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A Review On: Stax SR-009 Electrostatic Headphones

Stax SR-009 Electrostatic Headphones

Rated # 56 in Over-Ear
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Pros: High level of clarity, relatively close to neutral, wide & open soundstage

Cons: Not as natural-sounding as OII MKI, flatter imaging than OII MKI

Originally published on November 11, 2012


Note: this review is an exact cross-post from post #1 of this thread on Head-Fi, which contains some user discussion on the review that may be relevant to read: http://www.head-fi.org/t/635893/mini-review-stax-sr-009

- download a printable 6-page PDF version of this mini-review (target goes to a location on my Dropbox)


I've been an owner of the HeadAmp BHSE for just over 3 years so far, which I use with the Stax SR-007 (OII MKI). My opinion of the OII/BHSE is that it forms the best headphone system that I've heard and is so amazing that it's changed me on the inside forever and continues to do so every time I listen to it.

Things just never stay still in the headphone world though, and when the SR-009 came out, of course I had to hear it. I got that opportunity at a few audio shows & Head-Fi meets over the last year, but those experiences didn't compel me enough to buy an SR-009 for myself. Despite that, I still remained optimistic and held out hope to one day hear one on my own system, to see if my CD player would make a difference. I finally got that chance recently thanks largely to CanJam@RMAF 2012, where I managed to acquire a loan from one of the most reliable sources that I know of (who shall remain nameless).

This mini-review is based on approximately 3 weeks of listening—not an ideal length of time for me, as I usually prefer to devote at least a month for a review, if not longer. My usual disclaimer applies: my opinion of the SR-009 shouldn't be considered final and is subject to change.

Reviewer Biases & Info, Equipment Setup, etc

For those who haven't seen it before, here's a link to one of my more recent mini-reviews; nothing has changed since then with the exception of my equipment setup: http://www.head-fi.org/products/audeze-lcd3-planar-magnetic-headphone/reviews/10298

Here's a breakdown of my current equipment setup:
- Source component: Plinius CD-101 (CD player) (power cord: Signal Cable Silver Resolution Reference - directly into wall)
- Analog interconnects: Emotiva X-Series XLR
- Headphone amplifier: HeadAmp Blue Hawaii SE w/ stock Mullard EL34 tubes (power cord: Parasound AWG12)
- Comparison headphones: Stax SR-007 (OII MKI)

Evaluation Music

CDs by the following artists/bands, by genre:

- Bluegrass: Alison Krauss & Union Station, Sierra Hull
- Classical: Carlos Kleiber & VPO, Julia Fischer, Nicola Benedetti
- Electronica/Trip-Hop: Goldfrapp, Massive Attack, Orbital, The Crystal Method, Trifonic
- Jazz: Dave Brubeck, Lee Morgan, Tord Gustavsen
- Rock: Porcupine Tree, Radiohead
- Metal: In Flames, Helloween, Megadeth, Meshuggah

Preconceptions & Initial Impressions

I had one big preconception of the SR-009 going into this review—I thought it would be like an electrostatic equivalent of the Sony Qualia 010. Not for any particular, logical reason, just an assumption based on informal listening in show/meet environments.

After having formally heard the SR-009 now, I'd now call my assumption to be false and I no longer think the SR-009 and Qualia 010 to be each other's equivalents in an electrostatic/dynamic kind of way. More to the point, I think the two headphones are clearly different from each other sonically. The Qualia 010 is probably best described as a very treble-oriented headphone, with a very wide & open soundstage, extremely clear-sounding, and fast (as in impulse response). To me, it remains the single clearest-sounding headphone that I've ever heard, of any type, eclipsing the SR-009 as well. Its treble also remains the best that I've heard to date—perfectly pristine and sharp. Not that the SR-009 had "bad" treble—it's just that I think the Qualia has the right amount of treble energy to make music sound realistically trebly, when necessary. I'm sure there are lots of people who would find the Qualia over-bright—but IMO, its treble quantity is perfectly realistic and remains my benchmark for all future headphones.

