STAX SR-L500 MK2 Electrostatic Headphone Review.

When I sat down with the SR-L500MK2 and put on a favorite piece of music from my iPhone, the presentation brought tears to my eyes. I was a bit embarrassed to be crying, but I was told that was not an uncommon experience. Friends I know who are from the music business or professional audio world have all spoken with reverential praise about their STAX headphones. When I was asked if I would like to review the STAX SR-L500MK2, I couldn’t say yes fast enough. I wondered if spending time with the same model of STAX I listened to at CanJam would still give me goosebumps and a transcendental experience of music.

When I heard the STAX SR-L500mk2s for the first time I thought “These sound like they were made by angels”. The sound is spacious and light. The detail that is revealed makes listening to old favorites, a whole new listening experience. These are headphones that honor the music. They are primarily handmade, and simply holding them reveals how different they are from any other type of headphones. They are very light, compared to the planar magnetic or dynamic driver headphones I currently have in my collection. The STAX engineers design and manufacture all the equipment that goes into the crafting of their headphones and the special energizer amps that provide the constant voltage to the diaphragms.

Electrostatic headphones have been around since STAX developed and brought to market the world’s first, called the SR-1 in 1960. The Lambda series was introduced in 1979. The current Lambda models are the SR-L300, SR-L500Mk2, and the SR-L700MK2. The SR-L300 was released in 2016 and the SR-L500MK2 and SR-L700MK2 were released in 2019. In addition to the Lambda line, with its rectangular headphones, there are more traditional-looking models. For example, Mel Martin has written about the STAX SR-009S headphones, and Carlo Lo Raso has written about the STAX SR-007A headphones.

The technology that makes an electrostatic headphone is quite unique, though somewhat similar in form to a planar magnetic headphone, since both use a super thin film suspended between plates; magnetic for planar, and electrically charged for electrostatic. The high-voltage audio signal that charges the plates is provided by proprietary energizers and thus STAX is its own ecosystem; they are not compatible with any other companies’ hardware. The almost weightless diaphragm floats between two parallel fixed electrodes. The low-mass film is supplied with the biasing voltage from the energizing units and is pushed and pulled by the opposing charges created by the electrodes when the fluctuating voltage of the audio signal is applied. The continuous flow of alternating voltage in response to the audio signals causes the film to vibrate without lag, providing undistorted sound waves.

Phew! I must admit, even though I can understand the principle of the push and pull of opposing electrical charges, it is still a mystery to me how a vibrating, lighter-than-air film can reproduce, in exquisite detail, the music I love.

The STAX company was founded in 1938 in Japan. The Kanji characters that make up the name mean quiet soul or spirit, and this has been the fundamental driving force of the company. If there is one guiding principle behind the products, according to the STAX literature, it is to “create products that bring our listeners to a moment of sublime peace.”

In Japan, there is a philosophy called shokunin which, when translated, means “mastery of one’s profession.” It’s a term that not only embodies the physical requirements of a craft, but a perspective that emphasizes the communal value of creating things that others can use … this perfectly describes what I’ve learned about the remarkable old-world craft and apprenticeship culture that imbues STAX employees. Led and taught by Kazuo Suzuki, who has had almost 50 years of service to STAX. He will turn 70 this year and is the longest-serving STAX employee to date, and affectionately and genuinely is referred to as their living legend. Suzuki-san is the only employee to have worked alongside the company’s founder, Naotake Hayashi. A small group of engineers hand-build their products after apprenticing for several years with Kazuo Suzuki.

Kazuo Suzuki, courtesy of https://staxaudio.com

I was told that the dedication to controlling every aspect of design and manufacture means that if a tool or even a special table is needed, it will be created in-house. Thus, the attention to detail and execution of production methods are tightly controlled to very high standards.

In addition to the SR-L500MK2s, I was sent two energizers: the SRM-500T, which is a vacuum tube desktop amp, and the brand new SRM-D10 2, which is a portable, DAC/amp that runs on lithium-ion batteries and has both USB-C and 3.5mm inputs. The USB interface chip is built on USB audio class 2, supporting PCM signals up to 384kHz and DSD 256 audio. The unit arrived almost fully charged and is charged by USB-C. It is by far my preferred way of listening, as I am no longer tethered to my desk.

At the time of this writing, STAX is offering a bundle special for both the SR-L500 MK2 and the SRM-500T, I believe in honor of their 85th anniversary.

When holding the SR-L500 MK2 Earspeakers for the first time, I was startled by both how light and how fragile they seemed compared to the full-size headphones I was familiar with. They are made primarily of high- quality plastic with deep, well-cushioned faux-leather pads that are very comfortable for long listening. The thin, but sturdy aluminum arms are a rigid extension from the headband and attach to the headphones. The headphones can tilt freely for a comfortable fit. The cage-like rectangular ear-cups looked like their name; speakers; albeit tiny speakers. The flexible 5-pin 2.5m ribbon cable is detachable.

