STAX SR-007S Earspeaker System Review

Let’s see how the STAX SR-007S carries on the traditions of the original STAX SR-007 electrostatic earspeaker, STAX’s name for their headphones.

The STAX SR-007S are beautiful. Right out of the box I was struck by how simple and elegant they are. There is nothing ornate or ostentatious about the solid and functional design. The earcups are made of a single piece of stainless steel, which STAX refers to as the Anti-Resonance Structure (ARS). The new sheepskin earpads are a deep brown color. The metal headband support reminds me of Art Deco metal sculpture and has, to me, the quality of what the Japanese call Shibui. Shibui refers to subtle, understated, and unassuming beauty that may not be immediately apparent but reveals deeper complexity and refinement upon closer inspection. The brown headband is stamped with SR-007S and is a thick, rubberized material. The newly designed outer cup has a high-precision etched grill that has 20% fewer air vent holes, which STAX claims optimizes the acoustic sound profile. There is a detachable cable structure at the bottom of the cup, which is designed for easy maintenance, and longevity by having replaceable cables.

Those of us who love headphones chase the elusive promise of perfect sound. But what is perfect sound, and for whom? Hip Hop? Live jazz recordings? Classical or acoustic? Dynamic driver headphones can offer thumping bass for Hip Hop and provide the all-around good sound I first learned about in my early headphone years. And then, I discovered planar magnetic, and the bar was raised, and I found a new joy in listening to live jazz and acoustic music, and I was adding sound stage and detail to the mix. Then there is electrostatic. I heard my first electrostatic headphone at CanJam SoCal 2023. It was a moment etched in my memory. A moment when the music I was listening to was elevated into a realm so sublime it brought tears to my eyes. Those headphones were from STAX. Not only was I hearing detail and accuracy, but a lifting of a veil as if the spirit of the music was being released. I’ve been a bit obsessed with that sound ever since.

The history of STAX is an interesting one, and instead of repeating myself here, I wrote about the history of the STAX company in my review of the STAX SR-L500 MKII. I also reviewed the STAX SR-X1000 system, an “affordable” electrostatic, which took me further into the STAX ecosystem, and an experience of a slightly different sound signature. The journey continues with spending time with the SR-007S and the SRM-700S solid state energizer that STAX included to run them.

The SR-007S arrived in a plastic suitcase-style carrying case. It was well protected with heavy foam padding. Both it and the tightly coiled cable were packed together. The power cord and the RCA cable for connecting to a DAC were packed separately. The case is fairly large and designed as a sturdy storage case, more than a travel case.

The SR-007S are light but reassuringly sturdy and well-constructed. The matte sheen of the stainless-steel ear cup set against the simple metal screen and the dark brown leather ear pads is quietly handsome. The metal headband is minimalist and beautifully designed. The earcups are generous and deep. The detachable 2.5m flat ribbon cable is standard issue. It has updated diaphragms and fixed electrodes and a newly designed large, circular earcup housing which STAX says uses a new ARS (Anti-Resonance Structure) for enhanced rigidity and vibration reduction.

The SRM-700S electrostatic driver unit has a utilitarian dark-grey coated steel body with a brushed aluminum faceplate. The quality and precision of the faceplate are beautiful. The front is simple; no screen, just the power button, two 5-pin Pro-Type earspeaker jacks, a large volume dial with dual-gang controls for right and left channel balance, two source lights for RCA and XLR and a level control light for either external/bypass or internal. The volume dial has a beveled front edge and has a silky-smooth and precise rotation. Both channels rotate together unless they are moved separately. The lettering is tiny. Regarding the Pro-Type jacks, they are designed for the “Pro” STAX headphones, which require a higher bias voltage than the earlier model headphones, so they are missing the 6^th center-pin, making it impossible to accidently plug in older pre-1992 headphones.

The rear panel has XLR inputs, gold-plated unbalanced inputs, and gold-plated outputs. There is a source dial to switch between XLR and RCA and level control mode dial for internal or external (bypass) volume control, and a standard 3-prong 50/60Hz power supply.

