STAX SR-009 Review

STAX SR-009 Electrostatic Headphone

STAX SR 009 Review


The Cutting Edge of Sound

If you are in the general consumer market, there are a lot of things you might expect to buy for $3,000-$6,000. You can get a nice used car for that price. You could fully remodel and upgrade your kitchen or add a small room to your house

… or you could buy a set of headphones.

Okay, so maybe a pair of $3,000 earphones isn’t on the typical listener’s wish list (most people don’t even realize headphones that expensive exist). But if you work in the audio and recording industry, a set of STAX SR-009 Electrostatic Earspeakers could be worth every penny.


…if you are a well-to-do consumer, spoiling yourself with a pair of electrostatic earphones could just be one of the best investments you make when it comes to audio technology.

Let’s check out this SR-009 review video by the great people over at Head-FI on the STAX SR-009 headphones:


Electrostatic Technology

How Electrostatic Technology Transforms the Listening Experience

The big buzzword with the STAX SR-009 Electrostatic Earspeakers is “electrostatic.”

Electrostatic technology is the newest thing in the audio world. This is the very leading edge of audio science, and it can change how you listen.

Let’s talk about how it works so you can understand what justifies a $3,000+ price tag for a pair of headphones.

All of us have occasionally forgotten to add a dryer sheet to our wash. You pull your clothes fresh out of the dryer, and you hear the crackle of static electricity. And of course you get static cling—your clothes all stick to each other and to you.

You don’t want static electricity in your clothes, but it turns out you do want it integrated into your headphones—in a controlled manner of course.

That is the foundational principle of electrostatic technology.

Imagine this: You have an ultra-thin diaphragm film (less than two microns in width) which weighs practically nothing. You suspend it between two perforated metal conductive plates. A charge is applied to the plates. This charge transfers to the diaphragm film without touching it, which in turn produces vibrations in the film. These vibrations become sound, which travels to your ears.

What is really mind-blowing about this technology is the fact that the film has almost no mass. Because of this and the fact that the film never makes contact with the plates, it is free to vibrate almost instantaneously. It is completely responsive to the charges.

The result?

Breathtaking clarity of sound without any delays or interference. This is the closest to pure sound you are ever going to hear through technology.

Your existing headphones work using a stiff cone, coil, and magnet. This system isn’t nearly as responsive; it is literally antiquated. It also makes your headphones really heavy and uncomfortable to wear. Both of those are major annoyances if you work in the audio industry and wear earphones all day.

Electrostatic technology is the first major update to audio technology in around two hundred years, but it is still in its infancy. So when you listen to music with STAX SR-009 earphones, you are literally getting a preview of the sound of the future.


STAX SR-009 Features and Specifications

There are a few different choices out there right now if you want to purchase electrostatic earphones. But the STAX SR-009 is right on the cutting edge. Check out these impressive features and specifications:

  • Frequency Response: 5 – 42,000Hz
  • Sound Pressure Sensitivity: 101dB / 100V r.m.s. 1 kHz
  • Electrostatic Capacitance: 110pF (including cable)
  • Bias Voltage: 580V DC
  • Impedance: 145k Ω (with cable, at 10kHz)
  • Maximum Sound Pressure: 118dB / 400Hz
  • Cable: Silver-coated 6N (99.9999%) copper, 2.5m in length
  • Weight: 1.3 pounds with cable, 1 pound without
  • Warranty: 1 year on parts and labor

Additional Details:

  • The diaphragm is made out of high polymer ultra-thin super-engineered plastics for superior tonal quality and a high dynamic range.
  • The metal plates used in the electrodes have been processed using ultra-precision etching. This works at the atomic level to produce the best resonance.
  • Aluminum is the main metal used in the production of the STAX SR-009. It is lightweight and sturdy, guaranteeing that these earphones will transmit high-quality sound while standing up to plenty of wear and tear.


The Earphones

sr009 stax earphonesBoth earphones contain the electrostatic technology that I previously described. Because there is no heavy cone, magnet, and coil as in traditional headphones, these earphones are extremely lightweight.

Adding to the comfortable design, the ear pads are made out of a combination of synthetic and real lamb leather. This keeps them extra cozy and provides you with the cushioning you need to enjoy hours of music. The head band arc is adjustable with a 10-step slider. You are not going to find comfort or durability like this anywhere else.


