Stax SR-009S Electrostatic Headphone Review

[batcake]

Sr009s' stock tonality fatigues my ears after around 30 minutes. I think its lack of lower mids and upper bass causes me to turn up the volume higher than I'd normally listen to try to "feel" the music. I can mitigate this problem if set a +4 db low shelf q 0.7 at 500 hz to give it more punch and make it similar sounding to my other cans in that region without bass boost (sounds similar to the stock Focal Utopia imo). That said I prefer listening to it with Oratory1990's harman presets. With a srm-717 it has enough headroom to make compressed music very loud even with the full -10.5 db pre-amp (for bass boost) but I do have to set the knob close to max (around 2-3 o clock) to get "adequate" volume for some high dynamic range tracks. In this case, I'll just reduce the 34 hz low shelf boost to 0 and keep the +5.5 db 105 hz low shelf so that I can change pre-amp to -5.5 db and obtain noticeable amounts of extra volume. It still sounds very good with only the partial bass boost imo. Anyway the sr-009s is hard to recommend because I really hate its stock tonality but with EQ it is a 10/10. Voted fine panther.

 

[markanini]

There is a widespread belief among STAX users in various forums that the amp makes a dramatic difference to how the headphones sound. The claim is that the amp makes a much bigger difference to how an electrostatic headphones sounds than it does for a dynamic or planar headphone.

I've done some subjective A/B comparisons and find that the amp does make a difference, but much less than many seem to believe.

It would be amazing service to the community if @amirm could do amp/headphone measurements to answer this once and for all. For example, measuring the STAX SR-009S with a few different amps at different price points. Without this information, there will always be a question if ASR electrostatic headphones measurements reflect the headphone's performance or are showing the limitations of the amp.

I like this idea. Only affirming objective metrics is like an omission of the real world experience. Someone like a Amir has the audio tech experience and the heart in the right place for such a report.

 

[billqs]

Glad to see this review, long time follower, first time poster. I've been a Stax fan for a long time and would like to improve my experience of them by trying some equalization. Can anyone recommend an EQ device that could be integrated with my Stax systems? A complete newb here, what do I use, and where does it go? I assume it has to go after the headphone amplifier? My best Stax system is the older SR-007's with the Stax tube amp, which is widely thought to be underpowered, but would like to try boosting the bass with parametric EQ. They are pretty good at the lowest bass, but lack punch at mid-bass. All in all, I usually just leave them in the box and use dynamic phones since those've gotten so good. Thanks for any tips.

Hi! You don't mention which Stax Tube Amp you have, but I do have to mention that the SR-007's are the hardest Stax Estats to drive. You might want either a) easier to drive STAX like the Lambda series (although even the SR-009 is easier to drive than the 007), or get a higher voltage swing amp. Since I went back to vintage Lambda's I can drive them just fine with an SRD 7 SB transformer box coming off of my McIntosh MHA 100.

As to cost, have you guys never heard of the used market? I paid $300 for my first pair of STAX and $79 for a transformer box. Now, it was (for me) a gateway drug, but you don't have to spend a ton to see just what (both positive and negative) estats bring to the table.

 

[AudioJester]

There is a widespread belief among STAX users in various forums that the amp makes a dramatic difference to how the headphones sound. The claim is that the amp makes a much bigger difference to how an electrostatic headphones sounds than it does for a dynamic or planar headphone.

I've done some subjective A/B comparisons and find that the amp does make a difference, but much less than many seem to believe.

It would be amazing service to the community if @amirm could do amp/headphone measurements to answer this once and for all. For example, measuring the STAX SR-009S with a few different amps at different price points. Without this information, there will always be a question if ASR electrostatic headphones measurements reflect the headphone's performance or are showing the limitations of the amp.

Do you mean different amps result in different frequency response curves?

 

[solderdude]

They actually do with a lot of Stat amps. It is not like stat amps have to provide a low voltage into a resistive load.
Instead they need to have a (balanced) high voltage swing with very high dV/dt (rise and fall times) into a capacitive load.
This makes them a lot harder to build.
Transformers, tubes and high voltage MOSFETs or transistor stages also make measurable differences.

This makes it very hard to measure such amps too (high voltage and no resistive but purely capacitive load)

 

[Henreid]

All of these superlatives aside, company should have focused more on getting a better out of box response out of the headphone. Sources of resonances should have been found and fixed. I know it will never happen but inclusion of filtering in the amplifier would go a long way toward eliminated the need for external EQ. If they don't want to do it in digital domain, they can do so in analog.

I can't recommend the Stax SR-009S without EQ. With EQ, it is a wonderful headphone and highly recommended for low to medium level listening.

