For those interested in the power requirements for the Stealth, the following two tables should be useful. One is based on an assumed 83 dB/mW sensitivity, the other on 86 dB/mW, since I’ve seen both numbers posts on Head-Fi, but no confirmation from Dan as to which is correct.
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Dan confirmed ~400mV @ 94 dB SPL (86dB/mW). Ill hunt down the post after breakfast
I just got my hands on a FORGE with the stock KT88s yesterday, and it seems like it’s giving my Ether 2’s more oomph where they’re typically more muted. Honestly, I’m surprisingly enjoying the pairing vs. the Rad-0 that are already inclined to slam and just go all out with the FORGE. I would be curious to hear if you have the same experience pairing the Stealth with it!
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Very cool. I have another set of Ether 2s to evaluate soon, and I think they’re with the updated pads. I’m curious to try it out on a bunch of stuff like that.
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Hi everyone! I’m sorry if this post would have been better in some other thread. I was actually going to post this at Stealth thread over at ASR but I could not set up a account there. There is a debate going on about macrodynamics of Stealth and the whole thing in general. Some people think that macrodynamics/slam/punch whatever you want to call it does not even exist because it can’t be measured. For me slam is very important for musical enjoyment. Because of that Utopia is my favorite headphone. I’ve been thinking about this alot over the years while I’ve evaluated many headphones and build some stuff myself. I’ve found some correlations between headphone designs and macrodynamics.
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Traditional dynamic headphones usually sound more impactfull than planars or electrostatic. This suggests that driver speed (transient response) is not the key here. If it were e-stats and many planars would perform better.
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Dynamic drivers that have high pistonic movement (Headhones with suspension drivers such as Focal and Fostex) slam harder. I think it’s because those type of drivers move more air.
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Dampening over the driver reduces sense of dynamics. Propably because felt or something over the drivers reduces amount of air being pushed towards ears.
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Driver size is not a major factor. I recently compared Utopia (40mm driver) and Audio-Technica ADX5000 (57mm driver) and there is notable difference in macrodynamics. It could even be that for some reason smaller drivers have an edge here. Maybe it is because more concentrated air flow.
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Increased movement of the driver might impact slam with planars too. It’s hard to tell because diaphgram thickness might play a role here too. But for some reason old Hifiman headphones slam harder than their new products. Also one planar driver manufacturer has confirmed that with his design loosening the tensioning of the diaphgram does improve bass slam.
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Frequency response is not a determining factor. Midbass boost will increase punchiness in the bass but there is more to macrodynamics than that. For example Aeon Flow Open has more pronounced midbass than Utopia but that does not make AFO’s any more lively sounding. It’s also worth noting that Focal headphones are not particularly bassy in general.
So I keep coming back to the quantity of air pushed by the driver. This is of course only a theory but I’m leaning towards the conclusion that macrodynamics/slam/punchines is either the air vibration perceived by our skin or change of air pressure between the driver and ears. It is that something extra that makes sounds more lifelike. In outside world and with speakers “hearing with skin” is definately a thing. So are the pressure changes in ear that we can perceive whether we notice it or not. I think it would actually be quite silly to believe none of that would be happening with headphones, particularly with ones that really get the air flowing.
Even if there is any truth to my specualtion I don’t know how and if measuring that phenomenon is possible. Maybe it could be done with some sort of pressure meter between the driver and dummy head and see how much changes there and how fast those changes are? I think it would be very important to determine the speed of change with the pressure. I’m again using Utopia as an example but it has this ability to slam and go from that heavy hard hitting sensation to light ethereal feeling really fast. Maybe it builds up pressure really fast and because of fast responsive driver and open housing it can dissipate that pressure fast too. If this stuff could be measured somehow it would be quite easy to compare the results between headphones that are considered to have good and poor macrodynamic performance and see if there is a correlation.
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I know that the attitude towards balanced amps is sort of lukewarm around these parts, but will you try the Stealth with a powerful balanced amp to see if it reaps any benefits? So far I only saw you using the Violectric Single Ended 
Definitely worth experimenting. I’ll be doing that too.
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Waterfall plots and impulse response graphs would be good.
