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The science behind Stax's magic

John_M

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BTW if you want to see low THD, the AirPods Max is a good contender : https://www.head-fi.org/threads/apple-airpods-max-measurements-brüel-kjær-5128.951184/

Apparently the Airpods are also very well tuned and the tuning of the SR-009 has been criticised. So in response to the original question - what, objectively, makes the Stax "better" - I don't know. I haven't heard the Airpods.

Just waiting for the ASR review/ comparison to Stax headphones. If there doesn't appear to be any objective reason why the Stax is 'better' and if I like the sound, I might sell up, get the Airpods and pocket the price difference. ;)
 

solderdude

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Jude now also measures distortion at 110dB SPL ?

Consider that the Airpods are ANC so bass distortion will be low as distortion is removed by ANC (when done properly)
 

MayaTlab

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So in response to the original question - what, objectively, makes the Stax "better"

Well the entire thread presupposes that they're better... I was just commenting on the idea that THD could be an explanation for that. IMO unlikely given that there are other decently measuring HPs as far as THD is concerned.
 

John_M

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So do you think there's some other advantage Stax headphones have (if so, what) or do you dispute that they're better?

As mentioned earlier, I have heard about "speed" but not sure whether/ to what extent this is a scientific rather than an audiophile concept.

Or is an element of it down to people being fed electrostat/ Stax expectation bias and reacting like this guy :)

 

MayaTlab

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So do you think there's some other advantage Stax headphones have (if so, what) or do you dispute that they're better?

I'm not an acoustician so I don't know. All I know is that quite frequently when another factor than frequency response is proposed as the cause for what someone hears, counter-examples aren't too hard to find (THD is an example).
And since frequency response at a specific listener's eardrum (and it might vary across listeners particularly at the two extremes) remains a very uncontrolled variable, it's probably there that the answer should be looked into first IMO - ie is there something with Stax' headphones that makes them more likely to deliver an FR curve at the listener's eardrum with some specific features that some people would consider desirable ?
For example, from what I understand the idea behind Rtings' PRTF measurement is that they made the hypothesis that some headphones interact with our pinna in a more "speaker-like" manner which could potentially enable them to produce an FR curve at a specific listener's eardrum that better matches what the listener's anatomy makes him / her expect to hear (provided the basal FR curve is correct). In another word that the variance at listeners' eardrums would match better with some headphones the variance we see at their eardrum when listening to speakers.
This is the sort of information for which measuring headphones on a HATS may not quite provide.
Measuring FR curve at listener's eardrums is a royal PITA and requires quite a bit of kit apparently (https://www.etymotic.com/auditory-research/microphones/er-7c.html) - and more importantly probably quite a good deal of know-how to start with. There's that paper for example, but there aren't that many to start with :
https://www.aes.org/e-lib/browse.cfm?elib=16877
I wouldn't be surprised to learn that companies working in surround sound simulations for headphones are increasingly gathering this sort of data en masse combined with 3D scans of the listeners' ears and their HRTF.
Now this is just me, but the more I'm learning how to effectively EQ headphones in a way that I hope increasingly corresponds well to my anatomy, the more I'm subscribing to the "let's look at FR at a specific listener's eardrum first and the rest second" crowd.

I've never listened to Stax' round headphones, but I've owned their SR507 for a few years. Didn't keep them. I never thought of them as magical, just different in an interesting way.

As mentioned earlier, I have heard about "speed" but not sure whether/ to what extent this is a scientific rather than an audiophile concept.

It doesn't have an operational definition, so we can't apply any form of scientific method to test for it for a start.
 
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Rthomas

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Interesting thread!

I spent about 4 weeks comparing my Utopia (with THX 789 Amp) to a friend's SR009 (with a Stax 353X amp). I was kind of hoping to prefer the Utopia as then I wouldn't need to buy an SR009S but ultimately the SR009S sounded ''better'' for the kind of music I listen to during my serious listening sessions.

Both headphones were EQed to the Harman target but even then each had a distinct flavour. I did not scientifically volume match but I'm confident I could pick out the headphones in a blind test even if they felt identical on the head.

