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Stax SR-009S Electrostatic Headphone Review

Rate this headphone:

  • 1. Poor (headless panther)

    Votes: 47 20.1%
  • 2. Not terrible (postman panther)

    Votes: 63 26.9%
  • 3. Fine (happy panther)

    Votes: 78 33.3%
  • 4. Great (golfing panther)

    Votes: 46 19.7%

  • Total voters
    234

Zoide

Active Member
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Oct 20, 2018
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Going back to my everyday Stealth the sound was tonally more balance with better bass. But it was much more closed in. I didn't get a chance to compare to Expanse.
@amirm What can explain the more "closed in" sound of the Stealth vs the 009S, given that there's nothing "magic" about electrostatic headphones and that the Stealth measures much better in terms of Harman FR compliance and group delay?

I currently have the STAX SR-007MK2.9 (spring and blu-tack) modded and have been very tempted by the glowing reports about the DCA E3. I fear losing the "magic" of my STAX, but I'm aware that that's a very subjective concern. That said, comments such as yours give me pause.

Thanks
 

2tec

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We all know that there are qualities to a headphone or IEM's that surpass good tonal compliance to a target and low distortion. You hear things about the difference between dynamic, planar, open or closed back, electrostatic etc. but I never see it backed up with data. Is it in group delay? Step response? Harmonics? I refuse to believe that it is a magic sauce that can't be measured.

I think many people are looking for these qualities but we are left to trust subjective reviews to find them. Which I think is quite frustrating.
I think it's inherent in the design. I own Quad 57s so I've heard the difference first hand. It's the fact that such a large area can move air yet that movement is being accomplished by a material that has almost no mass so it can respond to changes in the electrical (signal) field faster and in a more 'natural' way. That's my theory. And yes, the Quad 57s have the best mid range I've ever heard, subjectively speaking.
 

Svperstar

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I currently have the STAX SR-007MK2.9 (spring and blu-tack) modded and have been very tempted by the glowing reports about the DCA E3. I fear losing the "magic" of my STAX, but I'm aware that that's a very subjective concern. That said, comments such as yours give me pause.

I also have the 007 2.9, I almost got a used DCA Corina but the owner described it as darker then the CRBN, I love Audeze and the earcups are bigger so I went with the CRBN based off that.
 

jazzvinyl2020

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Jan 18, 2020
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For those who are interested in how much difference an electrostatic amp makes subjectively, I own the SR-009s (previously had 007 MK1) and drive them with a KGSSHV (DIY), I also experimented with a STAX SRM D50 and an SRM 252s. The 009s to my ears sounds absolutely identical when driven from either a D50 or the KGSSHV. It sounds horrible and compressed from a 252s. I assume it's simply lack of power and no other magical ingredient. My previous 007 MK1 sounded identical on the D50 compared to a KGSSHV unless you were pushing it really hard. Again, I suspect it's only a matter of power and nothing else. Anyone who tells you you "need" an expensive amp is imagining things. I've tried most of the overhyped products including Blue Hawaii and other exotic amps on my 009s. All of them sounded not better or worse than a regular decent STAX energizer. I know, head-fi readers are going to crucify me for this :)
 

lewdish

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May 29, 2021
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Anyone w/ a SR009s comment on how it sounds compared to hd800s soundstage and imaging?
 

jazzvinyl2020

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Jan 18, 2020
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Anyone w/ a SR009s comment on how it sounds compared to hd800s soundstage and imaging?
My friend owns a HD800 and we did a head-to-head comparison. The HD800 projects images further away as if you're listening from a distance. Images seem to be far left and right from your ears whereas the SR-009s projects a more realistic soundstage albeit with smaller dimensions.
 

Blockader

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Nov 17, 2021
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Location
Denmark
1711022333741.png


I believe the distortion observed above 104 dB SPL is not due to the headphones but rather the amplifier. Typically, as sound transducers approach their maximum SPL, they begin to distort significantly. However, this is not the case here. The driver maintains a very linear behavior, which suggests it has a much higher maximum SPL than 104 dB.

I recall that Oratory conducted tests on Stax drivers, which were capable of handling up to 130 dB without any issues. Interestingly, the THD+Nof the headphones he tested actually decreased at higher volumes. This means that the noise floor lowers with pushing more voltage to the headphones, while the distortion level remains constant.
 

staticV3

Master Contributor
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I recall that Oratory conducted tests on Stax drivers, which were capable of handling up to 130 dB without any issues. Interestingly, the THD+Nof the headphones he tested actually decreased at higher volumes. This means that the noise floor lowers with pushing more voltage to the headphones, while the distortion level remains constant.
The noise floor stays constant.
But the signal gets louder, and so SNR improves, and with it THD+N.
 

