Too Long Didn't Read Version: <insert endless stream of superlatives> How can a headphone sound so realistic? How can a headphone so clearly have the best transparency, detail, bass, mids, AND treble by far of any headphone I've used? Ah, one of few headphones with a sound stage and imaging that sounds as if it was trickled down from excellent loudspeakers. As close to perfection as headphones will ever get I think.
If there's any compromise in the audio chain though, or if I have a laid back DAC, the magic is gone for me... the only things I dislike about the SR-009 are the top headband being plastic, and how annoying and expensive it is to get the most out of it, because if you don't get the most out of it (more or less, not saying you need a DIY-T2 amp) then don't bother with it. And you can have a no compromise system but still have a dull sounding SR-009 if something is just a sonic mismatch like the DAC or interconnects.
Full Version:
The Stax SR-009 is a legendary headphone. Tyll's "Comparing World-Class Headphones" review at Innerfidelity opened many peoples' eyes to it, including mine. When I began my hi-fi headphone journey, I just knew the SR-009 was where I had to end up. Since opening this can of worms, I have owned the following open back flagships or former flagships:
- Stax SR-007A
- Audeze LCD-4
- LFF Code-6 (modded HiFiMan HE-6)
On numerous occasions I have also listened to the HiFiMan HE1000, Sennheiser HD 800 S, and Sennheiser HD 800 in quiet environments, and auditioned the Sennheiser HE 1 back when Sennheiser had audition spots for them in NYC. I have also listened to the Abyss AB-1266, entire Audeze LCD fazor lineup, Focal Utopia, and Beyerdynamic T1 Gen 1 in louder environments (not very meaningful listening). Other noteworthy headphones I have owned are listed in my profile.
I really wanted to write this review, more than any other headphone since with the Stax SR-009 and Mjolnir Audio KGSSHV Carbon I have finally reached an end game. With the Stax SR-009, I have perhaps reached the end of my headphone journey (not headphone gear as a whole, but primary at-home listening headphone journey). I don't foresee any major improvements beyond this point, while the SR-009 is a major improvement over every other headphone I have ever owned or listened to... in just about every way.
Before we get started, I must emphasize that
high end Stax headphones (SR-007, SR-009, SR-009S) scale more with higher end amplification, DACs, and analog interconnects than any dynamic or planar magnetic headphone. Amp and DAC and interconnects each make a MASSIVE difference. This is an extremely positive review as you're about to see, but it would NOT have been nearly this positive if my DAC was only the Chord Mojo, even with the same amp. Likewise, it wouldn't have been this positive if my amp was a KGSS regardless of DAC. Nor would it have been this positive with cheap generic interconnects.
Going from a KGSS to a KGSSHV Carbon with an SR-007/SR-009/SR-009S makes a bigger difference than going from a Schiit Magni to a HeadAmp GS-X Mk2 with a HiFiMan HE1000 or any Audeze. And going from a Chord Mojo to a Hugo 2 with an excellent Stax system is a gigantic upgrade in every possible way.
Believe it or not, going from cheap generic interconnects like Mediabridge, to Kimber Kable Hero interconnects with this system is a bigger upgrade than most DAC upgrades with ANY non-electrostatic system, and many amp upgrades to. For example, it is a bigger upgrade than going from a Chord Mojo to a Hugo 2 with a Mjolnir Audio Pure BiPolar and Audeze LCD-4 or LFF Code-6, and it is a bigger upgrade than going from a Schiit Lyr 3 to a Mjolnir Audio Pure BiPolar with an Audeze LCD-4. Hard to believe, right?
Another review here says that the SR-009 has less dynamic punch than today's offerings like the Focal Utopia. He mentioned his amp was a KGST (didn't see which DAC). Well, I use a KGSSHV Carbon, I've listened to the Utopia and owned the Audeze LCD-4 with top tier amplification, all of this with a Chord Hugo 2, and I can confirm that statement is a false generalization.
The SR-009 + KGSSHV Carbon + Chord Hugo 2 has the most dynamic punch I've ever heard in a headphone overall, and nothing else comes close. Does this have the most bass impact? Not quite, though more than any open back dynamic headphone I have come across despite not having that annoying mid bass hump. But the attack, transient response, and lightning quick decay, and full bodied/impactful instruments that non-electrostats can only dream of, is what causes this amazing sense of dynamic punch that no other headphone has given me.
But when I substitute my Chord Mojo for the Hugo 2, most of that goes away and indeed the SR-009 starts to lack punch and dynamics. Moral of the story = don't cheap out on any system component!