As far as initial impressions, to say that the SR-009 was a disappointment would be an understatement. I thought there'd be a significant difference between it and the OII MKI, but on first listen, I found that the two headphones were more similar than different and that the SR-009 didn't offer any immediately-obvious advantages over the OII MKI. It was clear that I'd have to do very critical listening in order to identify any sonic advantages it had.

Listening Test #1 - Synopsis

Although the OII MKI is admittedly my classical & jazz headphone primarily, I use it relatively often for other music genres as well, including electronica/trip-hop, folk/bluegrass, pop/rock, & metal. I consider the OII MKI as the single most "neutral"-sounding headphone that I've ever heard, of any type—almost every other headphone I've heard has had some type of overt sonic coloration, from brands like AKG, Audio-Technica, Beyerdynamic, Grado, Sennheiser, etc. The only other specific headphone models I'd class as close to "neutral" are the Grado HP1000 and JH Audio JH13 (IEMs). And no, I don't consider the Audeze headphones to be neutral either, though the LCD-2 r2 is certainly closer than the LCD-3. How do I define "neutral"? Mostly by the OII MKI and previously the HP1000—a balance between the bass, mid-range, & treble where none of them over-balance each other, providing a tone & timbre that sounds "realistic" when playing instruments that exist in real life, like a violin, which I'm intimately familiar with as a violinist. The OII MKI and the HP1000 are the only headphones, electrostatic or dynamic, that I've heard which I'd call neutral—none of the other full-size headphones I've heard to date deserve such a label, IMO.

With that said, I found that the SR-009 was relatively neutral-sounding too, though not quite as much as the OII MKI, with a marginal bass & mid-range detraction and slightly elevated treble. I'd summarize it as a somewhat brighter- and thinner-sounding OII MKI overall, but not excessively so, just marginally. And although I'd call the SR-009 "brighter" than the OII MKI comparatively, I wouldn't call the SR-009 "bright" per se, certainly not on the level of headphones like the Sennheiser HD800, let alone the Sony Qualia 010. The SR-009 was actually very well-balanced to me, easily more balanced-sounding than the dynamic (or orthodynamic) flagships that I've heard from Audeze, Beyerdynamic, and Sennheiser.

To summarize the SR-009's distinction versus the popular dynamics that I've heard: compared to both the Audeze LCD-2 and LCD-3, I'd say that it has a lot more clarity & treble quantity and a wider, more open soundstage. It's also more laid-back and passive-sounding compared to the assertive sound that the Audeze headphones have, without the visceral & tactile mid-range/bass either. I'd consider the SR-009 more loosely similar to the Sennheiser HD800, in that it has a similar level of clarity throughout the spectrum (but being better than the HD800), along with a similar passive sound, and a very generally similar sort of frequency-spectrum balance, except being better. Or to put it another way, I might say the SR-009 is sort of like a fixed version of the HD800 for me—less treble snarl/gnash, more mid-range quantity, more extended bass & treble, and a more accurate, smaller soundstage. (I'll note here that my HD800 thoughts are from it amped by the HeadAmp GS-X, and not a tube amp, which I might say is optimal for it.)

Listening Test #2 - Classical Music

My most critical listen throughout this review was classical music—specifically, the Adagio from the Violin Concerto in E major (BWV 1042) on Julia Fischer's Bach Concertos (or track 8 on this CD), which IMO remains the single best, most amazing display of prowess of the OII MKI/BHSE. There are so many awesome qualities that are revealed by the OII MKI, so my first question was, would this track sound even better on the SR-009?

No, it didn't, and the SR-009 actually ended up being somewhat of a bitter disappointment. Ok sure, the music still sounded technically "amazing" on the SR-009. It was also still way, way better than all of the dynamic headphones I've heard. And to its credit, it was still on the same plane of existence as the OII MKI.

However, the problem with the SR-009 was that it just wasn't as good as the OII MKI, and it had none of the OII's "magic" or x-factor either. On this track, the OII reveals so many details: Fischer's beautiful, pure, & radiating tone; a direct intimacy to her violin, so close you can practically hear into it; the vanishingly subtle rises & falls in intensity; an almost heat-like warmth quality; the organic sense of the orchestra. All of those details were subtracted with the SR-009—most of them completely! The SR-009's portrayal took away so many of those details that the music reverted to simply sounding like a really good pre-recorded performance and not something that was being played live, like the OII MKI can do.