The SRM-700S has a sibling, the SRM-700T, which is the vacuum tube version. The SRM-700S is solid-state and utilizes custom-made low-noise dual FET (Field-Effect Transistors) at the first stage and J-FET (Junction Field Effect Transistor) at the second stage. According to STAX, those who prefer warmth and richness would choose the SRM-700T, while those who prefer a precise, detailed, and more accurate sound might choose the solid-state version.

The SRM-700S energizer/driver unit requires a separate DAC, so I connected it with the supplied RCA cables to the Rotel DX-3 DAC/Amp which has an excellent DAC. The brushed aluminum DX-3 looks like it was made to sit next to the STAX energizer. The DX-3 is connected to my MacBook Pro by USB-C to USB-B as the music source. Both units are powered by the Claris Sextet power conditioner. After setting the DX-3 mode to DAC- only, they were working flawlessly together.

Putting on the headphones for the first time, I was a bit disappointed to see that, like all STAX headphones I have listened to, they couldn’t adjust short enough for my smaller head. I wrapped some material around the headband, and the fit was perfect. Honestly, that is my only quibble with the design.

Listening to music was sublime. I was curious to see how the SR-007S would be different than the other two models I had spent time with, the SRS-X1000 and the SR-L500. The effortless, spacious clarity that is the electrostatic sound was the same. However, there was more warmth, and the bass had fullness and punch. I recall someone telling me that they felt the SR-007 series was for folks who want warmth and depth, and these certainly have those qualities, while maintaining everything that I love about the electrostatic sound. I mentioned effortless; these feel almost lighter-than-air in the way music seems to shimmer and float. The separation of instruments and voices is crisp, and the tiniest details are clear. Listening to the classic “Take Five” by Dave Brubeck, the sharp crack of drumsticks on the edge of the snare drums, and the snare drums themselves were presented with the microscopic detail I expected. The surprise came during the drum solo; all the drums had force and resonance, and the timbre was spot on. I felt like I was in the studio with the band. The width of the soundstage was good; not the widest, but natural and appropriate for the music. As an aside, sometimes I think we give too much attention to soundstage presentation. The three-dimensional space is important for realism and count me as a fan, but there are so many other qualities that share the spotlight.

The SR-007S have an addictive sound, and I lost count of how many different genres of music I played. I found that the source music mattered. These headphones are so transparent that at times that if a recording had poorly recorded highs, I could hear it. I’ve had the same experience with other flagship headphones, so I place the fault with the music, not the headphones.

“Claire de Lune” is so much a part of the fabric of classical music, that it is easy to overlook. However, the exquisite solo performance by Nikolai Lugansky is breathtaking. “Moon Light” shimmers and floats like moonbeams on a clear night. If there was a single piece of music to reflect what electrostatic headphones do so well, including the SR-007S, it is this piece of music played on a grand piano with spare, pure notes reverberating on and on with Nikolai’s light touch on the keys.

The name of the album says it all; Brian Wilson suffered deep depression and withdrawal from the public stage. On Caroline No, his voice is raw, and 30 years older, and he doesn’t soar into the highs like he did when he first recorded “Caroline No” in 1966 in collaboration with Tony Asher for the album “Pet Sounds”. It is heartbreakingly beautiful and deeply expressive of how vulnerable Brian Wilson was. This version is jazz-like; Brian’s piano playing is delicate. The SR700S capture the opening tambourine and guitar with bright clarity. The timbre of each instrument is accurate and brings a lively you-are-there feel to the music. I was reminded of just how brilliant Brian Wilson’s song writing was. When I hear a song I grew up with, it is easy to gloss over actually hearing it; been there, done that… but this version was a jolt of espresso to my brain. I heard it as if for the first time, and I could hear why the music duo “Carolin No” were inspired to name their band after it. Not to sound like a “broken record”, but this is another performance that highlights what makes STAX headphones a music lover’s headphone.

With the SR-007S STAX has created a gorgeous sounding set of electrostatic earspeakers that builds upon the appeal of the original SR-007 and takes it to the next level. Electrostatic detail, a sense of warmth, and impactful bass. Outstanding!

The engineers at STAX have created, in my opinion, a very special headphone. Inspired and taught by the legendary engineer Kazuo Suzuki, who has been with STAX for over 50 years, the current generation of engineers continue to refine and honor the tradition of excellence. This third model of the SR-007 series, the SR-007S are a result of the continuing research and push towards perfection that STAX is famous for.