I can break it down like this:
- Any non-electrostatic headphone system = veiled, muffled artificial headphone experienced
- Chord Mojo + KGSSHV Carbon + Stax SR-009 = Noticeably better than non-electrostats, but still a veiled artificial headphone experience
- Chord Hugo 2 + KGSSHV Carbon + Stax SR-009 = No longer a headphone system but a clear open window into the music (and I'm sure if you swap the Carbon with a KGSS or any Stax amp then you're back to a veiled artificial headphone experience)
Moral of the story is,
if you are building a Stax SR-007/SR-009/SR-009S system, don't cheap out on anything. Except perhaps power cables, I don't even hear a difference between generic ones and Pangea ones anyway.
Packaging
The SR-009 comes in a rather mundane but clearly labeled box. Inside however is a wooden case; not the most protective, I much prefer the Seahorse case ZMF uses or the similar case employed by the Audeze LCD-4 (best included case I have ever come across), heck I also prefer the SR-007's metal case, but this is nice. I store the headphone in it when I don't plan to use it for days. Otherwise, it sits on my Stax stand underneath an electrostatic bag for protection.
Build Quality and Comfort
Somewhat disappointing in all honesty. The top headband is plastic; one could abuse it and break it. The adjusting slides for the inner headband are also plastic. Surprisingly, the build quality of modern day HiFiMan flagships (formerly HE1000, currently Susvara for planar line and Shangri La for electrostatic) employs a better built headphone body and adjusting slides which are all metal. So... I'd really like these parts to be metal. Or just go with the SR-007's headband.
On the bright side, the inner headband and ear pads are lambskin leather as far as I know. Soft, comfortable, no odd smell, and should last a long time.
The yokes and cups are very solid metal and the cups have a large swivel range. The cable is long and unfortunately not removable, but supposedly of very high quality. While the build quality isn't as solid as I'd like (the SR-007 is also better to me, no plastic), the comfort is top tier. People talk all day long about the HD 800/HD 800 S's comfort, but really the ultimate combination for comfort is adjustable suspension headband with a soft leather inner headband, and large, thick, soft leather ear pads that don't touch your ears at all. Considering this, the SR-009's pads are not very thick, but your ears don't touch anything hard on the inside (they barely touch anything in fact) and the clamp isn't hard so it's alright. Exquisite, flawless comfort.
Adjustment range for the SR-009 could be more. I use it on the largest size and plenty of people have larger heads than me. Poor NBA and NFL players... they won't get to enjoy the SR-009/SR-009S? Though they can afford full range electrostatic loudspeakers so not much is lost for them!
Sound Quality
This is the part that matters most and it is where the SR-009 excels the most. The Stax SR-009 is utterly unlike any other headphone I've listened to. Some traces of its excellence exists in the SR-007, but it is a totally different animal. I remain in disbelief to this day how shockingly transparent, detailed, and real it sounds.
I have seen many headphone enthusiasts go through various dynamic and planar magnetic flagships, and never touch Stax. What a mistake. Top tier Stax systems (SR-007, perhaps SR-Omega, and especially SR-009 and SR-009S, powered by at least a well built KGSSHV) make all other headphones sound relatively veiled/muffled and fake. Almost like the others are toys. This is coming from someone who at least anticipated favoring a planar magnetic headphone for rap, but no, I ended up favoring the SR-009 for every genre and it's not even close at all. Line up every headphone I've owned, and I would never reach for another if my goal was musical enjoyment. Only the SR-009. Granted, I never had a beefy enough amplifier for my SR-007A (only a China clone KGSS fixed up by Birgir).
Compared to all non-electrostatic headphone systems, the SR-009 + KGSSHV Carbon or Grounded Grid or Blue Hawaii SE or Megatron or DIY-T2 (and probably a regular KGSSHV as well but to a lesser extent) will reveal MANY new sounds in almost all music that other headphone systems are not good enough to reveal. This is one of the most incredible attributes about the SR-009. The transparency is just almost unrivaled; as I said, almost all other headphones are veiled in comparison, including all dynamics and planars
The SR-009 with a good enough amp will "take you there" and I am convinced only an electrostatic system can do this, since no planar or dynamic system can. Not the Focal Utopia. Nothing from Sennheiser, no HiFiMan planar (and I personally doubt their electrostats too), nor Audeze. They don't come close whatsoever.