I tried other classical CDs as well to round out the test and would put my position of the SR-009 for classical music this way: saying that the SR-009 is ideal for classical music would be like saying the same for the Sennheiser HD800—which is not something that I can personally agree with. I think of the HD800 to be a less-than-stellar headphone for classical due to some serious flaws, most notably the unrealistic & unnatural tone and timbre of the instruments in the orchestra, especially violins. It was the same way with the SR-009, which gave too much treble emphasis on violins so that they became wispy-sounding. Also like the HD800, the SR-009 "split" the 1st Violin section too much so that the violins sounded more like individual violins rather than a unified section body. There are only 2 headphones I've heard that properly portray the unified body concept, the OII MKI and the Grado HP1000—which should be the goal for accuracy, but most headphones fail to achieve it and the SR-009 was no exception.

Listening Test #3 - Versus The OII MKI

Comparing the SR-009 and OII MKI directly against each other across multiple genres of music was both educational and introspective—it repeatedly made me ask myself which headphone sounded more accurate, which one was more rewarding & satisfying to listen to, and most importantly, which was better, if one could be called better than the other.

I ended up concluding that the OII MKI essentially beat the pants off the SR-009. The SR-009 was certainly a very strong contender though, and I'd affirm that it's definitely among the best-sounding headphones overall of any type. Easily among the Top 5 that I've heard to date. I might as well list my Top 5 for reference (not necessarily in order, as I don't "rank" headphones per se): (1) Stax OII MKI, (2) Sony Qualia 010, (3) Grado HP1000, (4) JH Audio JH13, and now (5) Stax SR-009. Moreover, I'd call the SR-009 probably one of the most technically-amazing headphones that I've heard to date, after the Qualia 010. Very clean- & clear-sounding, inherently fast (i.e., impulse response), and appropriately diffuse-sounding with very good separation between layers/instruments.

But the SR-009 wasn't really that awesome next to the OII MKI. The most notable difference to me was the lack of "magic" or x-factor like the OII has. The OII was also simply more natural- & authentic-sounding in the mid-range with a fuller sound and heavier, more physical-feeling bass. Or to put it another way, the OII had more impactful drums & bass lines, heavier guitars, and more vocal presence. This made the OII MKI seem like a more musically versatile headphone, as it played electric & synthesized music very well too. I thought the SR-009 was at its best with primarily acoustic, laid-back types of music—classical, jazz, folk, etc. However, it didn't fare as well with trip-hop, pop/rock, & metal, as it lacked the OII's mid-range, mid-bass, & bass spark to really make them come alive.

I also felt that the SR-009's imaging was a step down from the OII MKI's. Granted, it did have a wide, deep soundstage that felt more 3D due to the increased z-axis depth and some added height as well, but it also felt narrower than the OII. More importantly, the SR-009 did not have clearly-delineated walls in the soundstage and felt very flat & vapid. Or in other words, it had a very limited ability to clearly render reverberation and the sense of sound waves reflecting throughout the virtual soundstage. It was because of this aspect that despite having a smaller soundstage, the OII actually sounded "bigger" and more "expansive" than the SR-009, as it allowed sound to really fill up "everywhere" to the point of hitting the walls, so to speak.

Needless to say, this affected "scale" as well, as the SR-009 never quite sounded as "big" as the OII MKI and consistently failed to deliver a sweeping "wall of sound" that wrapped from one end of the soundstage to the other. The SR-009's idea of a "wall of sound" felt like a small, translucent wall instead that was just sad in comparison.

Tube Rolling & Gain/Volume

I briefly tried the Genalex Gold Lion KT77s on the SR-009 and would have to say that these tubes had a better effect on the SR-009 than the OII MKI. I've found that these tubes add bass impact and more body to the mid-range, which was a better result on the SR-009 than the OII MKI. The KT77s didn't rectify the SR-009's sonic issues for me though, but there was still an appreciable added difference with them.

