Stax SR-009S Electrostatic Earspeaker Review

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The Stax brand has been synonymous with electrostatic headphones – aka earspeakers – since the early 1960s. Back then, they didn’t have much competition. Later, Shure and Koss produced electrostatic models but they were aimed at a more entry-level than most of Stax’s offerings, which were more about studio or audiophile use. In the past couple of years, more manufacturers have entered the arena with electrostatic headphone designs, which has prompted Stax to up its game. The company’s current second to their top-of-the-line SR-X900 is the SR-009S, the subject of this review. I reviewed the L-300 for a couple of months ago. You can buy approximately 10 L-300 headspeakers for the price of one pair of SR-009S. What do you get for that increased price? Let’s find out.

STAX SR-009 electrostatic headphones reviewed
The STAX SR-009 are next-level comfortable on your head

What Makes the Stax SR-009S Electrostatic Earspeakers Special?

  • Changes to the Stax SR-009S stator or electrodes over the SR-009 multilayer fixed electrode (MLER) design improved air resistance and sound permeability due to better finishing and etching techniques on the MLER2. 
  • Gold plating the electrodes on the Stax SR-009S reduced electrode impedance. This also reduced the physical resonance of the electrodes.
  • The SR-009S diaphragm is made of ultra-thin “super engineering” plastic. It has also undergone some improvements over the original SR-009 design.
  • The SR-009S employs machined aluminum parts for its enclosure and yoke, yet it is much lighter than many all-aluminum headphones, such as the T+A Solitaire, and much stronger than the plastic used in the L-series. 
  • The SR-009S can be used with a wide variety of electrostatic headphone amplifiers. Stax has seven compatible amplifiers from the $995 SRM-D10 to the $6,090 SRM-T8000. Several other manufacturers make headphone amplifiers for Stax headsets, including Blue Hawaii and HiFiMan. 
  • As you would expect from a product at this price, the SR-009S uses premium materials throughout. The earpads are covered with real lambskin leather and the cable uses high-purity copper.
STAX SR-009 electrostatic headphones reviewed by Steven Stone
STAX SR-009 electrostatic, audiophile headphones on their side

Why Should You Care About the Stax SR-009S Audiophile Earspeaker?

Up to about nine months ago, the SR-009S was Stax’s top-of-the-line headset. Unlike the L series, which harken back to the early 1970s in terms of materials and basic design, the SR-009S incorporates all of the improvements in materials and design to make it into a state-of-the-art component. Also, unlike the company’s previous offerings, the SR-009S ranks as a far more rugged design. While I don’t recommend throwing or dropping headphones on purpose, it happens, and the SR-0009S will survive these kinds of real-world mishaps far better than its predecessors. 

For someone looking for the ultimate in an audiophile headphone experience, the SR-009S is right in the conversation. The earspeakers deliver on exotic design, a super-cool technology, and a way to get to audio nirvana without pissing people off with a lot of noise. 

Some Things You Might Not Like About the SR-009S 

  • Although the SR-009S uses a premium cable, it is not replaceable or removable. If your cable is damaged you will need to have Stax replace it. 
  • Since the SR-009S’ cable is not removable, if it is too short for your needs you will have to buy an extension cable. A Stax SRE-725H extension cable will run you close to an additional $150.
  • The SR-009S is and open-capsule design. If you require a headphone that attenuates outside noise and prevents others in the room with you from hearing your music entirely, the Stax SR-009S will not deliver much, if any, attenuation. 
  • Although Stax makes a portable headphone amplifier for the SR-009S, it is not really a portable headphone system. Between its open-capsule design and the need for a special headphone amplifier, the vast majority of users will have their Stax systems anchored to a desk or console. 