It's actually difficult to describe the SR-009's sound signature. You will see people call it very neutral, or perhaps a bit bright, but that's misleading. The sound signature is totally unlike any non-electrostatic headphone. Contrary to what I see written I do NOT believe it is a poor matchup for bad recordings/poorly mastered music. I think the SR-009 makes ALL music sound better, whether vinyl or digital, great quality or not. For crappy MP3s it still reveals sounds I never heard before, and good ones at that, while making the music more transparent and realistic than ever. Such that the only other headphones I have any measurable interest in listening to are the SR-009S and to a much lesser degree SR-Omega (mostly curiosity since I'm entirely convinced the SR-009 and SR-009S rule over all).
So I will describe the sound signature in a nutshell as... mostly neutral but with an upward tilt, wonderfully extended in both directions (spoiler alert: the best bass, mids, AND treble of any headphone I've listened to, and remember I've owned the Audeze LCD-4 and have experience with all kinds), full bodied beyond what any non-electrostatic headphone can achieve, impactful with phenomenal spatialization and sound stage and imaging, the fastest headphone I've ever listened to by far (most realistic decay and transient response I've encountered) which combined with the very impressive bass slam and unmatched treble performance is why I find it has the most dynamic punch of any headphone system I have used.
To me the SR-009 is upward tilted in a way that allows its upper frequencies to create a clear transparent window into the music like nothing I've ever heard before, and this is without recessing any of the lower frequencies. You have not heard full bodied headphone treble worthy of being called authentic unless you've listened to a properly driven top tier Stax headphone.
A well driven SR-009 creates so much more body, weight, impact to nearly every single instrument in existence, compared to all non-electrostatic headphones. The only exceptions are certain drums which the best planars like the LCD-4 can match or surpass in impact, and match in body/weight. But the SR-009's bass is far more transparent and detailed than any planar, such that I prefer its bass to any planar by clear margins.
Every frequency range, from sub-bass to upper treble and everything in between, is FAR more transparent and detailed and realistic than every headphone I have heard to date (though again, never properly amped my SR-007A). Of all headphones I've listened to, only the SR-009 has perfected the upper mids to lower treble transition. This perfection right here, this frequency range, is responsible for making nearly every other headphone sound veiled and fake and even toyish in comparison, especially non-electrostats.
But the SR-009, SR-009S, and SR-007 are some of the most amp dependent headphones out there. For example, I have also listened to the SR-009 out of the Woo Audio WES, and it was just veiled and obscured compared to a Blue Hawaii SE or KGSSHV Carbon. To get the most out of these headphones, you do need a very expensive amplifier like my Mjolnir Audio KGSSHV Carbon. But even then, my SR-007A + KGSS was more transparent than any non-electrostatic headphone, with noticeably more full bodied and realistic treble than any non-electrostatic headphone, but still absolutely nothing compared to how it sounds with a top tier amp (I have used the SR-007Mk1 with a HeadAmp Blue Hawaii SE on several occasions).
But when I use the Chord Mojo as the DAC instead of the Hugo 2, a LOT of this magic is gone. Much of that transparency, resolution, impact, airiness, sound stage, and imaging gets flushed down the drain. It's still far more transparent than any non-electrostatic system I've listened to but yeah... this is kind of lame haha.
Let's try to break it down and get more specific here.
Bass
The most breathtakingly convincing bass presentation I have ever heard in a headphone. Remember, I've owned the Audeze LCD-4. Compared to that, the SR-009's bass transparency and detail are as if it opens up a window, revealing a new dimension to bass that not even the best planars can reveal.
The LCD-4 does have much heavier bass presence creating a thicker sound which some might prefer (bass is always distinctly present during all sounds), no doubt about that, and it can slam a bit harder as well, and it extends deeper, but it's still missing a dimension of clarity and details compared to the SR-009's bass. Percussive instruments even sound so much more real on the SR-009 than any planar. One of the most impressive attributes of bass performance with the SR-009 + KGSSHV Carbon is the portrayal of very fast drums on heavy metal songs. The SR-009 just annihilates all non-electrostatic headphone systems here.
Using the bass sweep test at
this website, the SR-009 only seems to extend down to around 20 Hz while great planars can go down to around 10 Hz, but that's no big deal in practice since music almost never goes this deep. Believe me, I care a ton for bass extension. I listen to rap and heavy rock and metal, and the SR-009's bass is by far my favorite of any headphone I've listened to. It even has more bass slam than most headphones, more than my previous LFF Code-6 (modded HiFiMan HE-6), more than the HE1000/HE1000 V2 so probably more than any HiFiMan headphone that ever existed for reference.