The issue of gain is one that's been reported by other SR-009/BHSE owners, but I didn't run into this issue myself, as my specific BHSE has a lower gain than normal due to its configuration of Stax Pro + Normal jacks. This made my BHSE well-suited for driving the SR-009, as I could achieve just about any volume that I wanted, even from the 4V RMS balanced output of my source.

On the subject of sensitivity, I found that the SR-009 required about 3 less steps on my DACT-configured BHSE to achieve approximately the same volume as the OII MKI. I also tried turning up the volume to moderately high levels on the SR-009 to see how it would respond and it continued to sound very good even at high levels. No issues or detractions that I can report from high volume.


The SR-009 ended up being about as underwhelming & disappointing to me as it is expensive, and I'd have to dissent with the prevalent opinion among other Head-Fiers that it's one of the best headphones currently in production, electrostatic or not. I saw it as essentially a step backwards from the OII MKI—enough that I'd degrade its ranking to "above average" from the OII MKI's "excellent".

I view the OII MKI as the superior headphone and recommend it instead for anyone truly seeking a serious & honest high-end electrostatic setup.

For reference, these are some other headphones that I rank as "above average"—Audeze LCD-3, Beyerdynamic T1, Grado HP1000, Sennheiser HD800, Shure SRH1840, and Stax SR-507. However, just because I classify the SR-009 as being "above average" doesn't mean I think it actually deserves the company of those other headphones, as I think it's better than all of them. It's just that it ultimately fell short of being "excellent" to me, as did those other headphones. As might be inferred, there's a lot of subjective gray area within my rankings, which is intentional—I've historically avoided numerically ranking gear for numerous reasons, not the least of which is that it's extremely subjective and prone to misinterpretation. The only reason I have a ranking scale that goes from "atrocious" to "excellent" is to help identify equipment that truly stands out from the rest. "Average" for me includes headphones like the AKG K2xx/K70x, most of the Audio-Technica woodies, most of the Grado models made under John Grado, Sennheiser HD6xx, etc—i.e., most of the venerable classics that sound very good to the highest cross-section of Head-Fiers with mid-level gear & experience. It's easy for most headphones to fall under "average" to me for this reason—there aren't very many that are below-average or atrocious to me. "Below-average" to me includes the Audio-Technica ATH-ES7 and Sennheiser HD419 (both of which I own—yes, I'm critical even of the headphones that I own!) and the new Denon AH-D7100, for example. Finally, "atrocious" includes Apple iBuds. Enough said?

My ranking system is in place primarily for two reasons: (1) to help set reasonable expectations for newbie or mid-level Head-Fiers seeking to upgrade, (2) to help equalize the field among the high-end options for high-level Head-Fiers seeking to sidegrade or upgrade—i.e., someone who's heard as much dynamic gear as I have who thinks the HD800 is one of the best headphones available might come to the conclusion that he might not need to get an SR-009 or the BHSE. Or someone who already owns the SR-009 and BHSE might conclude that he needs to try an SR-007. Or conversely, someone who owns the OII MKI and BHSE might conclude that he doesn't need to try the SR-009. ;)

Related Reading

- Stax SR-007 & HeadAmp Blue Hawaii SE review & story: http://www.head-fi.org/t/598589/review-story-stax-sr-007-headamp-blue-hawaii-se
- Audeze LCD-3 mini-review: http://www.head-fi.org/products/audeze-lcd3-planar-magnetic-headphone/reviews/10298
- Beyerdynamic T1 review: http://www.head-fi.org/products/beyerdynamic-tesla-t1/reviews/10295

- Sennheiser HD800 review: http://www.head-fi.org/products/sennheiser-hd-800-headphones/reviews/10294

Addendum - Review Notes

My review notes are included here in their own section for convenience. These provide specific detailed info not included in the review. Notes start below the asterisks.

009 not the electrostatic equivalent of Qualia, as previously thought.