Seeing this is good.
Seeing this is better.
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CSD are handier to see, especially when looking at something “peaky”.
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My only comment is that there is no comment to make. Baffling. Good first post. I’m a Utopia guy as well.
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Welcome to the forum. Nice post.
This is all consistent with my perception of slam too. Many closed dynamic headphones feel like they are slightly compressing the air in the cup with every note. For me this slowly or rapidly results in an airplane “ear popping” sensation with every beat. I almost instantly hated the Meze 99 Classics when I demoed them for causing pops.
If it’s a physical phenomenon and not auditory or [post-ear] perceptual that makes sense. The challenge is to fit an air pressure sensor akin to the in-ear tympanic membrane. Slam may follow from air physically moving ear parts (e.g., skin), and have a weak correlation with dB.
That’s exactly how the Utopia sounded to me in back-to-back comparisons with the Clear and Elex. The Elex had the same heavy hitting character as the Utopia, but it never had a light ethereal feeling. I concluded its heavier drivers couldn’t slow down once they got moving.
Claiming slam doesn’t exist…that made my jaw drop too. Even if this is a human perceptual quirk and not measurable, do people who make such claims ever listen to music instead of reading measurements?
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Well put. This is something I’ve pondered for a long time now. I come from a subwoofer and speaker background, and in those fields the word “xmax” gets thrown around a lot; xmax is the maximum excursion a driver has, and I believe it’s directly related to the voice coil. The higher the xMax, the more the driver moves; this means potentially more air being moved, which could lead to more slam or the perception of increased slam. The thing that threw me off was a conversation @Resolve had with Oratory1990 on one of the headphone shows, in which Oratory kind of debunked that theory and said slam (or the perception of) was really only related to earpad seal. I think I am remembering that correctly… Anyway, I kind of just stopped wondering about it after that and simply let my ears be the judge regarding which headphones slammed well (macrodynamics) and which didn’t.
Regarding speakers vs headphones when it comes to Macrodynamics, speakers excite room modes and cause reflections and vibrations, thus our bodies feel the bass easier. Headphones don’t really do that…
Seriously! I just roll my eyes at opinionated statements like that; or when someone says the only thing about a headphone or loudspeaker that can be trusted is the measurements, and to use a predicted scoring algorithm to determine if you’ll like a speaker or not; listening be damned! 
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I agree with most of what you said here. But I think it has to be more than just quantity of air being pushed. Because I used to own the HEDDphone, and its marketing material says it moves air 4x faster than other technologies. But my Verite slams harder than the Hedd. I think driver excursion has to be one element of the equation.
It’s an interesting quality that I’ve been investigating with some help. So far there hasn’t been any direct correlation between any measured results and this quality, because there are enough counterexamples that debunk every other result. With that said, what we’ve been able to come up with so far is that at the very least there seems to be a necessary condition for this macro contrast quality but not a sufficient one - at least insofar as it relates to planar magnetic headphones.
That necessary condition seems to be tied to both a low resonance frequency (Fs) for the driver, and minimal damping. All planars that do well for this quality (which is very few) seem to have these two things in common. There are some examples where this behavior is observed, where the headphone in question doesn’t exhibit this subjective trait, for example the HiFiMAN Arya and Ananda both seem to have this kind of driver behavior with low Fs and minimal driver damping. So it’s not enough to say “check the driver resonance frequency and Q width in free air”, but at least that does seem to be one of the few commonalities among planar headphones that do have it.
Of the planars I’ve heard, these seem to be the ones that do very well at it:
- HE-6 - Not bass boosted but still hits hard and feels lively and engaging.
- AB1266 Phi TC - This is possibly the highest Q resonance frequency I’ve ever seen, good lord. The thing is like a sheer bass peak in free air.
- LCD-4 (although I need to get a new one in to check that)
There may be others that do reasonably well at this, the Sundara comes to mind as one that’s okay there. But, there really aren’t that many planars that are outstanding in this regard like you see with certain moving coil headphones. In my experience you more commonly find that modern planars don’t exhibit this quality than do really well there.
