Stax SR-009S Electrostatic Headphone Review

[Robbo99999]

My vote is "not terrible" considering one might buy this cheaper than the Stax:

Dan Clark Stealth Review (State of the Art Headphone)

This is a review and detailed measurements of the just announced Dan Clark Audio Stealth closed back planar magnetic headphone. Company was kind enough to share with me a couple of samples which I have been testing and playing with in the last couple of weeks. It costs US $3999. The price...

www.audiosciencereview.com

and spend the rest for a very decent HPA. And, last but not least, not having to bother with EQ as a "bonus".

I know, I definitely had my mind on The Stealth when thinking about price comparisons to this Stax, and that's not taking into account cheaper headphones that measure better than the Stax too.

(I'm pleased that Amir had the strength of mind/character to give it a glowing subjective review despite some of it's measured imperfections, as it's useful/interesting to take some of those subjective points into account, and a genuine subjective review is important.)

 

[ocinn]

I demoed these and had zero complaints about the bass. Yes, it is recessed but I was not getting any distortion or breakup at extremely high levels, and a shelf filter could have been placed without sacrificing sane output levels. The upper treble went first, IME.

It was powered by a Mjolnir Carbon (CC?, I don't recall), which I would hope has significantly more clean power than the entry-level SRM-313. That being said it was by far the best headphone experience I've ever heard in my entire life, actually brought me to tears.

And, I've heard DCA Expanse, etc... Owner had BAACH as well and we tried the "speaker projection" with head tracking, and while it wasn't calibrated for my ear/head shape, it was pretty mindblowing, and not something I will ever forget. Has completely ruined all other headphone listening for me now.

 

[Ambient384]

Please somebody educate me, so this headphone had good performance in distortion levels which I thought means friendly for EQ; but “shelving filter caused severe distortion at anything but moderate levels” so now I’m confused

Could be excursion limits kicking in hard since Electrostatics seem to have less space than Planar & BA drivers do. There are theories saying this Is why the Shure KSE1200 & KSE1500 are 1% at 1KHz/100db.

 

[VietnamRadioEnjoyer]

Please somebody educate me, so this headphone had good performance in distortion levels which I thought means friendly for EQ; but “shelving filter caused severe distortion at anything but moderate levels” so now I’m confused

Over Excursion in bass. Your ears hear the mid frequencies louder than bass at equal DBSPL so bass needs to be louder. but there is a limit much driver can move, but unlike non EST drivers, it stay distortion-less until it hits its limit. this is because EST drivers are lighter than the air they move so air can act as a dampening factor eliminating distortion

 

[NoteMakoti]

4 and a half stacks and the bass is still anemic, even with EQ? Nah, I'm Jamaican, I couldn't live with that.

 

[Madlop26]

Could be excursion limits kicking in hard since Electrostatics seem to have less space than Planar & BA drivers do. There are theories saying this Is why the Shure KSE1200 & KSE1500 are 1% at 1KHz/100db.

Over Excursion in bass. Your ears hear the mid frequencies louder than bass at equal DBSPL so bass needs to be louder. but there is a limit much driver can move, but unlike non EST drivers, it stay distortion-less until it hits its limit. this is because EST drivers are lighter than the air they move so air can act as a dampening factor eliminating distortion

Thanks!, but that would not be shown in the lower frequencies doing the THD test?

 

[oceansize]

Thanks!, but that would not be shown in the lower frequencies doing the THD test?

 

[amirm]

I should note that this headphones back radiation into the room was the loudest I have heard. So @solderdude may be right that some room interference may be in play here.

 

[oleg87]

How's the headband mechanism on these? I had a hell of a time getting a solid seal on some of cheaper Stax that didn't make the bass response super sensitive to me moving my head. Sounded great but usability left a lot to be desired.

 

[amirm]

Please somebody educate me, so this headphone had good performance in distortion levels which I thought means friendly for EQ; but “shelving filter caused severe distortion at anything but moderate levels” so now I’m confused

This is a unique headphone in that it goes from no distortion to severe distortion just a hair higher in volume. It doesn't gradually, or even non-linearly increase distortion. It just falls apart at a precise point. If I had post the 114 dBSPL numbers it would have been off the charts. For this reason, I wouldn't use one's normal intuition from other headphones to apply here.

 

[amirm]

How's the headband mechanism on these? I had a hell of a time getting a solid seal on some of cheaper Stax that didn't make the bass response super sensitive to me moving my head. Sounded great but usability left a lot to be desired.

It is a soft and wide leather piece that goes over your head to support it. Fortunately, it has up down adjustments on each side unlike older Stax headphones. Alas, even its lowest setting, it would barely seal on my head and not at all on the fixture. On the latter, I had to put something under the strap to close the two cups otherwise they would not seal.

 

[solderdude]

Thanks!, but that would not be shown in the lower frequencies doing the THD test?

IF Amir would have published the 114dB test you would have seen a boatload of distortion and is why Amir only showed 110dB.
Just above it there is hard limiting. With headphones like this it becomes very audible.
It is not the headphone that is at fault but the SRM313. With the SRM717 the 114dB could be reached.
The problem here, with shelving, is that the max. voltage limit is reached and that will give a 'harsh' clipping even when the subbass note just reaches that clipping point.
With the suggested EQ the low subbass is not amplified only the low bass is a little.

Note the max. SPL is 118dB (@400Hz) which is loud enough for impressive levels but requires 708rms (1kV peak)
550V on one stator and -550 on the other stator with 580V bias voltage on the membrane, so almost double the bias voltage. The SRM313 simply cannot reach that. When EQ'ing to Harman one simply hard-clips the amp which does not sound nice. A bit similar to the hardclipping some of the early Focal headphones.