Blockader

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The noise floor stays constant.
But the signal gets louder, and so SNR improves, and with it THD+N.
Aren't we saying the same thing?

As the voltage increases, the fundamental signal level rises, which lowers the relative noise floor compared to the fundamental. The increase in distortion is smaller than the reduction in the noise floor, resulting in a lower THD+N.
 

Blockader

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@amirm What can explain the more "closed in" sound of the Stealth vs the 009S, given that there's nothing "magic" about electrostatic headphones and that the Stealth measures much better in terms of Harman FR compliance and group delay?

I currently have the STAX SR-007MK2.9 (spring and blu-tack) modded and have been very tempted by the glowing reports about the DCA E3. I fear losing the "magic" of my STAX, but I'm aware that that's a very subjective concern. That said, comments such as yours give me pause.

Thanks
Group delay deviations from a straight line indicate significant phase shifts. Humans determine the location of sounds by detecting phase differences between the ears, especially at high frequencies. Larger and consistent phase shifts can enhance sound separation and make the sound appear broader than the actual recording, among other effects.

In summary, for a more expansive soundstage, significant group delay spikes are beneficial. Moreover, if the amplitude of these spikes is uniform, it further enhances the imaging and separation. If you are measuring your speakers you can test this: Speakers have usually very large soundstage in rooms with little to no absorption, and group dleay measurements of speakers in an empty room looks messy and spikes are incredibly large.

1711023652290.png

I guess the first dip in the group delay graph happens due to GRAS test fixture, GRAS measurement fixtures cause a large 9khz dip due to the acoustic impedance mumbo jumbo happening there. Ideally headphones with large soundstage should have all 1 and 2 filled with spikes which are equal to the spikes around 2khz.
Some say the group delay measurements Amir takes is garbage. I do not know. That's probably another topic for another time.
 
Last edited:

Svperstar

Senior Member
Joined
Jul 4, 2018
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For those who are interested in how much difference an electrostatic amp makes subjectively, I own the SR-009s (previously had 007 MK1) and drive them with a KGSSHV (DIY), I also experimented with a STAX SRM D50 and an SRM 252s. The 009s to my ears sounds absolutely identical when driven from either a D50 or the KGSSHV. It sounds horrible and compressed from a 252s. I assume it's simply lack of power and no other magical ingredient. My previous 007 MK1 sounded identical on the D50 compared to a KGSSHV unless you were pushing it really hard. Again, I suspect it's only a matter of power and nothing else. Anyone who tells you you "need" an expensive amp is imagining things. I've tried most of the overhyped products including Blue Hawaii and other exotic amps on my 009s. All of them sounded not better or worse than a regular decent STAX energizer. I know, head-fi readers are going to crucify me for this :)

My year end bonus was bigger then I thought it was going to be so I have been thinking of going full crazy and getting a Carbon CC. They are $6900 + shipping. I worry I won't hear any difference between it and my Stax 717.
 

Svperstar

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When did that stop you ? :D

I hear a difference between the 717 and the T1S, it actually might just be in my head but there is something about the Topping EHA5 and the CRBN, it adds like a "sizzle" too the sound signature its hard to describe what I mean.

It would be cool if someone would hook up an estat to a measurement device and switch nothing but the energizer and record the output.
 

zachary80

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Aug 12, 2018
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I hear a difference between the 717 and the T1S, it actually might just be in my head but there is something about the Topping EHA5 and the CRBN, it adds like a "sizzle" too the sound signature its hard to describe what I mean.

It would be cool if someone would hook up an estat to a measurement device and switch nothing but the energizer and record the output.
Is this a pro or con for the EHA5? Thinking about picking it up on sale or waiting for STAX SRM-D10 II
 

Svperstar

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Is this a pro or con for the EHA5? Thinking about picking it up on sale or waiting for STAX SRM-D10 II

Pro. It's not a bad little amp just be wary of it's limits. When at high volume with EQ on compressed sounds, like badly encoded YouTube videos will make it shut off for a second. Note I was unable to get it to shut off listening to music.

I wish Schiit would come out with an estat amp.
 

strom

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May 31, 2020
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Pro. It's not a bad little amp just be wary of it's limits. When at high volume with EQ on compressed sounds, like badly encoded YouTube videos will make it shut off for a second. Note I was unable to get it to shut off listening to music.

I wish Schiit would come out with an estat amp.
I think I'll keep my Stax SRM323S until the dust settles...
 

solderdude

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It would be cool if someone would hook up an estat to a measurement device and switch nothing but the energizer and record the output.

Like this?

 

Svperstar

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Like this?


With different energizers, like a Carbon, KGSSHV, 717, T1S....
 

solderdude

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Amir only compared 2 different energizers but using the method you wanted ..
 
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