluminium metal.

The Hifiman Sundara 2020 revision retain the same ratchet style headband adjustment as the HE400SE, which consists of a flat headband yoke made of anodized aluminium and tiny grooves for adjusting the headband incrementally. The metal dual band on top measures 2.5cm wide and sits suspended overhead the headband strap, which is made of thick protein leather with smooth textured finish on top and a rough finish on the bottom. The headband strap is a 4-5mm thick and has no foam padding.
The Hifiman Sundara 2020 revision planar magnetic drivers have high sensitivity (94dB) and low impedance (37 ohms), which means you can get a decent volume level when driving the Sundara 2020 revision headphones from a portable device like a smartphone or digital audio player (dap). That said, you will certainly want to pair the Sundara 2020 revision with an external dac/amp or a powerful dap to improve the experience. The Sundara 2020 revision magnetic drivers deliver a "clinical" and dissected sound that reveals micro details. This means, you can hear more frequencies across the bass, midrange and treble range, including upper treble and sub-bass. Out of the box, the Sundara 2020 revision headphones are a little on the "bright" side but, there is a lot of wiggle room to EQ them so, you can turn up the low end and turn down the high end for a tighter bass.

There is no mention on the user guide whether the earpads can be detached from the earcups but, you can actually remove the Sundara 2020 revision earpads and replace them with after market earpads. The stock earpads can be rotated around the earcups too, which lets you adjust the beveled side of the earpads. This is useful if your head is kinda of odd shaped. 

Being beveled, the earpad foam padding is narrower at the bottom (1.5cm) and wider at the top (2.5cm), which effectively allows the Sundara 2020 revision headphones to sit on the ears more naturally at a downward angle. Additionally, the earcups can also tilt up and down, which in turn causes less pressure around the ear, making the Hifiman Sundara 2020 revision much more comfortable to wear. Despite the metal construction, the Sundara 2020 revision headphones weigh just 385 grams, which is 5 grams lighter than the HE400SE stealth version. The included cable weighs 33 grams.

The total thickness of the Sundara 2020 revision earcups (including the ear pads), it's 4cm, which means the Hifiman Sundara 2020 revision headphones have a slim profile similar to the Deva planar headphones. In fact, in terms of earpad design and construction both the Sundara 2020 revision and Deva are very similar. The earpads are made of protein leather with honeycomb pattern fabric material sewn on the front side of the earpad. There is also holle perforations around the inner hole, which helps air flow. Overall, the Deva headphones are more of a hybrid, featuring the same headband style as the HE400SE. The Deva headphones come also with a wireless adapter, which turn the Deva headphones into wireless planar headphones - the first of its kind.

The Sundara 2020 revision planar magnetic drivers are housed inside a 10cm diameter metal housing, while the grille mesh is 8cm in diameter. The grille mesh makes the Sundara 2020 revision standout from other Hifiman planar because the open-back grille mesh is designed like a microphone grille with a woven wire mesh and a close-knit fabric mesh to protect the drivers from dirt. The Deva and HE400SE earcups, in the other hand, have a perforated metal open-back, which doesn't look as aesthetically pleasing as the Sundara's grille mesh. The woven mesh also allows better airflow into the drivers, and widens the stereo separation.

The outer diameter of the Sundara 2020 revision earpads measures 10cm, while the inner hole diameter measures 6cm, which is a bigger hole opening than the Hifiman headphones mentioned earlier.  The depth to the driver is 2.5cm. Compared to the newly released HE400SE Stealth Magnets planar headphones, the Sundara 2020 revision headphone is noticeably much louder, which is interesting because the sensitivity between the two is almost the same. 

The Sundara 2020 revision has 94dB sensitivity output, while the HE400SE Stealth has 91dB. A few reasons why the Sundara 2020 revision sounds louder and crispier than the HE400SE Stealth include the open back construction of the earcups, better quality audio cable and the driver design. The Sundara 2020 revision uses an extremely thin diaphragm (2 microns thick).

The Sundara's metal dual band overhead is built-in to a plastic body, which houses the metal headband yoke. The headband strap measures 6cm wide and looks like it is a suspension headband but, it isn't. The headband strap is just like the HE400i, which is fixed in place; hence it does not self-adjust.

The Hifiman Sundara 2020 revision comes with a thick premium 1.5 meter long audio cable, which features a rubber sleeve, crystalline copper wire and 3.5mm gold plated connectors. On one end of the cable, there is a right angle square plug which is thick and made of aluminum metal. The other end of the cable has a hard plastic y-splitter with dual sided plugs made of plastic and rubber strain reliefs. The y-split of the cable measures 43cm long, which is very long and there is no cable cinch. This means, when wearing the headphones the y-splitter will dangle just above the navel (belly button). The Hifiman Sundara headphones come packaged inside a pre-formed insert, which is lined with satin-like fabric material. You can buy the Hifiman Sundara 2020 revision from Hifiman or Amazon.