The SR009 sounded a tiny bit more detailed in the treble. The soundstage or sound image was a bit larger (this made Classical music sound grander).

The 009 with EQ also seemed to be able to produce lower bass notes although the Utopia was slightly punchier and impactful. The Utopia had a fuller sound.

For me the tie breaker was my perception of how they reproduced female vocalists like Allison Krauss, Amber Rubarth etc. I felt like with the 009 the singer could have been in the same room as me whereas the Utopia sounded a tiny bit more like music reproduction.

All this could be my imagination but ultimately the Stax magic worked and I sold the Utopia and purchased an SR009S. If I was in the US I would gladly send it in for testing but I'm in the EU and don't want any chance of customs messing with my Precious :D

Utopia is a better allrounder but Stax is better for typical ''audiophile music'' IMHO.

Also I think anybody playing at these price levels needs to try to EQ the SR009 & SR007. I think with EQ they are good enough to cure the itch to upgrade for a long time. Without EQ I can think of a half dozen headphones who's tonal balance I prefer to the 009.
 
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Yoaime

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This gives them a very open and airy sound.
That would only but found in some very expensive Hifiman planar, presumably.
So, I guess if you want that transparent/open sound you take a SR-L300. If you want deep and impactful bass you get a planar (dan clark aeon ?). If you want both you rob a bank (007/HE1000 ?).
Stax headphones might truly have something special, or electrostatic in general.

EQ doesn't look to be able to get you there.

Does science still has it's limits to give us the exact why ?
Some random ideas :
- The very thin driver can react more quickly to change in the impulse or be more precise resulting in better fidelity. What measurement would confirm this, impulse response, step response, CSD plots ?
- Thin pads gives less room around your ears to create resonances altering the sound, L700 with thicker pads have been reported less transparent than 300.
- Ultra low distortion. RTings measurement doesn't agree though.

If Senn use stats for it's Orpheus they must have found that's this technology is in some ways better. But if that's the reason why aren't they making a model way less expensive with this like Stax can do. Profit margin ? Estats are too fragile ?
 

maverickronin

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If you want deep and impactful bass you get a planar (dan clark aeon ?).

I'm pretty sure the better bass impact you get from planar magnetics and dynamics is just because the diaphragm weighs more and thus gives you more moving mass coupled to your head.

I need to get some accelerators and actually prove this some day...

The very thin driver can react more quickly to change in the impulse or be more precise resulting in better fidelity. What measurement would confirm this, impulse response, step response, CSD plots ?

This is the intuitive conclusion but it's not correct. Physically, the "speed" of the driver is just how high it frequency response goes. The diaphragm has to move back and forth at any given frequency in order to reproduce it and move farther for higher SPL. As the driver's speed drops off, it's output at higher frequencies drops off.

Things get messier than that in real, physical systems, with linear ranges, breakup, and modes, but that's the basic concept. An infinitely fast driver would just have an infinitely extended frequency response.

Ultra low distortion. RTings measurement doesn't agree though.

This is true for the headphones. The problem is that they require so much gain that the amplifiers can let down the transducers at higher volumes. And bass distortion can go through the roof if you don't get a proper seal.

Compare Amir's measurements with Stax's amps to Tyll's who used one of the KG solid state variants.
 

Dealux

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In my experience most headphones tend to fall apart after 8 KHz. There's a severe lack in clarity compared to a really good set of speakers. Speakers have better linearity and will sound more detailed than the best headphones in most cases.

Sometimes some headphones can maintain control and clarity (i.e. lack resonances) in the upper regions of the treble and this creates the sense of "speed" that people talk about. I have actually experience this sort of phenomenon most reliably with in-ears. For some reason with those I get the least amount of resonances (dips or peaks) in the upper treble provided that I get the optimal insertion depth and the difference between linear treble response and the usual kind of response is night and day. You immediately feel like you are inside the recording when the resonances go away (but they never do so completely) and there's an extra level of separation for instruments. If I can get that out of cheap IEMs then it's pretty obvious that detail is nothing more than frequency response as experienced subjectively.
 