$5000+ Stax electrostatics that can't be recommended for their out-of-box performance.
I sincerely have no objection to equalization. I also recognize that equalization involves tuning headphones to each individual's unique "Harman curve". But here is what hurts my brain: I've lost count of the number of reviews I've read that appraise the headphones in these terms - "Without equalization, these headphones are okay. With equalization, these headphones absolutely sing." So often, we read this statement after the reviewer has tuned the headphones to conform more closely to the standard Harman curve. It just strikes me that manufacturers would sell more of their models if those headphones were tuned to perform at their best, right from the start. Buyers can still tweak that tuning however they desire, to their heart's content.
I apologize if this seems like a bit of a rant. I'm just puzzled...

 

[solderdude]

It is not easy to 'tune' a headphone in a certain way with very simple 'tuning methods' at hand that do not require difficult (expensive) production methods.
Not all drivers in enclosures can reach a certain target and there are limits to what can be achieved with acoustic materials (paper, felt, silk, cloth) and pads.
Afterall, all manufacturers are there to make money and all importers and retailers as well.

 

[BrooklynNick]

$5000+ Stax electrostatics that can't be recommended for their out-of-box performance.

Lets keep in mind that while the measurements here are objective, the statement in the review that EQ is needed is purely subjective. Thousands of STAX SR-009/SR-009S users would disagree that EQ is required to get good sound. I do EQ mine though and they sound really good. But, even without EQ, I think they sound very good with some minor issues.

 

[Henreid]

As always, questions, comments, recommendations, etc. are welcome. Click here if you have some audio gear you want me to test.

I've been researching headphones to find the best model I can afford. I've encountered 2 problems that make me hesitate. 1) I listen to Classical music over high-quality loudspeakers, and by comparison, headphones don't seem lifelike. 2) It appears that equalization is almost universally recommended for headphones (I'm okay with that). However, I have thousands of CDs, and it's proving difficult to find the means to equalize headphones precisely when using a CD player as the digital source. The DSP hardware to accomplish that is rather scarce and rather expensive. Has a DSP/Equalizer been reviewed that would work in my situation? I'm beginning to wonder if I should invest in headphones at all. Does anyone have suggestions/encouragement to help me move beyond my analysis paralysis? Thanks.

 

[solderdude]

There are quite a few headphones that perform well without EQ or maybe only need some passive filtering which makes them suited for analog and CD playback without having to resort to digital EQ.
The thing is... they won't sound like speakers. They will sound like good headphones. Headphones are an alternative for speakers when you cannot play loud or want high quality sound outside of the living/listening room.

You would have to accepts that both speakers and headphones can be high quality but differ in the way they present things.

Also headphones don't HAVE to comply to some target that will suit most people.
As they are very personal, they only have to sound good to you AND be comfortable to you and only you.
Some headphones sound perfectly great out of the box even if they don't 'measure' well or follow some preference curve.

 

[Robbo99999]

I've been researching headphones to find the best model I can afford. I've encountered 2 problems that make me hesitate. 1) I listen to Classical music over high-quality loudspeakers, and by comparison, headphones don't seem lifelike. 2) It appears that equalization is almost universally recommended for headphones (I'm okay with that). However, I have thousands of CDs, and it's proving difficult to find the means to equalize headphones precisely when using a CD player as the digital source. The DSP hardware to accomplish that is rather scarce and rather expensive. Has a DSP/Equalizer been reviewed that would work in my situation? I'm beginning to wonder if I should invest in headphones at all. Does anyone have suggestions/encouragement to help me move beyond my analysis paralysis? Thanks.

I don't adopt quite the same position as solderdude's post above mine (although I agree with him that headphones will present the soundstage/imaging differently than speakers). I'm more of the mindset that your best bet is to start off with an Oratory EQ from here:

index/list_of_presets - oratory1990

r/oratory1990: Mostly covering topics like headphones, in-ear headphones, acoustics, electroacoustics, acoustic tuning, headphone design …

www.reddit.com

So you'd probably choose a headphone that measures well from that list above, and possibly one that has been measured by Amir here on ASR that measured & reviewed well.
Then you use his user customisation filters to tweak the sound to your liking (if required, because sometimes it can be fine just using his EQ with no changes). An example of the user customisation filters are in the following pic, which just happens to be an EQ for the Sennheiser HD560s (just as an example), the user customisation filters are circled in red, so you're use those to tweak to your taste, bass first, then the other areas:

To apply the EQ you'd probably use the miniDSP Flex that Amir has measured (given that you said you were restricted to using a CD player in your chain rather than something flexible like a PC or phone):

Minidsp Flex Review (Audio DSP)

This is a review and detailed measurement of the Minidsp Flex audio signal processor. It was sent to me by the company and costs US $475 for unbalanced and $550 for balanced that I tested. Flex borrows the interface from SHD and puts it in a compact package. Seeing how I really liked that...

www.audiosciencereview.com

There's probably a fair learning curve associated with miniDSP software (you set them up initially using a PC (assuming with miniDSP Flex the same applies) and then they can operate "standalone" in your chain), but once you've got the hang of it then it's fine.

