My (waaay too long) review of the Stax SR-009S

Brief introduction

I’ve had the Stax SR-009S for about a month now, listening approximately 5 hours a day to a large variety of music. This will be a very long and detailed review outlining my exact stance on what the 009S is to the best of my ability. For the first time I will also cover EQ, both what I percieve as being good/sufficient myself and u/oratory1990’s harman target compensation EQ.

As a quick disclaimer, this is the only headphone of this caliber I’ve ever listened to for an extended period of time. Any queries about how it compares to LCD-4, Utopia, 1266/Diana, Susvara et cetera would have to be answered by someone with more experience A-Bing those headphones. Due to my limited amount of headphone inventory currently there will be no detailed comparisons.

There will be a TL;DR at the end of each breakdown for the people who aren’t interested in reading this endless ramble. Just scroll to the bottom 😊

An intro to the SR-009S (packaging and build quality)

The SR-009S is the (co)flagship in Japanese company Stax’ lineup, a follow up to the SR-009 released 2011 and the 5th installment in the omega series (depending on how you count). The Stax philosophy is to make electrostatic transducers that are as transparent as possible. Through logical deduction you can say that this is in Stax’ opinion the most transparent headphone they have ever made.

The SR-009S clocks in at over 4 000 dollars, and is not exactly a small purchase. For this price you get a very nice wooden box Filled with foam that houses the headphone. This box has protective benefits according to the supplied owners manual. It supposedly keeps humidity out (which is bad for the antistatic coating used on the membranes) and works well as a temperature regulator. I have kept my 009S in this box when not in use just like Stax recommends, a bonus is the fact that the headphones start smelling of wood after they lie in the box for some time.

I have only 2 complaints about the box, the first one is that the wood used (Paulownia) is so ridiculously soft that even when shipped with great care it got a slight dent in the corner. Doesn’t matter much for practical use but annoying nonetheless. The second annoyance about the box is the text. Apparently Stax changed the design on the wooden box right around the SR-009S release. On this box the text is printed on top of the lacquer but it is way too fragile. Both the A and X in the Stax logo are looking rough already and I’ve only touched those when dusting off the top of the box.

Build quality is similar to the box, very good but not without fault. Earpads are fantastic quality, no complaints on that. The machined aluminum cups are also great and feel sturdy. Internal structure is typical of Stax and naturally quite a bit ahead of most other manufacturers. Headpad feels great and is really huge. About 90-95% of it touches my head at all times, the distribution is just fantastic. Cable is the same old ribbon cable found in all Stax, except it is a copper-silver hybrid, for those of you that care about that. The strain relief on the cable appears to be very good, seems like Stax learned from Omega and 007 MK1.

Once again, 2 complaints. The first one is obvious; the headband arc is completely out of place on this kind of product. They tacked on the same cheap plastic arc that is used on the L500 and L700. The arc gives very nice clamp force and is sturdy enough even for my very large head, but it still feels very out of place on a 4 000 dollar headphone. The second complaint is the earpad mounting, what kind of absolute buffoon designed this piece of shit? It’s basically a plate that is screwed on with the pads fastened to it. This makes swapping or cleaning the pads a royal pain in the ass. I’d rather just have a lip ring like most headphones.

TL;DR Build quality and packaging

It’s very good, not much to complain about. Wood box could be better, earpad attachment sucks. Headband is cheap plastic ☹ Smells very nice when you open it.


The tonality of the SR-009S is something I had a very hard time explaining. There are only 2 real issues which I feel need fixing, one very simple and obvious one and another one that took me a long time to understand. When you first put the SR-009S on your head it becomes apparent that this is a headphone that has no horribly offensive tonality issues. Things simply sound pretty right. There is no excess treble, but in no way is it subdued either. Some will maybe find lower midtreble slightly recessed, but I think most people will consider it to be just right. Midrange is pretty even, but naturally has some 1K emphasis that is present in basically every Stax. Some might also find there is a lack of bass, while others might find it just right.


Bass is sort of an oddball on the SR-009S, on one hand it is definitely there and extension is fantastic, being close to flat into infrasound. Ultimately bass was and continued to be my biggest issue with the SR-009S. Because while extension is good and it keeps a very straight line from 100Hz-20Hz I still feel like the general level is too little compared to the rest of the spectrum. I feel like it is even less bass than DF flat, which means that most listeners are definitely going to have issues with it. If bass was just 3dB more I think it would be perfectly adequate (coming from someone who thinks harman target is slightly too bassy).