With another energizer the discussion might have been different.

Edit: Seems I was crossposting with Amir.

 

[amirm]

To answer why the diversion between measurements and subjective results, there really needs to be more research into spatial qualities of headphones. The ones with larger cups and Stax here, clearly have a characteristic not captured in pure frequency response. Actually, frequency response may be a co-dependent factor as well as I see how having more 2 to 3 kHz energy enhances this effect. This latter we could simulate with EQ but the large driver effect can only be tested using actual headphones making the test essentially non blind.

 

[Roland301]

I guess Stax have the advantage of making custom amplifiers for these cans so it wouldn't perhaps be too difficult to build a suitable analogue equaliser with a few op-amps to do away with those frequency response anomalies without causing too much distortion? 81dB is certainly impressive!

They actually created this for several older models; there are the ED-1 Professional (lambda pro), ED-1 Signature (lambda signature), ED-5 (sr-5), and ED-1 Monitor (Pro eq and amp in one box).

They eq the respective models to diffuse field curve and I believe Gunther Thiele was consulted in their design and they are mentioned in one of his papers.

You can find digital EQ curves for them online, although they are of limited usefulness due to many Lambda units these days having the original rockwool back foam removed due to age.

 

[solderdude]

There is something else going on with stats when it concerns bass response and the perceived 'lack' of it.
Marvin (SBAF) has made some burst measurements which include a Stax.

Above you see the Stax having to 'swing in' for 100Hz (which is a high bass note) and given that the first wavefront is important to how something sounds and music only consists of transients one can see that EQ'ing won't do much for the first wave front and may sound the bass aenemic even when it looks fine on an FR plot.

Read more about this here:

Burst Response! HD800, SR-207, HD650

Inspired from @Serious's work here: http://www.superbestaudiofriends.org/index.php?threads/stax-sr-202-srm-212-measurements.3608/#post-107440 I'm glad...

www.superbestaudiofriends.org

Do note that I don't agree with everything that is written there but like the experimenting and attempts made.

 

[gnarly]

Nice to see a Stax review
I'm still holding on to Lambda Pro and Lambda Pro Signatures, with their solid state SRM-1/MK-2, and tube SRM-T1 amps, respectively.
I use them as a reference for DIY speakers, when it comes to hopefully attainable detail and air.

With these models too, totally agree on the need for some bass boost.
I use a Manley Massive Passive EQ with the Stax, and together they work very well in dialing in tracks to taste.

I've never measured any headphones SPL, and have no clue re my listening levels ......other than to say I probably have some of the loudest speakers seen on ASR, and like to crank.
Can't say I've ever noticed any real deterioration with my Stax models at higher SPL, even with bass boost..

Looking at the Massive Passive faceplate, I see I use what is probably +10dB shelving, medium bandwidth gain. But it's hard to know exactly what you're getting with this EQ without running a transfer function..

But like said, no clue what the SPL levels are....I just know the sound stays clean pretty dang loud .

 

[martin900]

SR-X9000 is the true fun Stax, it has more warmth and way more low and than the 009(S). I've had one with the T8000 energizer.
I sold mine as I couldn't justify the total cost any longer (12k new) considering I was using it maybe once a week, it also felt scary that something might break.

If someone is looking for a stat that is more 'bassy' and has overall a warm presentation - SR-007mk2 is the no brainer. Not the most detailed but the heaviest sounding of all.
The X9000 was a nice hybrid of both the 7 and 9 in terms of sound signature.
I have owned various Lambda's, 404, 407, 202, 307 but the X9000 cannot be compared, different league. I was stunned when I heard the X9000 for the first time, if you think the Lambda sounded detailed, you haven't heard nothing yet. Give them a listen if you have an audio store nearby that stocks Stax and if you ever decide to buy one - get them with a different amp, the T8000 is not so good and uses unique parts, will be a dog to get repaired if anything goes wrong, Stax also refuses to provide any alignment procedures.

I also made the mistake of using them with a turntable (albeit a very high end one) and with a fancy cartridge (I used a Van Den Hul) you could easily hear the stylus itself moving in the LP groove. In the end it was just too much, way too detailed for vinyl playback.
No I'm not getting paid for writing this, they were just that bloody good

 

[JohnPM]

there are the ED-1 Professional (lambda pro), ED-1 Signature (lambda signature), ED-5 (sr-5), and ED-1 Monitor

They used to cheat a bit with the equalisers, dropping the overall gain 1 dB with the EQ in circuit. It made everything seem to move further out in the soundfield when switching from bypass to EQ active. Despite the trickery the equaliser made the lambda signature sound even more natural, almost uncannily so for vocals.

 

[martin900]

The problem with the old Lambda's is that they have a nasty bite somewhere in the midrange/HF range, it's difficult to describe but if you listen to, let's say high end AKG's or Sennheisers and then put the Lambda's back on, you will notice the high frequency sounds a bit 'etched'.
Still, I heard the Lambda Pro's on an SRM-1/MK2 Professional and it's shockingly good when you consider the year it was released.

 

[Ra1zel]

Nice review and it confirms what I already experienced with Stax headphones many times before, that they are very responsive to EQ, astonishingly clean and distortionless. Actually the #1 best over ear headphone expirience for me was the original SR-Ω from 1993 equalised to Harman AE/OE 2013, the close second is the same but on the new omega (SR-X9000), simply uncanny level of clean and imaging, SR-Ω also has the most powerfull bass of all electrostats essentially negating the only historical weak point.


Note for those confused about 110dB limit. There has to be some way to limit excursion, since if the audio signal voltage exceeds the bias voltage, the membrane will hit the stators, and then... boom, very costly boom. Edit: hard limit is higher but requires more powerful amp.