Additionally, I’m not entirely convinced this quality is uniquely associated with bass frequencies. It seems to impact the general sense of tactility and physicality - as I said the liveliness of the headphone overall. Some that lack this ‘contrast’ quality have a somewhat softer presentation… perhaps more refined, while others have a more engaging, lively and intense presentation. It’s not better or worse, just a particular quality that’s noticeable, and as has been mentioned in this thread, some people love it and some people couldn’t care less.
I personally fall slightly towards the don’t really care side of things. My personal favorite headphone is the Susvara, even though it’s nothing special in terms of its macro contrast (the HE-6 does better there). But… for those who uniquely care about this quality, they’re better served with something from Focal, or maybe Fostex, or a ZMF headphone - or heck, check out the Borealis for that quality.
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I believe (have zero data to prove it), slam results from over-excursion of the driver. By over-excursion I don’t mean going beyond the limits of the driver, I mean going further than it’s supposed to for a given stroke. It’s basically an overshot. This coincides with @Resolve’s finding that more damped drivers (which planars tend to be) have less slam.
The only way I can think of to measure this is a computer simulation of how far the diaphragm should move for a given pulse at a given power level (you’d need to be the driver designer to have all the variables required). Then you measure the actual movement distance and compare.
How is the isolation? In and out? Decent enough? (not expecting epic levels of isolation or anything.)
If one is wearing glasses, do they clamp a bit hard, or are they a looser headphone in terms of clamp? Obviously this depends on head size, but, just sorta in general?
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As a followup, the natural response to my theory is:
“Well, if the driver is going further than it should, then everything should be louder - ie, it’s the same as turning up the volume. And since it’s all relative, where does the slam come from.”
To which my response would be that it depends. Dynamic diaphragms are heavier than planars. Let’s think about how a “heavy” (relative term), minimally damped object would move. If you push it a little (quiet signal) it’s not too hard to stop it. If you push with a lot of force (a highly dynamic tone), it’s way harder to stop it (due to its mass and inertia) and it’s easier for this mass to overshoot the point where it was supposed to stop. Therefore, everything doesn’t just get louder. The smaller signals would overshoot way less than the larger signals. And presto. You have “slam”.
You mean like… musical stroke? I kind of don’t think so if that’s the case. I suppose it depends on your reference point. If you compare sound to certain speakers, I think you might find that quality lacking on most headphones in general. And then the question becomes, are the speakers reproducing it faithfully… It’s not an argument I’d make personally but worth asking the question.
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Sure you can think of it that way. Or just think of a sinewave.
I’m going to use numbers that make for easy math and are small for the sake of this being a hp thread.
Let’s say we have a tone at 40hz. We send it through the driver at say 0.1 watt. The diaphragm moves some distance to reproduce it. We’ll call it 0.1mm. Now a dynamic passage comes along at 40hz again and it needs to be 9db louder. So the driver is fed with 0.8 watts (8X the power for 9db gain) and should theoretically move 8X the original distance so 0.8mm. However, due to the mass and inertia, the motor doesn’t stop it as easily as before so it goes 0.9mm. This would be “slam”.
Conversely, perhaps with an overdamped driver, the damping has more of an effect at higher excursions and instead of the distance being the 0.8mm (as in the above example), maybe it’s 0.7mm instead. You lost dynamics. This can be thought of like blowing air through a sponge - it’s not hard to blow a tiny bit of air through it (small signal), but it’s very hard to blow a lot of air through it - you encounter a lot of resistance (large signal aka dynamics).
Does it make sense or am I not explaining well?
I understand what you are saying, but you may be talking about semi-clipping or clipping instead of slam. To my ears the Elex sounds like it has a too-heavy driver and leans toward clipping and exaggerated dynamics in ordinary use. It can be induced to clip hard (making a metallic clack-clack-clack sound) rather than distort with bass tracks. Your explanation seems to fit it very well.
Regarding slam, some systems are able to rapidly produce louder sounds while others can’t change volume as quickly. Fast setups slam when they generate appropriate peak volume levels and remain far away from clipping. This can result from lively headphones (e.g., non-Elex/Elear Focal), an amp (e.g., high gain), or both.
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