I don’t quite see it like that - or at least, that’s not how I experience the quality. It’s quite literally just a physicality and punchiness. Anyone who has heard a Focal headphone or one of those Fostex headphones likely knows what this quality is. In my opinion the debate around it is kind of like a “what Mary didn’t know situation”. You can learn everything there is to learn about frequency response and whatever else (all good things), but once you actually have the experience you realize there’s something more to ‘knowledge’. Now, the analogy breaks down because… I’d like to think this quality is also measurable, I just don’t know how yet in a way that would be predictable in visual terms.
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Nope, not talking about clipping. I’m talking about overshooting.
I have Focals and I know what you’re talking about.
I think I’m not explaining myself well above. Oh well 
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Actually I will mention one more thing.
On single sided planars, on the stroke away from the magnets, the magnetic field between magnet and coil gets weaker. This coupled with higher tension of the membrane and therefore higher resistance against the magnetic force and half your sinewave is compromised.
maybe one can use a pitot tube to measure displacement in air.
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Well, it’s that it’s not clearly defined what it actually is. You can say anything you like about macrodynamics. It doesn’t tell us anything because anyone can have a different interpretation about what it is. If someone can put a clear definition on it we at least know we are talking about the same thing.
Before that you cannot even start an investigation about if it exists or not. Because you have no idea what you are looking for. Maybe it’s real, maybe it’s not? Without a definition it is not, because we can be all talking about a different thing.
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That would show up in distortion measurements.
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That would show up in the FR grapth. Driver excursion is directly related to SPL. De frequencies where the driver “overshoots” (your term) is just louder.
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All well and good. But the broader suggestion that I was commenting on, which is that a failure to properly measure or define equals non existence being a baffling viewpoint still holds.
If a measurement comes out that can quantify or define something discreetly, great. Doesn’t magically change the existence of that being measured though on a macro scale. Let’s leave Heisenberg out if it. 
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This is the natural course of concept development and refinement. Ideas often start out as loose and muddled observations, or simple hunches (i.e., most of this thread on the Stealth). That’s perfectly fine. This process goes wrong when one of two things happens (1) advocates claim a rough idea is fully valid and proven, or (2) critics throw out a crude work-in-progress rather than explore further.
Precisely the opposite. This is the only possible starting point for exploratory research. Researchers walk in the dark through rooms covered with razor blades. They make mistakes but must keep trying. For “slam” we’ve seen half a dozen loose explanations above. Some are fully testable (e.g., pitot tubes to check air movement as mentioned by @antdroid just before you).
The final interpretation of natural language “slam” may combine or conflate several different technical properties and perceptual phenomena. Nothing can be determined without data
Steps for obtaining relevant and comprehensive data:
- Collect common language definitions of the loose concept. This is narrowed by the implications of “slam,” “macro,” and “dynamics” to a limited range of options. Sounds may become louder in dB, perceptually louder, undergo faster changes, involve air movement, involve skin movement, etc.
- Collect possible explanations for what could cause the word slam to be used by reviewers and hobbyists, based on nothing more than raw speculation (e.g., hardware properties, headset fit, closed cups, etc.)
- Condense #1 and #2 into a set of unique and clear summaries.
- Present the summaries as a survey to a variety of experts and experienced hobbyists to check for omissions and surface errors.
- Have experts assess whether each idea has merit per: (a) electrical changes, (b) mechanical changes, (c) psychological or physiological processing and perception, and (d) interacting factors such as specific musical structures, compression, etc. Use your imagination and give every idea the benefit of the doubt.
- Design test protocols to change hardware, content, etc. as needed.
- Conduct research studies and collect data to validate or toss each explanation.
- Generate a final definition following data analysis. Explain how each item in #3 got it right or wrong.
It’s not cheap, it’s not easy, and perhaps not worth the effort. But this is how it can and often is done.
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“Say my name!” Haha 
Sure, but those who claim this is not a real thing, as fact, can have the scientific background to make such claims.
We don’t know if there’s a teapot in an orbit around the sun. It hasn’t been investigated. But I doubt anyone would claim it’s a 50/50 chance there is. Because we haven’t investigated and so we don’t know.
From all the knowledge we have, we can conclude the chance is a good as 0.
That doesn’t mean that if someone does detect one flying around the sun and can scientifically prove it, the rest of us can’t change our mind about it.
Existing knowledge can show the chances of the concept being invalid, even if the specific concept itself has not been investigated.
I’m not saying that is the case here. I’m saying that some can conclude that some subjective qualities are not worth investigating because they have knowledge that contradicts the existence of such subjective quality. (Not me. I’m not knowledgeable enough.) But they can still be wrong. You would need to come with convincing evidence to make them change their mind.
I think we agree. You just explained it better.
What’s the Sinad of the teapot? 
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Who cares? I don’t drink tea. 
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That’s the stuff of scientific revolutions, and new or outside evidence can force one to rethink basic assumptions. At one time physicists believed in phlogiston. At one time biologists believed in the four humors.
Thanks.
Scientifically oriented people can seem dogmatic, but hey are only dogmatic if they refuse to change their mind even in light of convincing evidence.
Then there is is the issue that you need to be able to understand the evidence for or against an hypothesis. Some people just accept an hypothesis as fact, just because they lack the knowledge to understand the evidence is lacking and vise versa.
@rho you make good points. Need to think more…
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A software engineer mostly involved in marketing does not make an acoustic engineer, no matter how often they post their credentials online.
They have the same amount of scientific knowledge in the field of acoustics as other unrelated engineers.
It would be the same as saying a RMT is an expert on virology because they have scientific backgrounds.
Currently, there are no peer reviewed scientific studies to prove dynamics or spatial qualities that were exuded in another review on the internet. Nor was a volume matched, blind AB test conducted against the headphone mentioned as a comparison.
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I was not talking about one specific person.
But I think the one you are thinking about has more then just a marketing background only. That also doesn’t mean that because I agree with many thing he says, I agree with all things he says and how he says them.