Bass impact on most electrostatics is quite weak. Couple this with the bass deficiency found in SR-009S and you have a good-ol zero-impact headphone. Punch, which to me feels like it is closely related to the transient response of the headphone, is of course great. Texture on the bass is amazing. You hear all the stuff going on in different layers so to speak. In some music you might realize there is some kind of added reverb in certain bass notes, or the rolling of the drumskin rather than just the drum itself. Really good stuff and a trait I find drags me toward electrostatics.


Most information in music happens in the midrange, and for me nothing beats some good electrostatic midrange. The SR-009S has a slightly forward midrange, some might find it slightly shouty but it’s nothing bad. Other impressions I’ve seen say that Stax made the lower midrange thicker in the SR-009S vs the SR-009, which I think is a good call. It has a lot of coherency throughout the midrange, although it serves as perhaps too stark of a contrast to the somewhat lacking bass. The SR-009S is less forward than most lambdas I’ve heard in the upper mids. Although it definitely has some elevation going on around 3k.

Timbre and tone is great, realism of voices and instruments is great. Listen to anything by Agnes Obel for example and it is very obvious that this is something the midrange gets right. FWIW I don’t have any problems with «plastic timbre» that some people say they get from electrostats, so take this with a grain of salt if you hate them.

The second issue I mentioned earlier on is specifically somewhere around the upper midrange. The problem is that there is a recession somewhere right around 2k which makes certain female vocals sound a little soft. I think this wouldn’t be an issue if only 1k or only 3k had some elevation, but with both of these areas being slightly above neutral it is obvious this is not quite in line with the rest of the response. This was more of a subconscious thing and took me way longer than I’d like to admit the figure out. I had to do sine sweeps to find out what specifically bothered me here. I want everyone to also note that this should be within the area where pinna interaction has an effect on the response, so not everyone might have any issues with this.

Other than this the midrange has this beautifull transparency to it that I feel only electrostats really convey. The sound does not feel confined to the drivers themselves. The sound practically exists on another plane than the drivers do, with dynamics and planars I experience that I often «hear» the drivers themselves, while electrostats give me the feeling that it’s just the music appearing out of thin air. I think u/mcmadface put it very well when talking about the SR-009; it’s like putting on a pair of glasses with no lenses.


Treble of electrostatics in general is very, very enjoyable as it conveys a similar experience of transparency that you get in the midrange. I’ve found that electrostatics are the headphones that really get treble «right» even if they sometimes have a wobbly response. The SR-009S is no outlier in this aspect, providing crystal clear and well extended treble with very few dips and no real peaks. When doing sine sweeps there is a very obvious drop at 6KHz, but it’s such a high-Q drop that I can’t find it affecting my listening experience at all.

There’s a lot of layering and detail in the treble, everything comes through to the listener clearly. I don’t have a whole lot more to say about the treble. It’s an electrostat with a not fucked up frequency response, so naturally this is the result. Due to the slight recession in the midtreble the headphone is also free of any sibilance.

TL;DR tonality

Bass could stand to have more quanity, extension and quality very good. Midrange extremely good with just one small slightly weird dip at about 2k, very realistic. Treble is great and mostly even, 6KHz drop that isn’t noticeable in normal listening.

Other sound

Here I will be covering other aspects of sound such as transient response, soundstage and imaging. The SR-009S does generally well across the board, and unlike the tonality and build I don’t have a lot of pet peeves here.

Soundstage and imaging

Soundstage is great, it is expansive in all directions and has the deepest soundstage I’ve ever heard, which pleases me greatly as depth is something most headphones fall short on. In terms of absolute percieved size it is not the biggest I’ve ever heard but it is still very close. I think the main thing the SR-009S falls short on is the width of the soundstage, which honestly feels a little underwhelming compared to depth and height. I’d go as far as saying most lambdas can challenge it as an equal here.

Soundstage means little without proper imaging to back it up, and the SR-009S has it in spades. It sounds extremely precise, and thanks to the great layering you can really hear everything going on come through clearly from their own spot in the soundstage. Now, while imaging is great, I personally feel that imaging is good enough on certain headphones that it can’t really get any better. I just can’t percieve it improving in any way because it is so extremely pin-point accurate, the SR-009S is one of the headphones that make me feel this way. If the imaging is already «perfect» (to my ears) how would one improve on it?

Layering and separation

I’ve briefly mentioned parts of this throughout this review, and I’m sure most of you will be able to guess exactly what I’m gonna say. The layering and separation is just out of this world good. There is so much detail coming through clearly because every sounds feels like it happens in its own little plane of existence. It really doesn’t feel like the mushy soup of sounds most headphones present to you, rather it is like having an entire orchestra playing in front of you, but there is almost no blending of the sound coming from each instrument. Some might call this a bad thing but I think it is awesome because it really allows me to hear what goes on in demanding recordings.

