XS has less impact and less bass under 60 Hz than the 6 SE. The XS has more midbass which is where perhaps the sense of warmth comes from.
XS has a pleasing sound to most including me but in terms of accuracy it’s not a match to the 6SE except in stage size, but doesn’t need a big amp either.
The 2 Sundara I heard were not a match for my 6SE in any way I value - what amp did/do you use with them? Our maybe our tastes are very different.
It could come down to equipment or samples but the way I heard it the XS is warmer then the Sundara.
Sundara's mids have been described to be more forward than the XS, and I absolutely love the mids on my Sundara. Warmth should add body to the mids as well, and not just be an aspect of bass. A full bodied vocal reproduction to me is much preferable, and from what I've read the XS seems to lack that characteristic.
I'm not sure if you're describing impact in terms of the impact at the same power output, or that one headphone has a higher output capacity than the other. I can guarantee you that the 6se has a lower output capacity than the Sundara...because each time I tried to push the 6se to have the same subbass output,
the drivers died.
Now, if you are describing impact at the same level output, that is very interesting...because my memory tells me that the 6se v1/2 has the crappiest bass
body of any planar I've owned, which includes: Sundara, HE-400 (og), and HE-560 (og). However, body and impact are not synonymous and body can often increase the
perception of impact. It lacks also rumble.
Let's define "impact," "rumble," and "body." To me, rumble would be how well a driver creates the sine wave at high output at subbass frequencies (<50hz). Impact refers to how well it creates high output bass transients, which is not a normal sine, but also contains higher harmonics as well. Body/presence/texture is less quantifiable to me. It's a result of how much a driver is damped. Overdamped drivers create a weightless, clinical sound, whereas underdamped drivers can be muddy, thick, and smeary. A perfectly damped system creates sound that is accurate and detailed, but without losing its "soul."
One problem with the 6se is that it is overdamped. It sounds very lean and wispy, albeit very fast, like my STAX L300. This is to its detriment, because to me it sounds clinical to the point of being inaccurate. It filters the soul out of the sound. The other problem is that it outright dies when pushed too hard, which is in hindsight isn't at all surprising. I've already done the mathematics in one of the 6se threads, and shown that it requires roughly x11 more power to drive the 6se to the same level as the Sundara. Now, most people wouldn't require more than 500mW in 98% of their listening needs from a Sundara—but I'm an abnormal person. I've gotten my Sundara to output as much as 5W when watching movies, or playing a couple tracks that have heavy bass and subbass transients, such as How to Train Your Dragon, and Infected Mushroom - Spitfire, with an EQ bass boost. I don't listen at this level for more than few minutes at a time, of course, and the EQ protects my hearing from the higher frequencies, which are exponentially more damaging to one's hearing. I've often gotten my Schiit Vali 2+ to clip when powering the Sundara...and that thing is capable of >1W per channel.
At the time that I bought the 6se, I noticed something that should've been a red flag for me: I found a number of 6se's for sale on Ebay listed as "for parts," for having a dead driver. It was pretty much only the 6se that was listed as such.
Hifiman's house sound tends toward the lean, overdamped, and the 6se is probably one of the most glaring in this regard. I'm still very, very curious of the sound of the HE-500. Everything about it that I've read tells me it might lean slightly toward underdamped, like the Audeze house sound. Unfortunately, it's still too expensive in the used market. From reading comparisons of the XS and HE-500, the 500 should have even more body than the Sundara.