Listening to the Stax SR-009S Audiophile Headphones…

Electrostatic headphone designs, due to their physical properties, invariably sound fast, clean, and extremely detailed. Where Stax electrostatic designs have struggled in the past is in their ability to handle bass. The current-generation L-300 has more bass than my older SR-407, but it was less defined than the rest of the L-300’s frequency range. In comparison, the SR-009S delivers far more cohesive and impactful bass than any Stax headphones I’ve used. While not quite as impactful as the bass rendition on the Focal Utopia 2022 I reviewed recently, still I found the SR-009S delivered balanced and nuanced bass that was clearly superior to earlier Stax designs. 

On the BTS cut “Butter”, the Stax SR-009S does a superb job of keeping the low bass under control while still delivering enough punch and impact, also maintaining superb clarity and resolution in the midrange and higher frequencies. Additionally, the SR-009S delineates the different depth layers with precision.

Intimacy and inner detail are the SR-009S’ forte. Between its extremely low noise when coupled with a SRM-T8000 amplifier, its high sensitivity, and its hyper-responsive diaphragm, low-level information is presented in the most lucid manner currently available in a personal transducer. If getting closer to the music is your primary sonic goal, then I seriously doubt you will find a better high-value option than the SR-009S. 

On Billie Eillish’s “Everything I Ever Wanted”, all the subtleties of the synth keyboard’s reverb tail and multiple parts are easy to hear through the SR-009S. Also, this cut demonstrates the dimensional specificity of the SR-009S as well as its ability to retain the subtlest sighs and exhalations. 

Does the Stax SR-009S Headphones Have Any Resale Value?

Yes. I see 30-year-old Stax products for sale on a regular basis on most of the used hi-fi sites I frequent. I’ve also seen a few demo or used SR-009S units for sale. Most are priced about $1,000 less than a brand-new example. If you must sell your SR-009S, you’ll find it will go for a higher percentage of the original retail price than an under-$500 headphone, but in terms of actual dollars, you will still take a four-figure hit.

STAX SR-009 electrostatic headphones reviewed by Steven Stone
A view of the internal driver of a STAX SR-009

Who Is the Competition for the Stax SR-009S?

The Warwick Sonoma electrostatic headphone system was the first serious competition that challenged Stax’s electrostatic hegemony. Now on its second version, the Bravura ($5,995), the Warwick system also requires its own, dedicated, non-interchangeable amplifier. The Bravura also includes a DAC and accepts a USB signal, so you don’t need an additional digital-to-analog convertor to listen to digital files through the Warwick Acoustics Bravura system. 

The HiFiMan Jade II electrostatic system ($1,700) is, as you might surmise from its title, the second electrostatic headphone system developed by HiFiMan. It claims 7 Hz to 90 kHz frequency response and, as a package deal, it’s far more affordable than buying the amp and headset separately (Headphones $1,399; amp $1,599).

The Dan Clark Audio Voce ($3,299) has a removable cable and an 88mm diameter drivers that the company claims allow the Voce to get down to 10 Hz. Like all electrostatics, the Voce requires a dedicated powered headphone amplifier, but it can be used with any amplifier that supports the Stax pro specification.

STAX SR-009 electrostatic headphones reviewed by Steven Stone
STAX SR-009 headphones as part of Steven Stone’s reference headphone collection

Final Thoughts on the Stax SR-009S Electrostatic Earspeakers

When evaluating an audio component that is at the high end of the price range for its category, the primary question in most people’s minds will be, “Does this represent a good value?” While its relatively easy to see the added value in terms of better specifications, the quality of materials, and the fit and finish, it is not as easy to determine if the additional sound quality alone warrants the bump up in price. 

The Stax SR-009S delivers high performance, but, obviously, at a commensurate price. The major portion of this particular sound-quality equation is personal – do you hear a difference? How much of a difference do you hear? And finally: is it worth it to you? Finding your own answer to these questions is what our hobby is all about. I think the Stax SR-009S is stellar, but I can’t ignore the costs either. If you can, this might just be your audiophile headphone solution.

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DWR Ball

Interesting headphones to say the least.

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