Do you know what a resonance is? Every physical object has a fundamental resonance. The Sundara and other fairly inexpensive HFM planars such as the 400, 4XX, Sundara, 5 SE, 5XX have resonance points at or above 70 Hz. This means the drivers will misbehave under 70 Hz..
I think you're conflating driver resonant frequency with resonant frequency of the entire headphone assembly, which I'm not sure is even high enough to measure. Simply, my Sundara's whole unit vibrates simply because there's not enough clamp force to dampen the vibration—and I prefer it this way.
You can look a the frequency response of any dynamic headphone to easily ascertain the resonance/center frequency of its bass, but this is not so for planar headphones. They have no such resonance centered in the bass region. It's much more likely that they have their centers much higher. In the case of the 6se, I suspect that it's pretty high. The 6se to me sounds like a large tweeter. It's large enough to produce sufficient subbass frequencies for some neutrality-oriented users. For me, and probably for many, as made obvious by the apparent rate of for-parts-only HE-6se units I've on Ebay with a dead driver, this is not the case.
As an example let's look at one of the most familiar headphones to anyone reading this - the HD-600. Let's increase the 30 Hz bass by 15 db, at ones normal listening levels, the issues that will result:
1. significant loss in dynamic headroom of almost any amp one is running at that frequency - amp distortion.
2. significant increase in harmonic distortion.
3. significant increase in IM distortion all over the place at higher frequencies.
Okay, but why are we using a dynamic driver as an example? Everyone already knows small dynamic drivers struggle to have the excursion needed to produce subbass frequencies. Regarding point #1, yes most headphone amps do not have that kind of voltage swing to accomodate 15db increase at 30hz for many bassy tracks—for most speaker amps driving headphones, however, not an issue. #2 Yes, of course the HD600 would distort like mad with any signifcant amount of power at 30hz. #3 Maybe, but at this point the harmonic distortion alone would be so awful that nothing else matters. Planars don't suffer from this physical limitation, as the measured THD of most planars reveal.
Then there is driver "Q". The ideal speaker or headphone will provide 20-400 Hz bass and the ideal behavior is described as a Q of .707. FM like radios going back over 90 years and in audio ever since make up for less capable bass via various methods. The ones that matter here are: higher Q (looser less defined bass, slower to stop, more likely to blend into other bass instruments), and elevated mid-bass and upper bass to fool the ear into thinking its real low bass.
You have misinterpreted. The HE-6 SE is much closer to an ideal (meaning matching the recording)l bass in terms of timbre, Q, ability to start and stop cleanly. It's fine to like non accurate tunings, but, realize that they are not accurate.
I occasionally sense a bit of what seems to be bass bloom from the Sundara + XLS 1502, but I'm never really sure if it's due to the driver per se, or the recordings. However, the amount of bloom is never feels excessive. As described earlier, the plucking of the strings on a double bass sounds quite warm, large and enveloping. If this is inaccurate, it's still quite tasteful to me. I've listened to quite a few live recordings of marching bands, and drum solos, and I've gotta say the
rendering of the drums sounds very, very realistic on the Sundara+XLS. That's why I say the "bloom" I occasionally hear may actually be more due to the recordings. The 6se comparatively sounds distant, much leaner and drier. There are also several others who have given their impressions on the 6se's leanness. If this is "accurate" damping, which I doubt it is, then accuracy is just...lifeless. I think it's probably overdamped, and the Sundara + 1502 sounds much more lifelike to me. I understand Q, and Qe + Qm = Qt, but I'm not sure how you came to such a confident conclusion that the 6se comes closer to the ideal Q = .707. My experience differs bigly.
Regarding how Q affect rise and fall, or "start and stop" in your words, the higher (looser) the Q, the faster the driver is actually able to rise, due to the lack of damping. A very powerful transient signal, therefore, may benefit from a high Q for the desired impact, else a low Q absorbs a lot of that initial energy, resulting in an attack that is less dynamic. This is why I find it odd that many fans of the 6se describe it as "punchy" or "slammy." My experience has been that while it's adequate for snare drums, kick drums lack both the attack energy and body on the 6se.
Honestly, I don't know which is truly more accurate. My opinion leans heavily toward the Sundara+XLS for truly realistic rendering, but you may well be correct, in which case my taste wouldn't lean toward low Q.
What do you assert this proves?
Nothing? Just contextual information I thought might be interesting to support why I think it wasn't heat that killed my 6se v1.
The EQ setting you posted in the HE-6 SE thread indicates that you like lots of bass, and the quality of it isn't as important as the quantity. Closed back bass cannons would seem to be something to investigate.
To be frank, I initially wanted to match the Harman compensation curve (the one with the +8db bass) just for the sake of it. However, your assertions about the Harman curves' purported accuracy made me question it. I much later decided that I only liked the Harman curve for the 6se because I felt the 6se lacked body/presence/impact in the bass. With my Sundara, I've no desire to match the Harman curve, which exacerbates the mic proximity effect on many vocals. The subbass boost I shared in this thread doesn't even come close to matching the Harman curve, especially after you subtract the Sundara bass roll off from it. Closed cans are definitely not to my taste. Bass-boosted headphones definitely not. On my AD1000x, HD650 and HD600, in fact, I actually attenuate their bass humps to be as close to flat as possible. I sometimes even attenuate the bass to slightly neutralize the mic proximity effect for podcasts. I do enjoy a (4-8db) subbass shelf, however, especially for films and shows. So, I do consider myself very neutrality-oriented—with a splash of
fun.
