I received my Sundara from headphones.com a few days ago, I had some time to get a good feel for them and give some first impressions.
So, first impressions.... wow. I've owned other Hifiman planars like the 400i and 4XX before, but these are seriously impressive. Especially for the price. When I was initially comparing to my two other most used headphones, the Focal Elex and Sennheiser HD 58X, I got the impression these were a bit too bright in the treble past 10 kHz for certain recordings. However, I like to use EQ so that was easily fixed. And the little EQ I did use was only -2 dB at 7 kHz and 12.5 kHz. But even without EQ, I think these are actually on a similar level as the Focal Elex in terms of imaging, tonal balance, timbre, speed, and bass response. In fact, it beats the Elex in soundstage width and just has an overall better sense of space and clarity. Things just feel more open, it's like that planar wall of sound people talk about. The Elex still edges out in dynamics and imaging depth, hitting harder in percussive tracks and maybe doing a little better with busy recordings. But wow, I am just so impressed by the Sundara so far. It has that extended planar bass I was looking for, and with some EQ it does hit harder in the sub bass than the Elex. I was debating on whether to go with the Sundara or an LCD-2, but I am so glad I went with the Sundara. I don't know if you can get this kind of clarity with a sub $1,000 Audeze, since they tend to be a little warmer and darker. Also, I think these do vocals very well, maybe not as good as the Sennheiser HD58X and HD600, which are vocal kings in my opinion. The 58X has the advantage of being more focused with it's smaller soundstage, and has a little more natural timbre and even frequency response. But the Sundara outperforms the 58X in many other areas like clarity, detail retrieval, soudstage width, and dynamics. And I think the Sundara trades blows with the Elex, which is just amazing.
So yeah, the Sundara is a keeper!