Failing all that (if too complicated & additional cost) then buy a headphone that measures well that has been reviewed by Amir (and also measured by Oratory just so you can see measurements from more than one source), and then just use it at stock without any EQ.

Restricting yourself to using a CD player is reducing your options to apply Parametric EQ, so it's not ideal, so you might be best to also rethink that restriction. It's cheaper & more flexible to be using a PC or phone or something where you can apply Parametric EQ right at the source.

 

[Henreid]

To apply the EQ you'd probably use the miniDSP Flex that Amir has measured (given that you said you were restricted to using a CD player in your chain rather than something flexible like a PC or phone)
Restricting yourself to using a CD player is reducing your options to apply Parametric EQ, so it's not ideal, so you might be best to also rethink that restriction. It's cheaper & more flexible to be using a PC or phone or something where you can apply Parametric EQ right at the source.

Thanks for your thoughtful, clear, and detailed answer to my question. I'm glad that there is an approach I can take to solve this problem. (Now I just need to decide which headphones to buy. I'm finding the reviews on Audio Science Review to be very helpful...)

 

[Jimbob54]

I've been researching headphones to find the best model I can afford. I've encountered 2 problems that make me hesitate. 1) I listen to Classical music over high-quality loudspeakers, and by comparison, headphones don't seem lifelike. 2) It appears that equalization is almost universally recommended for headphones (I'm okay with that). However, I have thousands of CDs, and it's proving difficult to find the means to equalize headphones precisely when using a CD player as the digital source. The DSP hardware to accomplish that is rather scarce and rather expensive. Has a DSP/Equalizer been reviewed that would work in my situation? I'm beginning to wonder if I should invest in headphones at all. Does anyone have suggestions/encouragement to help me move beyond my analysis paralysis? Thanks.

The simple but not cheap answer to your problem is an rme adi 2 dac FS . Will drive almost any headphone , has 5 band plus 2 shelf filters peq, crossfeed etc and will take either a coax digital or optical input from your cd player .

But like I say , not cheap

 

[Robbo99999]

The simple but not cheap answer to your problem is an rme adi 2 dac FS . Will drive almost any headphone , has 5 band plus 2 shelf filters peq, crossfeed etc and will take either a coax digital or optical input from your cd player .

But like I say , not cheap

And also less parametric EQ options than the miniDSP Flex. Granted you have to buy a headphone amp to connect to the miniDSP Flex, but that's still less money than RME ADI 2. And miniDSP Flex also has optical input (TOSLINK) from the CD Player.

 

[Jimbob54]

And also less parametric EQ options than the miniDSP Flex. Granted you have to buy a headphone amp to connect to the miniDSP Flex, but that's still less money than RME ADI 2. And miniDSP Flex also has optical input (TOSLINK) from the CD Player.

True. But there's a strong argument that if you buy a headphone that needs more than 5+2 eq bands, it's not the right HP.

Cant argue regarding the costs though.

 

[Robbo99999]

True. But there's a string argument that if you buy a headphone that needs more than 5+2 eq bands, it's not the right HP.

Cant argue regarding the costs though.

I don't really subscribe to that string argument though, and Oratory EQ's use 10 bands so it's convenient anyway - and using the extra bands doesn't make it sound worse, just gives you more options & flexibility.

 

[Jimbob54]

I don't really subscribe to that string argument though, and Oratory EQ's use 10 bands so it's convenient anyway - and using the extra bands doesn't make it sound worse, just gives you more options & flexibility.

It's possible I meant strong argument

 

[solderdude]

Now I just need to decide which headphones to buy

Budget ?
Open or closed ?
Over-ear, on-ear, in-ear ?
Portable or only in the home ?

 

[Robbo99999]

It's possible I meant strong argument

lol, I thought you were just being creative with your wording - "string argument" - I imagined the next loosely aligned/related argument linked/threaded onto the metaphorical string of conversation!

 

[Henreid]

The simple but not cheap answer to your problem is an rme adi 2 dac FS . Will drive almost any headphone , has 5 band plus 2 shelf filters peq, crossfeed etc and will take either a coax digital or optical input from your cd player .

But like I say , not cheap

Many thanks - those components look superb. You're right about the price! It's a serious investment.