009 imaging more divergent/diffuse. More front- & center-loaded, not as close & wide as 007. Almost like a shell, but large. Instrument positioning further away, yet lacks the "air" of the 007 that allows details like reflected sound to be heard on it. Reflected sound not very apparent on 009. Room acoustics in general not as clear on 009 as on 007.


Spatially-larger imaging on 009—narrower width than 007, but more depth & height, more of a 3D-like effect. More "air" in the acoustics. Somewhat HD800-like, but not as much as HD800.

Deeper mids & bass on 007—more of a heavier, almost physical sound, for a stat that is (dynamics tend to sound more physical than stats). 009 lighter- or thinner-sounding with more treble quantity, but not as much as Qualia (or even the HD800). Relative to 007, not absolute.

SR-007 consistently more percussive sounding (harder-sounding pops).

Despite lack of stats sounding "direct" in general, 007 sounds more direct & assertive than 009. 009 more laid-back and passive.

Reverb more pronounced on 007, allows ambient electronica to sound more "space-filling" than on 009 where it sounds vapid. Sounds "bigger" on 007 due to clearly-delineated walls. No clear "walls" on 009. 009 like HD800 in this aspect—neither has walls, they just sound open & empty yet flat at the same time.

Violin tone more natural/authentic on 007, more wispy & ghostly on 009. 009 also reduces "unified body" of 1st violin section—too much of an individual-violins effect, not enough of the group effect. 007 renders a properly intact 1st violin section. 007 also tends to put the listener position at the conductor; 009 puts the listener in the audience row. 007 also renders more detail in violin-bowing technique—speed, inflection, etc.

009 loses the 007's magic/x-factor—the intensity, the live-performance surrealistic immersion. 009 slides back to more of a pre-recorded music feel. 007 has a more tactile/visceral sound, esp in bass/mids. 007 has more depth/richness/fullness in mids than 009—i.e., violins & vocals "swell" more on 007. 007 has more "fill" factor. 007 capable of a more powerful/intense sound.

007's smaller soundstage and mids better-suited for jazz. 007 "brassier" and "reedier" sounding than 009, which loses those elements.

Piano semi-plinky on 009—lack of depth/weight to notes. Not enough "weight" to various instruments on jazz recordings on 009, notably piano & brass (Dave Brubeck, Steve Kuhn). A440 that should "pound" on Brubeck's Time Out LE doesn't really pound on 009. More integrated imaging on 007 better for jazz, puts listener more in with the group (a la Grado HP1000, but not as much).

Julia Fischer Bach Concertos track #8: 007 captures a more beautiful, radiating, pure tone on Fischer's violin than 009. The almost heat-shimmering radiance not there on 009. 007 also has more of a chamber-orchestra feel than 009 in terms of the imaging, like you're in with the orchestra, practically right next to Fischer, which is probably more accurate. 009 has more of a sitting-away-from-the-orchestra feel. 007 does have smoother treble, sort of negatively affects edginess of harpsichord specifically, but nothing that overly detracts from it.

CD albums used for review:
- Alison Krauss & Union Station - So Long So Wrong, Paper Airplane
- Carlos Kleiber & VPO - Beethoven Symphonies 5 & 7
- Dave Brubeck - Time Out [Legacy Edition]
- Goldfrapp - Black Cherry
- Helloween - 7 Sinners
- In Flames - The Jester Race
- Julia Fischer - Bach Concertos
- Lee Morgan - Tom Cat [AudioWave/Blue Note XRCD]
- Massive Attack - Blue Lines, Mezzanine
- Megadeth - Countdown To Extinction [Mobile Fidelity Sound Lab]
- Meshuggah - Chaosphere
- Nicola Benedetti - Fantasie
- Orbital - Snivilisation, The Middle of Nowhere
- Porcupine Tree - In Absentia
- Radiohead - OK Computer
- Sierra Hull - Secrets, Daybreak
- The Crystal Method - Vegas [2007 Deluxe Edition]
- Tord Gustavsen - Changing Places
- Trifonic - Emergence

1 Comment:

Value is bad on this headphones I agree too.
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