There is a stereotype about electrostatic headphones having less bass than dynamic headphones or something. The main source for this is that dynamic headphones naturally have a mid-bass hump... as well as sub-bass rolloff which is another story. Well, I cannot name a single dynamic open back headphone with more bass slam than the SR-009 on an amp like the KGSSHV Carbon, nor can I name a single dynamic open back headphone with a single advantage in bass performance vs the SR-009. Then again, the only dynamic open back headphones I've listened to with
any advantage over the SR-009 are the Sennheiser HD 800 and HD 800 S in imaging performance, but the SR-009 is close enough for me. But I digress.
Mids
Magical. Vocalists are super clear and brought to the forefront, but at the same time you can't help but notice incredible sound staging and imaging, so many layers to music, perfect instrument separation.
The most impressive thing about the mids to me is the body, weight, and impact to every instrument. Of course this isn't limited to the mids, but every instrument in every frequency range has a fullness and impact to it that I've never heard before. I've never heard such full, clear/transparent, and real sounding strings or pianos or horns before for example. Not even close. These instruments and many others sound tiny, veiled, obscured, and fake in comparison, and again the difference is massive.
There is a slight upper mid range hump visible on frequency graphs, which to my ears manifests as a slight upward tilt that gives more body/weight/fullness to the upper mids to treble transition area, where so many headphones sound weak/frail and fake in comparison. But this upward tilt isn't to everyone's preference and I am really curious how the SR-009S sounds which supposedly doesn't have this. But as it stands, I have no issue with any mid range region.
Treble
Of all frequency regions, the SR-009's treble is the most impressive to me, because of how much better its treble is than every other headphone system I've owned. It doesn't overshadow the rest of the spectrum, but the SR-009's treble doesn't hold back at all... yet it is the cleanest, clearest, most full bodied, most realistic treble I've ever heard by far and is largely responsible for this headphone sounding so transparent, detailed, and real. Every non-electrostatic headphone's treble sounds so thin and one note compared to this. Words really do not suffice, you have to hear a properly driven SR-009 in a quiet environment. This improvement will jump right out at you immediately.
Likewise, the upper mids to lower treble transition is like no other headphone I've heard before. It creates a whole new dimension of realism, transparency, detail. I've also never heard such "airy" sound from a headphone before. This airy factor seems to improve imaging and perceived realism significantly.
I was surprised to 'only' hear the SR-009's treble extend to 20 KHz in the treble sweep test located at this website. My previous LFF Code-6 (modded HiFiMan HE-6) reached 21 KHz, so it's not my ears. So the Code-6 has the most treble extension I've ever heard, SR-009 is #2. But in practice this is meaningless... what music goes beyond 20 KHz?
With all of that being said, the SR-009 will always be too upper mid/treble forward for some. Some will always prefer a thick, laid back sound like the LCD-4 or better yet ZMF planars. But for all you Focal Utopia, Sennheiser HD 800/HD 800 S, AKG K812, Beyerdynamic T1/T1 Gen 2, and HiFiMan HE-6 lovers, the SR-009 or SR-009S is your ultimate headphone most likely. It beats all of those in nearly every area, the exceptions being imaging versus the Sennheisers, but the SR-009 images so impressively anyway and if you really want more, I'd suggest loudspeakers. If you want neutrality and realism above all, the SR-009 or SR-009S is your ultimate headphone.
Sound Stage/Imaging
Superb width, depth, and height. Best in each category of any headphone I've owned by far. Imaging is precise and very natural, also the best of any headphone I've owned by far. Most importantly is the flawless instrument separation and sense of layering; no sound overlaps where it shouldn't, which is standard practice for elite open back headphones. But even then, the SR-009's instrument separation clearly surpasses every other headphone I've owned, which combined with the sound stage makes for very immersive listening.
The SR-009's most impressive sound stage dimension is its depth. You're going to need something like the Sennheiser HD 800 / HD 800 S, maybe the Abyss Phi/Phi CC, and of course the Stax SR-009S to compete here, and you will need something like the AKG K1000/MySphere (and maybe the Stax SR-Sigmas?) to win here.
Comparisons
When comparing the Stax SR-009 + Mjolnir Audio KGSSHV Carbon to the Audeze LCD-4 + Mjolnir Audio Pure BiPolar setup, the latter sounds veiled, unrefined, two dimensional, not detailed, with a flat sound stage and poor imprecise imaging in comparison, plus the LCD-4's horrible lower treble dips ruin vocals, pianos, and many other sounds.
