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WooAudio WES Electrostatic Headphone Amplifier and Stax SR-007 Mk2 Electrostatic Headphone Review

July 13, 2009 By Steve Guttenberg

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WooAudio WES and Stax SR-007 Mk2
Stax SR-007 Mk2
WooAudio WES

All ears!

Lucky me, I recently reviewed three of the world's very best headphones, the Audio Technica ATH-W5000, Denon AH-D7000 and Sennheiser HD 800 for Home Entertainment, due in the September issue.

But the advancement of high-end headphones doesn't stand still and now I've heard something even better: The WooAudio WES headphone amplifier and Stax SR-007 Mk2 headphone.

WooAudio WES and Stax SR-007 Mk2

The sound of nothing

Every high-end audio designer strives to make gear that doesn't have a sound per se so the music magically appears, fully formed and real.

But back here on planet earth every CD player, turntable, amplifier, speaker, and headphone I've heard has a sonic signature. They inevitably color the sound, shrink its natural dynamic range, add distortion, and fail to reproduce the full dimensionality of the music.

They can still sound awfully good, but fall far short of producing the illusion of live music.

Headphones never sound believably real, but they have major advantages over speakers, even cost-no-object high-enders priced within spitting distance of a Porsche 911 GT3 or Maserati Quattroporte S.

Ultra-high-end speakers still have to submit to the vagaries of room acoustics anomalies--room reflections, reverberation, standing waves, and ambient noise--that take their toll in a multitude of ways.

Headphones leapfrog all of that, there's nothing between the headphone and your ears. And headphones, even edge of the art ones live in a more attainable section of the high-end universe. The cost of true greatness ain't cheap, but it's a tiny fraction of the MSRP of the very best speaker based systems.

Which brings us to the WooAudio WES Electrostatic Headphone Amplifier and Stax SR-007 Mk2 electrostatic headphone.

Stax SR-007 Mk2

Stax headphones use a very different operating principle than dynamic headphones (pretty much every headphone from lowly ear buds to the very best full size headphone are dynamic designs).

Stax are different, they have been making electrostatic headphones since 1960 in Japan, and their current flagship model, the SR-007 Mk2 is what I'm using with the Woo WES headphone amplifier. The Stax SR-007 Mk2 isn't new, it premiered in 2007, but the WES is.

Stax electrostatic headphone prices start at $380 for the SR-202 'phones (Woo also offers the GES tube amp for Stax headphones that runs $1,450). The WES is a completely different design and will also work with Sennheiser Orpheus electrostatic headphones.

Electrostatic headphones (or loudspeakers) have lower mass diaphragms compared with dynamic drivers' heavier cones and domes of "regular" speakers.  Domes and cones are propelled by a moving coil from either the center or edge of their diaphragms.

Stax SR-007 Mk2Electrostatic drivers generate force and pressure evenly over the diaphragm so it's not as prone to resonances and breakup distortion as dynamic drivers. For a full detail, check out Wiki's article.

English translation: Electrostatic speakers and headphones can produce vastly lower levels of distortion. That low distortion is heard as greater clarity.

The catch? Pure electrostatic speakers have significant bass and dynamic range limitations, but that's less of a concern with electrostatic headphones.

Also, they don't work with standard headphone jacks, you need to use specially designed electronics with these 'phones.

The Woo WES is such an amplifier. It is an all-triode tube drive, fully-balanced design, the prototype unit I'm reviewing has a total of ten tubes (four EL34 power tubes, four 6SL7 driver tubes, and two 5AR4 rectifier tubes),

Production models will have eleven tubes. The machined, all-metal dual chassis are beautifully crafted, the rear panel houses four line-level inputs (two XLR. two RCA).

A look inside reveals no circuit boards, all wiring is "point-to-point." That's a very expensive way to manufacture amplifiers, but WooAudio believes point to point wiring makes for better sounding amps.

The amp also features hand-made inductors and even the machined cone feet are designed specifically for the WES.

The WES, like all Woo amps, was designed by Wei Wu, and they're hand crafted in WooAudio's factory New York City.

Each WES, slated for release in October 2009, will be built to order over a four-day period. There's a pre-introduction price of $4,500, full retail is expected to be $4,990). All WooAudio electronics are sold direct from the factory, the waiting list is typically three to four weeks.

WooAudio WES

Back to the sound. With acoustic jazz the clarity is superlative, never overdone, which is the way live, unamplified music sounds in a good concert hall or club. The Woo/Stax combo is the closest thing to being there I've heard to date.

Sticky Fingers, one of the Rolling Stones best albums, and one I've heard hundreds of times, revealed new details. Keith Richards' guitar wizardry lights up "Sway" like never before, and I'm hearing a sense of depth and space around Charlie Watts' drum kit for the first time. I feel like I'm hearing a band live in the studio, not a recording. Quiet details, such as subtle reverberation in the mix are newly audible. This is something you need to hear to believe!

Amy Winehouse's Back to Black uncorked heretofore unheard details of the brash electric guitars contrasting against lush orchestral strings. And Amy cooing in my ears like never before tops off the experience.

WooAudio WES - Amp PortionI wish I had the best headphone I'd heard up to this point, Senneiser's HD 800, to compare with the WooAudio WES/Stax SR-007 Mk2, but as memory serves it wouldn't be close. The HD 800 is superlative in its own right.

It's just the Woo/Stax combo trumps it on every count, except one: The HD 800's out-of-the-head imaging was more speaker-like, the Stax isn't as wide-open, but it's more dimensionally developed.  

Listening to my Grado RS-1 and Sennheiser HD-580 headphones plugged into a WooAudio WA 6 SE headphone amplifier, the sound was more "contained," flatter, more two-dimensional than the Woo/Stax combo. Those two dynamic headphones are, on their own still excellent, but they now sound veiled by comparison to the WooAudio WES/Stax SR-007 Mk2. The magnitude of difference is HUGE, and that's rare in the audio reviewing game. I'm still trying to take it all in.

A friend with a $200,000 high-end audio system was knocked out by the Woo/Stax sound. Five seconds after donning the headphones his eyes lit up and he said "Wow!" He listened intently for ten minutes and said the system's resolution of fine detail was more or less on par with his own system!

Yes, the WES' 12 by 17 inch footprint is bigger than most headphone amps, and the tubes put out a lot of heat, but it's so good! If you're a headphone lover you have got hear what the Woo/Stax combo can do. It's not perfect, but it's closer than anything else.

Bottom line: The WooAudio WES and Stax SR-007 Mk2 headphones will dazzle your ears with state of the art sound for a tiny fraction of the cost of a system built around speakers.

WooAudio WES Electrostatic Headphone Amplifier: $4,990 
Stax SR-007 Mk2 Electrostatic Headphone: $2,410

CONTACT: wooaudio.com

For more headphone and headphone amps reviews, check out:
Improve Your Hearing and High End Headphone and Headphone Amp Roundup


Nice review. Stax sell the Omega 2 with their own amps, but those amps are built down to a price and bottleneck the potential of these headphones. But the Woo amp is a solid design that cuts no corners and sounds great, and lets these headphones shine. There are other good amps for the Omega 2 too - specifically the Headamp Blue Hawaii, which costs about the same.

I'm using the older (and IMO slightly better) version of the Omega 2 with an aftermarket amp and it sounds bloody fantastic. Incredibly clear and yet so wonderfully musical and lush. The only system I have heard that was better was at a well-known mastering lab in California, and the difference here was mainly the fundamental difference in presentation with headphones vs. speakers, and a high-rez master as source material. The voicing and tonality of the two rigs was pretty much the same.

Thanks for a great review.

cool blog

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