Stax SR-009S Electrostatic Headphone Review

[Jeromeof]

@amirm Very interesting review and especially listening impressions. I wonder technically what is making the difference that you hear? Are there specific tracks that really stood out during your listening? Is it the openness of the earcup design or is it the treble response of the electrostatic drivers?

As my only experience with Electrostatic is the new Fiio FX15 "tribrid" IEM :

FiiO FX15 - Measurements, Features and Opinions

FiiO kindly sent me pre-release versions of 2 of their new IEM’s, the FH11 https://www.fiio.com/fh11 (1 DD + 1BA drivers) and the FX15 https://www.fiio.com/fx15 (1 DD + 1BA + 4EST drivers). Of these the FH11 is a very bass heavy IEM at roughly $50 with, in my opinion, an odd tuning (I asked FiiO...

www.audiosciencereview.com

which I found had fantastic treble which made certain tracks really stand out and appear very spacious for an IEM but ultimately I had to eq the midrange to get a balanced sound.

 

[vkvedam]

Nice, I listened to the original 009 few years ago, it was a very good experience. It's not something I could accommodate in the normal family life, may be after retirement

 

[LTig]

This review reminds me of my HD800 which also has flat bass and (but not my aging ears) screaming treble but still has qualities in its spatial representation of soundstage which are unsurpassed by any other headphone - well maybe now by this one ...

 

[solderdude]

Here are some thoughts about the EQ.

Notes about the EQ design:

• The average L/R is used to calculate the score.
• The resolution is 12 points per octave interpolated from the raw data (provided by @amirm)
• A Genetic Algorithm is used to optimize the EQ.
• The EQ Score is designed to MAXIMIZE the Score WHILE fitting the Harman target curve (and other constrains) with a fixed complexity.
  This will avoid weird results if one only optimizes for the Score.
  It will probably flatten the Error regression doing so, the tonal balance should be therefore more neutral.
• The EQs are starting point and may require tuning (certainly at LF and maybe at HF).
• The range around and above 10kHz is usually not EQed unless smooth enough to do so.
• I am using PEQ (PK) as from my experience the definition is more consistent across different DSP/platform implementations than shelves.
• With some HP/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
• Not all units of the same product are made equal. The EQ is based on the measurements of a single unit. YMMV with regards to the very unit you are trying this EQ on.
• I sometimes use variations of the Harman curve for some reasons. See rational here: https://www.audiosciencereview.com/...pro-review-headphone.28244/page-5#post-989169
• https://www.audiosciencereview.com/...pro-review-headphone.28244/page-6#post-992119
• NOTE: the score then calculated is not comparable to the scores derived from the default Harman target curve if not otherwise noted.

Good L/R match.

I have generated one EQ, the APO config file is attached.

Score no EQ: 68.0
Score Amirm: 71.0
Score with EQ: 77.0

Stax SR-009S APO Score Full EQ Flat@HF 96000Hz
August242023-160624

Preamp: -8.5 dB

Filter 1: ON PK Fc 26.47 Hz Gain 8.50 dB Q 0.36
Filter 2: ON PK Fc 1092.31 Hz Gain -4.88 dB Q 2.24
Filter 3: ON PK Fc 2594.12 Hz Gain 3.58 dB Q 0.90
Filter 4: ON PK Fc 4958.45 Hz Gain -7.37 dB Q 6.00
Filter 5: ON PK Fc 6039.98 Hz Gain 5.98 dB Q 2.76
Filter 6: ON PK Fc 1769.48 Hz Gain -2.52 dB Q 5.01

View attachment 307599

While technically, to get Harman type bass, your proposed EQ in the bass seems logical I would not recommend it.
The Stax headphone will not sound quite good with this kind of EQ in the bass.
Amir's EQ is about the max. it should be given.
This EQ will eat up 9dB of headroom giving about 100dB SPL peaks for bass notes. In such case you could only use it at moderate volumes.
Electrostat's Achilles heel is large excursions in the bass due to the high mechanical tension of the membrane to prevent 'sticking'.

 

[FrantzM]

Hi

Interesting.
Does the violent $4545 price include the headphones amplifier/driver?

An interesting headphones, I would say. Spatial qualities is an interesting take and I believe those I get from my headphones are up there too... I need to audition the HD800S to see how far its spatial quality are from those of my HifiMan H6SEv2..
I don't feel the need for an upgrade in headphones... I am an audiophile .. 'nuf said

Peace.

 

[Veri]

While technically, to get Harman type bass, your proposed EQ in the bass seems logical I would not recommend it.
The Stax headphone will not sound quite good with this kind of EQ in the bass.
Amir's EQ is about the max. it should be given.
This EQ will eat up 9dB of headroom giving about 100dB SPL peaks for bass notes. In such case you could only use it at moderate volumes.
Electrostat's Achilles heel is large excursions in the bass due to the high mechanical tension of the membrane to prevent 'sticking'.