But the LCD-4 does sound "thicker" in the traditional sense: there is considerably more bass presence, creating more emphasis on the lower frequencies. The LCD-4's bass is always present, when it's not called for then you can still hear/feel it waiting in the background waiting to explode, and when it explodes there's more of it. More... but of considerably lower quality than that of the SR-009.
I really was not expecting the Stax SR-009's bass to far outperform that of the Audeze LCD-4. While the LCD-4 has more quantity, it's two dimensional in comparison while the SR-009's transparency and resolution brings out tons of hidden sounds from the bass region... and every other region, and the bass texture is so much more real. The only real concrete advantages the LCD-4 has are deeper bass extension and stronger sub-bass presence which are fairly minor, then on top of that subjectively some people will prefer the added bass presence of the LCD-4.
There's no way the SR-009 should cost less than the LCD-4 if you ask me. The LCD-4 has far more treble woes than various good $500-1,000 headphones, making it sound more artificial in comparison. And it cannot compete with the SR-009 technically. If people were to blind test both of these systems, I suspect most if not all would guess that the SR-009 is the much more expensive headphone. I wish I could've blind tested them, but I returned the LCD-4 a while ago.
Compared to the LFF Code-6 + Mjolnir Audio Pure BiPolar, the Code-6/HE-6 is clearly like a much lower end version of the SR-009. The Code-6 has, in comparison, soft muddy bass, weak sound stage and imaging, thin mids, thin treble that lacks airiness, lack of detail and transparency. Definitely not the same level.
The Stax SR-009 and KGSSHV Carbon is the biggest headphone upgrade I have ever made. Going from the Audeze LCD-4 and LFF Code-6 (and I would say the Sennheiser HD 800/HD 800 S and Focal Utopia as well based on my experience with those) to the SR-009 with an elite amp is a bigger upgrade than when I went from a Cooler Master 5.1 surround headset to an Audio Technica ATH-A900X and Beyerdynamic DT 880 Pro and AKG K7XX.
I would say it's a bigger upgrade than going from the Sennheiser HD 598 to the HD 800/HD 800 S, because the Stax will reveal a greater amount of new sounds and detail than that upgrade, and it will offer a bigger leap in transparency and authentic full bodied portrayal of all instruments.
Conclusion
Not much left for me to say. The SR-009 when driven by an excellent amplifier such as the Mjolnir Audio KGSSHV Carbon completely, totally outclasses all non-electrostatic headphones in transparency, realism, and detail. It will introduce new dimensions, new sounds that were always hiding in the music, to every frequency range in nearly every song. I did not think this was possible. It seriously makes all non-electrostatic headphones sound "Low-Fi" in comparison, at least when pairing the SR-009 with a capable amplifier such as the KGSSHV Carbon. An SR-009 with a KGSS or SRM-353X, or a Chord Mojo tier DAC (regardless of amp) will NOT do this.
Some people have written that the SR-009 is too analytical, almost too technically perfect, and lacks euphoric character. For me, this is absolutely not the case. Since no headphone connects me to the music as much as the SR-009 (but I need to try the SR-009S), that makes the SR-009 by far the most euphoric headphone to me. All other headphones are too veiled and fake sounding to me, while the SR-009 with a proper amplifier connects me to the music directly with no obstacles in the way.
I broke this review down into the following sound sections above: bass, mids, treble, and sound stage/imaging, and the SR-009 clearly bests every headphone I've owned in ALL of those categories, as well as in transparency obviously and also detail retrieval. Yeah... hands down the single best in every category. I wasn't even expecting this. I was expecting the LCD-4's bass to outright beat the SR-009 but that's not even close to what really occurs. The SR-009's bass clearly wins in quality, it just has less quantity (but still a lot of quantity, more than any open back dynamic headphone I have used).
Thanks to the SR-009 + KGSSHV Carbon combo, I'm selling off most of my headphone gear and sailing off into the sunset (UPDATE years later: obviously my journey didn't really end here, but with loudspeakers). I'll remain interested in new amps designed by Kevin Gilmore (or existing designs further developed, e.g. KGSSHV Carbon Nanotube).
Any improvement beyond this will be so insignificant I think, as far as headphones go. No other flagship or former flagship headphone fully scratches my itch for better sound, but the SR-009 and KGSSHV Carbon and Chord Hugo 2 combination plus good analog interconnects does (if I substitute cheap interconnects it certainly does not. This combo is just too superior to all the flagship stuff I've owned or listened to in the past.