The headband (ARC) assembly has a 10-click slider mechanism for head pad height adjustment. Once set in place, it holds that setting firmly. For larger head sizes, I’m sure the fit is nicely aligned with the ears, and the clamping force is gentle, yet snug enough for good contact and hours of comfortable listening. However, as a woman with a smaller head, I could not get the headphones short enough to match my ears; they needed an “11” or even a “12” notch to place them optimally for me. I solved the issue by wrapping layers of fabric around the headband until I got a good fit. A goofy look for sure, but it worked.

They are open-back, and, like all open-back headphones, offer no isolation to either the listener or anyone who happens to be nearby. I love open-back designs and I find the SR-L500MK2s wonderfully open and airy. No problem with ears overheating when wearing these! The synthetic leather pads are large and soft with just the right amount of firmness. As I studied the way these are put together, the word “suchness” came to mind. Every detail has been considered and chosen with care, and, knowing the philosophy of the STAX company, it seems the design of every part and function is attended to.

The cable is a flexible ribbon of HIFC parallel 6-strand, low-capacity, special wide copper cable, 2.5m full length. I love it. It bends, it folds, it is supple and easy to move around. It is also long enough to allow sitting away from the energizers. This was especially nice with the portable SRM-D10 11 DAC/amp, as I could take the headphones out to the living room and sit back in the stressless chair by the fire and really bliss out.

As light and delicate as the headphones seemed, I was intimidated by the heft and size of the SRM-500T energizer. The complexity of the inputs and outputs was daunting, as it needs a separate DAC (not included) to feed the audio from the source, through the amp, and to the headphones. I’m sure this is a common practice for more advanced enthusiasts, but six months ago I thought I was cool because I had a Dragonfly DAC/amp plugged into my iPhone. I had never had this kind of equipment to hook up.

I had a moment of panic as it turned out that an RCA cable is needed to feed the audio from the DAC to the SRM-500T, and I wasn’t sure I had any. However, a box of cables that I meant to organize someday, came through for me. RCA cables are not included, so be forewarned. My Topping DX7Pro DAC/amp turned out to be straightforward to connect, and my MacBook Pro provided the audio to the Topping. The headphones plug into the 5-pin input on the front. I felt a little superstitious about turning on the energizer, all that voltage! I think I was afraid of blowing it up if I got something wrong. Upon powering up, the power light blinked for a few seconds while the tubes warmed up, and then glowed steadily. Everything worked, the music flowed, and my adventure with STAX Earspeakers began.

The manual for setting up the energizer is minimal at best. In fact, if I could offer one suggestion to the graphic designers at STAX it would be to include a detailed and easy-to-read set of instructions or a link to those instructions on their website.

A beautiful touch I noticed on the metal case of the energizer is the pattern of the cooling vents around and above the vacuum tubes. The metal above the tubes is raised in circles that I assume match the form of the tubes underneath, with radiating vent holes that reminded me of flower petals or a radiating star. The entire vent pattern is worthy of a wood block print. Again, I see the art of craftsmanship in how everything is built.

The front of the SRM-500T is brushed aluminum and the volume level dial is large and has an option of controlling left and right channels separately. The beveled edge of the dial is another beautiful and subtle touch.

I found finding the best balance of volume between the STAX energizer and the Topping DX7Pro a bit of trial and error. Once I found the best settings between the two, setting the dial between 6 and 8 gave plenty of volume.

While I was reviewing the SRM-500T, STAX released a brand-new version of their portable lithium-ion DAC/amp, the SRM-D10 11, and sent me one of the first units to review. The packaging was sturdy and elegant, and simple graphics were printed on each of the boxes for the cables, various international plug adaptors, and the charger. The accordion-fold manual was clear and detailed.

This beautifully machined DAC/amp looks like it could have been made in the 1930s during the romantic era of machines; a time when how something looked was as important as how it was used. It is fitting for a company founded in 1938. The controls are simple, and the large, knurled knob has both left and right channels and rotates with just the right amount of pressure.

On the back, the inputs and charging port are clearly marked. The DC/charging port is USB-C, and the 3.5mm line-in and USB-C connection are chosen by a selector switch, which was set for USB-C out of the box.