Interesting, thanks for chiming in solderdude

 

[abdo123]

While technically, to get Harman type bass, your proposed EQ in the bass seems logical I would not recommend it.
The Stax headphone will not sound quite good with this kind of EQ in the bass.
Amir's EQ is about the max. it should be given.
This EQ will eat up 9dB of headroom giving about 100dB SPL peaks for bass notes. In such case you could only use it at moderate volumes.
Electrostat's Achilles heel is large excursions in the bass due to the high mechanical tension of the membrane to prevent 'sticking'.

Is this some sort of IMD? cause Amir's HD graphs show that even 100dB + EQ should be absolutely fine. Heck the distortion at 94 dB is noise!

 

[milosz]

I think the SR-007 (original version) is a better sounding headphone than the 009, if used with an amplifier that can swing a good amount of undistorted voltage like a Carbon, KGHVSS, etc. I think the 009 is perhaps too "polite." (And now there is the new Stax TOTL the SR-X9000 which I have yet to see; https://staxheadphones.com/collections/earspeakers/products/sr-x9000 )

Just like the SR-009 , the SR-007 also needs some EQ to bring out it's best, there's a number of good suggested curves available online.

I like my SR-007 / Carbon combo almost as much as I like my Dan Clark Stealth / Monolith amp setup. The Stealths don't need any EQ really, though I sometimes add some bass because I can't seem to get them to seal 100% properly on my ears. The Stax and the Stealth 'phones are different experiences, but both very enjoyable.

Since I bought the Carbon amp for the SR-007's that I had for a few years, and bought the Stealths, I haven't been tempted to buy any headphones or amps. Kind of feels like "end game" for me, after years of buying and then selling on various 'phones and amps.

 

[Bow_Wazoo]

I had the 009s from 2 years ago, to compare with the Utopia here. After Harman target, the 009s were fantastic. I think the build quality is worth mentioning. This is absolutely unacceptable. Judging by the price, the word is "unacceptable", a gross understatement!
Every 200 € Hifman feels much more valuable.

 

[MyCuriosity]

I've tried these headphones and are nothing short of fantastic. The only limitation is the bass extension.

 

[Yasuo]

Nah, I'm on the same old mindset - a headphone at this price point must sound at least good without any EQ.

 

[Veri]

I had the 009s from 2 years ago, to compare with the Utopia here. After Harman target, the 009s were fantastic. I think the build quality is worth mentioning. This is absolutely unacceptable. Judging by the price, the word is "unacceptable", a gross understatement!

I'm on the same mindset - a headphone at this price point must at least be of good build quality. At least.

 

[Cuckoo Studio]

If anyone curious about SR-009（without S）here are some data I measured.

SR-009：

104dBSPL in % mode：

 

[solderdude]

Is this some sort of IMD? cause Amir's HD graphs show that even 100dB + EQ should be absolutely fine. Heck the distortion at 94 dB is noise!

It just 'eats' 10dB of the max 110dB SPL. So a headroom thingy. Of course this will only happen when substantial amounts of low bass is present. With The SRM717 it will be a bit higher.

 

[abdo123]

It just 'eats' 10dB of the max 110dB SPL. So a headroom thingy. Of course this will only happen when substantial amounts of low bass is present. With The SRM717 it will be a bit higher.

how come Amir is experiencing distortion?100dB is insane!

 

[Chester]

Nah, I'm on the same old mindset - a headphone at this price point must sound at least good without any EQ.

Subjective of course but I think it does sound good without EQ, it appears it can be improved further though.

 

[Jimbob54]

how come Amir is experiencing distortion?100dB is insane!

I guess the amp giving up?

Edit- No, see Solderdude posts, seems it driver excursion due to more LF than the driver can handle. No distortion to high distortion

 

[solderdude]

how come Amir is experiencing distortion?100dB is insane!

100dB peak SPL in the low bass in music is far from insane levels.
It is about 75phon (we hear in phon's not dB). This could be the case when such heroic EQ is applied and one wants to play at comfortably loud levels.
The major drawback of electrostatic headphones is maximum SPL.

This is why testing headphones at 114dB is not as crazy as some think.
Peak SPL is something very different from average dBA noise levels.

 

[Ken Tajalli]

• The EQs are starting point and may require tuning (certainly at LF and maybe at HF).
• With some HP/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
• Not all units of the same product are made equal. The EQ is based on the measurements of a single unit. YMMV with regards to the very unit you are trying this EQ on.

+1

 

[the_brunx]

The amp is most likely causing the distortion after 110dB, this is one of the biggest problem with electrostatic headphones, the amps don’t put out enough voltage for the headphones to go louder without distortion. Not even the big ones, Except if you are using a transformer setup.