Another point to the layering and separation is how great the bass blends with the rest of the audio spectrum. In most electronic music or pop where there is some sort of constant droning or a bassline the bass stays somewhat in the background, while all other sounds come out clearly like they are slightly in front of the bass, this is not just because of the lacking bass, because even with EQ I’m experiencing the same thing. Comparing this to most other headphones the bass often feels like it gets smashed together with the rest of the audio spectrum and then it gets harder to hear what’s going on in both bass and midrange/treble.

Transient response

The praise won’t stop coming any time soon. Most people know that electrostatics have excellent transient response and are percieved as very «fast» sounding. The SR-009S is of course no exception and has just the same level of transient response that I feel I find in every electrostatic. You can play some of the fastest and dirtiest metal imaginable and the SR-009S (or any Stax for that matter) will not break a sweat. Some might find this unnatural to begin with, and I believe this is the reason a lot of people don’t like electrostats, to me this is heaven though, YMMV.


I’ve always thought detail comes down to everything else about the headphone being great, I’ve never heard a headphone with absolutely fucked frequency response sound detailed for example, and I blame that on auditory masking, same goes for things like layering and separation as well as transient response. Basically, since the Stax does well in all these areas I find it great at extracting detail from recordings and making it obvious.

TL;DR sound (other)

The techincal prowess of the SR-009S is a marvel to experience. Any metric I can think of I feel like it truly excels, I don’t think anyone’s gonna complain about SR-009S soundstage, or imaging, or layering… You get the gist.


Comfort is very important and the SR-009S has it in spades. I have a pretty big head and use the headband on either 7 or 8 out of 10 notches depending on how tight of a fit I want. Clamp is great, and distributes the weight evenly around the ears. Earpads are very soft and both the leather and fake leather feels great to the touch. Headband is truly the standout here. As mentioned earlier about 90-95% of it touches my head. The area of distribution is huge. The headphone weighs almost half a kilogram but I’ve sat with it on for up to 12 hours with zero issues.

The headphones don’t have the best breathability I’ve ever come across but it is certainly fine, just not a headphone I would use in the middle of the day during summer when there are alternatives with velour, suede or alcantara present. I could see the fit being slightly awkward for people with coneheads, but even then I don’t think there should be any huge issues with fitting the SR-009S on your head. My small headed friend u/plussrep has the SR-009 and I’m sure he would be willing to tell you about his experience with the fit of the headphone.

TL;DR Comfort

Comfort is good, should fit basically anyone, even my bigheaded fellows.

EQ (Oratory1990/Harman target)

Most headphones benefit from EQ, but I don’t think I’ve ever tried a headphone that benefits as much as the SR-009S with as little adjustment needed. Bump 2k about 3dB and bass about 3-4dB and this headphone is quite close to perfect for me. Now this is personal opinion so I will rather just talk through u/oratory1990’s compensation curve that turns the SR-009S towards the harman target.

I think the harman EQ is great, and by all means a benefit over stock SR-009S. The bass goes from being somewhat underwhelming to being slightly overwhelming for my taste, but it should be right at home with most people. It takes up the low-mid treble quite a bit which gives a nice compensation for the large dip around 6KHz. This dip didn’t bother me but some extra midtreble in general certainly didn’t hurt although it gets slightly more fatiguing on certain music.

Harman curve also has slightly too little midrange for my taste, I find the somewhat forward nature of the SR-009S just about perfect, coupled with slightly more bass than I’d like and it gets very close to feeling like a slight V-shape to me. Nothing bad though, and certainly better overall than stock by virtue of bass alone.

To me the EQ provided by u/oratory1990 gave a great slate to start working on. Shave off a little bit of bass and maybe tune up the mids a little etc. but this is of course highly personal and something you’ll have to figure out yourself, perhaps u/oratory1990’s curve is perfect to you. Bottom line is that you definitely should at least try to EQ the SR-009S, I can’t guarantee that you specifically will like it, but 90% of people probably will.


EQ good, try it.


The SR-009S is without a doubt a world-class headphone. It does some things so incredibly well that I could weep tears of joy as a Stax fanboy. With that being said, it has some evident tonality issues, and what feels like a few minor oversights that I would not expect in a product of this caliber. The price is also a tough pill to swallow, so much in fact, that it has to go. I got it as quite a decent deal, but even so that is simply not quite enough. Because while I can afford it, I ask myself if I should afford it, the answer is no and so I will be selling. The greatest compliment I can give the SR-009S is that I genuinely enjoyed every second I spent listening to it, and I'll be very sad to see it go.


Maybe a SR-007 is in the cards for me? Hmm...


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