Ilkless

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The Shure website includes an explanation about electrostats generally, which includes a reference to transient response. They also talk about "fastest, most accurate transient response available" elsewhere on their site.

https://www.shure.com/en-US/headpho...why-audiophiles-love-electrostatic-technology


It's playing into enthusiast intuition. At the transducer level, speed is about extension as discussed earlier. And headphone parts agnostic of transducer design (eg. Earcup volume and design) can alter "speed" in terms of group delay, but those are not intrinsic to any transducer design.
 
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Yoaime

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So we don't yet have any measurement that can tell us about this property of headphones.
Untitled.png
 

2M2B

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Well the entire thread presupposes that they're better... I was just commenting on the idea that THD could be an explanation for that. IMO unlikely given that there are other decently measuring HPs as far as THD is concerned.

Also some high THD HPs can sound good like the Infamous ER4XR.
 

2M2B

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I had a brain fart there, Doing THD tests on IEM's actually harder than It looks so most charts are showing clipped mics. Since In this link he notices at 90 ~ 100db the rig's mic distorts at 90 ~ 100 db, while high end mics don't & show the ER4 being <0.2%. Cause I'm sure Etymotic touted the ER4S as being 92% close to electrostatic headphones, It really shows when i did a A/B with the ER4SR and the ER2XR(bass cut by -5 under 114Hz to mimic a 2SE).

https://www.head-fi.org/threads/ety...and-your-couplers.908512/page-6#post-15082479
 

Dealux

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Cause I'm sure Etymotic touted the ER4S as being 92% close to electrostatic headphones, It really shows when i did a A/B with the ER4SR and the ER2XR(bass cut by -5 under 114Hz to mimic a 2SE).
I think they mean that e-stats have similar response accuracy or better than their earphones. Not sure which e-stats. I think they're referring to the smoothness of the response in the treble which is definitely a nice feature on Etymotic IEMs but I cannot readily achieve the linear response with the stock tips myself. In fact it seems I can only achieve the "flat" response from 9K-16K (with a bit of an 11K peak) with the Shure olive tips and yes, they do sound like what people describe e-stats as. There's an extra sense of clarity and separation when the treble and upper treble are perceptually very smooth.

I am curious how the ER2XR stacks up in that regard. In measurements they appear to have more uneven upper treble but perhaps better extension.
 
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Yoaime

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I think they mean that e-stats have similar response accuracy or better than their earphones. Not sure which e-stats. I think they're referring to the smoothness of the response in the treble which is definitely a nice feature on Etymotic IEMs but I cannot readily achieve the linear response with the stock tips myself. In fact it seems I can only achieve the "flat" response from 9K-16K (with a bit of an 11K peak) with the Shure olive tips and yes, they do sound like what people describe e-stats as. There's an extra sense of clarity and separation when the treble and upper treble are perceptually very smooth.

I am curious how the ER2XR stacks up in that regard. In measurements they appear to have more uneven upper treble but perhaps better extension.
So in the end it would just be treble smoothness.
 

MayaTlab

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So in the end it would just be treble smoothness.

Possibly, but as I wrote FR curve at someone in particular's eardrum is increasingly divergent past a few kHz because of anatomical variations. So to some people some Stax headphones will sound as peaky as some other headphones. And some non-stats will sound "smoother" to some people than some Stax headphones.
The paper I already linked to measured a few Stax headphones on real humans with probe microphones near the eardrum. The measurements are likely to be not particularly accurate past 10khz anyway (don't bother to look at the graphs past that value) but we can already see past 5khz just as much variation between listeners as with other headphones. Real ear measurements are quite susceptible to position of the tube inside the ear canal, so take it with a pinch of salt. But I'm highly sceptical that Stax headphones behave any differently from other headphones in that regard.
1449446210135.png

The thing is, we're back again to presupposing that Stax headphones have something extra others don't have and struggling to try to find what it is.
IMO that's not a great presumption for a start.
 

John_M

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The thing is, we're back again to presupposing that Stax headphones have something extra others don't have and struggling to try to find what it is. IMO that's not a great presumption for a start.

So do you dispute that Stax headphones are "special"? :)

I think the OP might mean electrostats more generally. Sennheiser, Hifiman, Shure, Dan Clark Audio and others have all picked the technology for their top of the line headphones/ earphones.
 
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