The SRM-D10 11 is compact and quite portable. It is solid and heavy for its size. It must be magic that the engineers at STAX use to pack a small device with a battery, a high-quality DAC, and electronics that can produce enough voltage to drive any of the Pro versions of the STAX line of Earspeakers. The volume is full and loud at the 10 o’clock position on the dial. Turning the volume halfway was almost too loud. The quality of the audio produced by the DAC on this portable is detailed, warm, and lush. The soundstage and placement of instruments are wide and precise. If I was blindfolded and listened to this, I wouldn’t be able to tell you which unit it was. The run-time between charges is around 4.5 hours, I’ve been told, and you cannot use it while charging.

My primary listening headphones are open-back planar magnetic. I love the detail, transparent and open spaciousness, and a soundstage that is wide and deep. I’ve always thought of their sound as light and airy compared to closed-back dynamic driver headphones. However, after spending about an hour listening to the STAX, and then putting on the planar magnetics, I was shocked; in comparison, they sounded dense and thicker; it was like honey compared to champagne. I love both, so it wasn’t a negative, but it was startling. The level of micro-detail was mesmerizing, and the way the sound floated effortlessly reminded me of how the atmosphere is at 10,000 ft.; so clear and delicate. Everything plays effortlessly; turning up the volume doesn’t produce any distortion. The bass was punchier and more present than I thought it would be, given the reputation of both electrostatic speakers and headphones not being able to reach deep. Perfect for jazz and vocals and if there was anything in the bass that I was missing, it would be the deep percussive punch I enjoy with some dynamic-driver headphones, but that is really a minor quibble because what they lack in big, punchy bass they make up for in detail, lack of distortion, and the sensation of feeling how the atmosphere holds and responds to that bass in a live performance. I think I’m getting a little “out there” in trying to be accurate, but there it is.

Unless otherwise noted, Qobuz was the music source.

On this album, he performs with Claire Antonini, who plays the theorbo, a lute that comes from Renaissance Italy. The lute has six to eight strings that are played, while six others resonate harmoniously through vibration alone. This is a perfect performance to capture the magic of electrostatic headphones. Two stringed instruments, nothing more, where the space around the musicians and between the notes, and the resonances of the wood and strings are presented in breath-taking clarity, detail, and depth, and where both the deep bass notes and the delicate highs are given equal weight. I have not come across any type of headphones that matches the grace with which this style of music is played by an electrostatic Earspeaker.

“Diamonds on the Soles of Her Shoes” captures the depth and breadth of how the SR-500LMK2s can also rock with the best of them. The a cappella male voices open center, left, and right, highlighting the precision of vocal placement and the three-dimensional soundstage these headphones produce effortlessly. When Paul Simon joins in, positioned in the center, I can hear singers precisely placed to either side of him. The guitars and drums explode into the mix, bringing layers of horns, crisp drumming, and more voices. Paul Simon’s lead vocals never get compressed by the layers of sound, and the placement of the musicians is never lost. The dynamics go from the deep bass of the drums and male voices all the way to the sparkling high notes of the guitars, and the STAX never lags, and, where some headphones might have a challenge in the rhythm changes and rapid pace, the STAX were simply invisible, letting the music shine as if it was a live performance.

This album was recorded for headphones, and what a three-dimensional, binaural treat it is. The ethnomusicological field recordings, layered with natural sounds of water and insects, plus the eerie layering of electronic sounds took me on a journey that was mind-altering (in a good way). The SR-L500MK2s held their own effortlessly, which was a delight since there were so many layers of sound. Each track flows into the next, bringing deep drumming at times, delicate bird song, or the snap of burning wood, and the STAX, again, performed flawlessly. The final piece ends with no music, just layers of natural sound, and, finally, the sound of footsteps crunching from left to right and out of the frame, as if guiding us out of that world and back into our own.

With any electrostatic headphones, if you don’t already own the proprietary energizer needed to play them, the investment is considerable. So, these are not a casual purchase. However, anyone who has a love of music, and already knows the joys of sitting down and giving undivided attention to what is playing, may well find the years of enjoyment in owning these a great return on the investment. And the cost of the SR-L500MK2 paired with the portable SRM-D10 11 is right in line with many popular headphones on the market.

Now that I have had the luxury of undistracted time with the same pair of STAX headphones I heard at CanJam, I can confirm that the first emotional listen was not just being caught up in the moment. The SR-L500 MK2 are so good, that I’m wondering what the more expensive models could possibly be offering. I say that with respect, because from what I’ve learned about STAX as a company, they don’t make anything casually just to have another model. In fact, with other brands and types of headphones, I’m always curious about the next level up, or what is coming soon. With the SR-L500MK2s I don’t feel that. Other than the fact that they are just too big and clunky for me without modification, they seem close to perfect. And now that I got to enjoy them with the new portable SRM-D10 11, and no longer being tethered to my desk, I almost think they would put my beloved planar magnetic headphones in second place for much of what I listen to.