You feel music too, it's less important when talking headphones but still i like the low end feeling and not just hearing it.
Same. It's what I got a pair of LCD2C's for. From here on in, I'm just gonna try to exemplify the spirit of what I'm arguing over in this thread, when it comes to picking this stuff out. A lot of it is personal to me, but the arguments are in the portrayal.
Gotta be planars for the reach, even if dynamics sometimes have a bit of an edge in slap. Room for overlap on both ends but you can generally count on each for certain characteristics. Planars are better in transient overshoot than they used to be - it seems a lot of manufacturers have gone through years of trials dealing with decay and resonant frequencies in the membranes themselves. If you ever look at a CSD plot of virtually any planar, you will see at least one (usually one) sharp peak somewhere that juts deeply along the decay axis... just this dagger of driver ringing. Over time I think they've gotten better at working with the materials and applying traces. You get a lot of thinner, lighter drivers that hold up better and tend not to have that sort of 'ethereal' or 'overly fast/glossing over' quality they often had in the past - or that big, but amorphous bass. In my mind, the way that stuff functions is that the ringing interferes with the very frequency information that initially sets it off by continuing to run as the driver is asked to do more at that frequency. You lose some transient information there. What I see now is them kind of trying to place that frequency better by how they tension the driver... what tension they build it to. Maybe place it where it can be managed by airflow control or some other aspect of the enclosure. A mesh or pad can filter with some costs. Whether this stuff is heard, I can't actually say. I'm correlating changes in measurements with changes in the sounds and builds of these types of headphones over the years. Bottom line is that we get two kinds of planars now that both perform really well: warm, chunky ones with grippy bass - and cool, crisp ones with a lite but even midrange, more balanced overall. They're essentially tuning them based on the driver topology, material, and dimensions - sizing up the compromises. Irrelevant to most, I guess. I am a nerd about this stuff though.
My main consideration of the low end with the LCD2Cs happened when I was seeing the distortion measurements and quickly realizing that LCD2Cs are nearly dead flat and almost impossibly low in distortion across the whole bass range, down to the deepest sub bass. I run the signal from my Modibit into (believe it or not) a Behringer DEQ2496 in order to pump a good +5db overall bass boost where I want it. They can do much more, but on some tracks, the EQ can't - even with the input volume as low as possible, it clips the signal. The drivers in them seem like they are practically made for that... they don't do anything else exceptionally well but they can take some serious current and pump crazy amounts of bass without breaking up and I can say that I do feel it
They have quite a seal on them. Honestly, it's bordering on too much bass for normal people run at stock. These things thonk on your head and pressurize your ear cavities a little. You're in the thunderdome. It does get to that point where it's conducting well enough in your skull to rattle you. Nothing compares to the chest pound of >12" woofers, though, or vibrations coming up through your feet. That adds something completely different.
Eh... point is, I wasn't looking too much at that number, but rather sizing-up a range of factors to find that bass niche. I went to measurements more specific to what I was looking for and considered the design a bit, as a headphone can boast a fairly wide frequency response range, but not even have the full presence in those ranges when in actual use because of how the spec is applied. It's all relative to different frequencies across the spectrum. Headphones tend to have considerable fluctuations in frequency response across the audible range, and those relative amplitudes in frequencies change how everything ultimately presents itself. Nobody can tell me they haven't had a pair of headphones that had little to no NORMAL bass presence, but specced at 20hz-20khz. Maybe that same pair of headphones still manages to be dark, as well. It's a case of 'true on paper.' To me, that renders the value of it questionable in the grand scheme of purchasing decisions. It's not a foundation I would comfortably stand on. Others may choose to, and it may work for them. I'm not out to shoot anybody down. Just throwing in on my thought process.
To me, regardless of the range shown, it says the bear minimum. Even if I concede that further range = better perfoming headphone, I still need to point to the elephant that is the differing frequency responses seen across headphones as a whole. They are pretty much all distinctly colored in some way, just by concept alone. Your own damned head is a big part of the problem, honestly. All of our heads are different. And our ears, too. It ends up mattering a ton more when we are talking about trying to get a realistic sound presentation by strapping full-range-drivers-in-cups to our ears. Past a certain point in the world of headphones, it's like a high-stakes betting game on getting the right flavor of coloration. That clean, even pair just doesn't exist. Maybe you can get a pair built and tuned for your skull. Barring that, it's asking a lot to look at a spec like that and find everything you're looking for in it. For instance, that spec won't tell you what Beyerdynamic treble sounds like, or how it makes some people physically uncomfortable with its crazy treble peaks in the squeaky upper range.
I think at the end of the day, it's not about price, or some particular metric. The ears they go on ultimately decide. So in that regard, I examine many angles but hold no one true metric. I am content to rule out things that do not provide me what I deem to be sufficiently detailed info. Something that can be used to make more detailed qualitative comparisons. That keeps me from being a big believer in much of the talk about amps and dacs, either. The headphones are the bulk of it, as far as I can tell.
Actually, back to those LCD2C's for a more direct anecdote. They have a range down to single-digit hz and up to 50khz, but it really doesn't stop them from being extremely tonally lopsided. You get a flat line up to 1khz, from which point there is a steep drop bottoming at ~3khz, that only comes back up steeply when it hits the range of 5-8khz. It actually confused me when I heard it. Electric guitars really sound strange at first. Just very pulled back. It works well for terribly mixed metal, but the bite is almost detached. Vocals have similar issues. I would not use them without EQ, and even with it, they do not sound natural and suffer from some issues with imaging, detail, and timbre in the core midrange. They are simply dark and scooped. They sound big and exciting, but that's not everything a headphone can do. If all you wanted was a bass headphone, that single-digit low-end dropoff point might stand a good chance of steering you there. But if you were looking for an all-around better headphone and factoring in the 50khz side, you made a terrible mistake on an $800 pair of headphones. This is why I argue against just going by that number, or generally using this approach. It's a a good basic bar for determining a speaker's bass performance, but in the headphone world, I don't think it's a very meaningful gauge.
Take it even further back to the HD820s with their very similar 6-48000hz range. Yet they sound completely different, especially in the midrange and treble, where it's a bit like that first breath of warm air on a frozen day with how much clearer, smoother, and more present it all is. It's like a real eureka moment, they are so different. The HD820s also sound weird to me, but completely not like the LCD2Cs. The soundstage is far wider and more diffused, for instance. The 820s also won't make bass push your eyes out no matter what you do. Really completely different signatures and perks. Same frequency range, entirely different experiences.
I could go on and on. I think there is plenty of room for nuance in this stuff. There's a lot worth considering when buying headphones, depending on how serious you are about the sound. I'm not talking cables, amps, dacs, nunna that. The drivers, the enclosures that house them, the pads that support them, the damping applied when and where, the airflow. So many different ways to dial them in, all with faults. It's been a case of reinventing the wheel for a long time. There are distinct differences between all of them that are probably entirely due to the headphone's fit and general distortion/rolloff profiles. In my experience there just is no magic way to suss out the sound sans having them to yourself.