The Cable

stax sr 009 cable

The cable is made out of 99.9999% pure copper wire coated with a silver finish. It is a high-quality component which features the same sturdy build as the rest of the STAX SR-009. You won’t have to worry about it fraying or losing conductivity.


  • The overall sound quality is incredible all through the range from the deepest bass notes up to the highest, clearest trebles. The sounds are so realistic you can easily mistake them for being in the room with you. Sounds that blend together on other earphones can be picked out individually on these. Listen to a symphony and you’ll hear every instrument—and every violin string.
  • Sounds are reproduced accurately. All audio technology introduces some degree of distortion into sounds as they are processed. The electrostatic technology in the SR-009 earphones reproduce sounds with an astounding degree of precision—it sounds as close to the “real thing” as you are ever going to get. Basically, sound quality is so neutral that these phones do not really impart any special “characteristics.” If accuracy is what you are after, that is a good thing.
  • SR-009 adapts to different amps. Because these earphones are so neutral, you can use them with any high-quality amp you want. You will notice there are distinct changes to the sound with every amp you use; that is because the SR-009 earphones are so true to the sounds they are fed.
  • STAX SR-009 earphones are lightweight and comfortable. You can forget you are wearing them sometimes.
  • The materials and build of the STAX SR-009 are incredibly durable. Purchase these and you are making a long-term investment. They look and feel like they cost $3,000+.


  • Some STAX SR-009 reviewers have complained that the sounds of the STAX SR-009 are a little “bright.” You may discover however that this perception is simply the result of your ears adjusting to the detailed, clear sounds emerging from these electrostatic earphones. The perception may pass within a few days of listening.
  • If you are looking for noise isolation, sadly you won’t find it here. The SR-009 is pretty much useless in this respect. If you are need earphones which can block out external noise, check out some of the other recommended products on our site.
  • While the STAX SR-009 earphones work with a variety of amps, you do need specialized ones. Conventional amplifiers are not compatible with electrostatic earphones.
  • The price tag obviously is the biggest drawback. Shelling out $3,000 for a pair of earphones is no walk in the park. But if you are a professional, this equipment can take your audio work to a new level.


What’s Inside

When you purchase the STAX SR-009, you get the earphones and the cable, which may not sound like a lot, but the box itself actually is quite something. It’s a padded case made out of a special type of wood called paulownia. This wood is lightweight and cushions the earphones during shipping; it is also insect-proof and protects the phones from excessive heat and humidity. You’ll definitely want to hang onto it for long-term storage.


The Conclusion?

The STAX SR-009 Offers Unparalleled Transparency and Detail in Sound

If you are shopping in the $3,000+ price range for a pair of earphones, then you already are probably something of a sonic expert. Whether you have firsthand experience with electrostatic technology or not, you already recognize that the STAX SR-009 earphones are an evolutionary leap into the future of audio.

Again, if noise isolation is a concern, or if you dislike “bright” sounds, then you may want to consider another product (Check out our KSE 1500 Review and see if they fit what you need).

But if neither of these are an issue for you, you are going to be hard-pressed to find another pair of earphones that compete with the STAX SR-009 when it comes to transparency and detail. If you are an audio professional this is an investment in your career. Whether you are a pro or simply a dedicated music appreciator, these earphones will take your listening experience to a new echelon.


Still on the fence?

Here are a couple review excerpts which sum up the STAX SR-009 experience:

“Well, I think it is pretty much a perfect headphone. Simply amazing. I cannot find any defects in the sound, at least with good amplification. They look good and they are comfortable. You simply cannot beat electrostatic technology done well, and done well it is.” – Amazon Customer

“The 009s are truly amazing headphones. I smile every time I put them on. They are so transparent, had beautiful midrange and vocals, yet kick in the bass like the best Planars (LCD3s). Forget the Senn HD800s, or pretty much all others IMO. These will be an end game if you can afford them. They do need a good front and a decent amp. Best headphone in the world? I would say a resounding YES!” – Kaiti


Did you like this review on the STAX SR-009? Be sure to check out the rest of our site for some great overviews and in-depth research on various audio technology products.