Stax SR-L700 earspeakers headphones REVIEW

Product Name: Stax SR-L700
Product Type: headphones
Price: $2499.00
Reviewed By: Jez Ford
Magazine: Sound+Image
Distributor: Audio Marketing
Who Sells What/Website: Stax
Every hi-fi category has its legendary products, and for headphones few would deny a place in that pantheon to the Stax Lambda Signature ‘earspeakers’ (as Stax still calls its headphones). The Japanese company had, after all, developed the world’s first electrostatic headphones at the dawn of the 1960s; the original Lambda came 20 years later, and the Signature in 1987 — it became a reference product for a decade. This reviewer remembers being once saddled with a test of 70 types of blank tape cassettes for a UK hi-fi title; this potential nightmare of comparative star ratings could be reliably completed only once we had in place the spectacular audio resolution of a pair of Lambda Signatures, with their dedicated valve amplifier attached to another legend, the Nakamichi Dragon cassette deck.  
Stax today is not quite the same company that released the Lambdas — it was revived from insolvency in the 1990s, and more recently came under the ownership of Beijing-based Edifier. Its top earspeakers now sport circular headshells, an outrageous departure from the company’s trademark rectangular designs. So we were delighted to be offered a review loan of the new yet more traditionally hung SR-L700s, along with one of the company’s dedicated driver units, the SRM727II (pictured below). Further delight to find that the ‘L’ in the name stands not only for Lambda, but for “advanced-Lambda”! And most delight of all when we burned them in and then put them on.   
In brief, then, the luscious tech of this open-backed electrostatic design includes thin-film diaphragms (hand-selected, we gather) sitting between the fixed electrodes that are machined through three-layer heat-diffusion etching, driven and provided with the required 580V of bias voltage through their low-capacitance high-purity cables from the driver unit, a fine piece of electronics, and very Japanese in its impeccable build.
The SRM-727II is just one of Stax’s options for driving the SR-L700s, introduced in 2007 and employing a semiconductor output drive stage and non-feedback output stage for the first time in a Stax driver unit. We can’t judge it against the similarly-priced valve driver, or the less expensive options, but we can tell you that the sound which emerged from the lambs-leather earcups was simply divine. Nothing creates a sense of soundstage space and detail like electrostatics, but the Stax deliver solid bass as well, and such tight fast response that unexpected transients had us physically jumping — one such was the start of Led Zeppelin’s rough mix (rough playing, but superior production) of ‘Since I’ve Been Loving You’, where Bonham’s snare quite knocked us back in our seat (we were listening loud enough to enjoy his sqeaky bass pedal — the distortion here remains so low, that’s what you do). Everything sounded wonderful (“EVERYTHING” screams our listening notes), and after one long evening under their spell we went off to hear Sennheiser’s Orpheus (audition report in the Feb-March 2016 issue of Sound+Image) thinking they would have quite a job to sound better. They were softer-sounding while still achieving the same revelations, but really, you can’t buy the Orpheus, and you can certainly buy the Stax. Their open leakage makes them useless in a shared room, of course, unless you plug a second pair into the driver, but that aside, if you’re after a top-level headphone (or earspeakers, sorry), then you simply can’t NOT audition Stax electrostatics. We’d recommend taking a nice long playlist with you. Maybe stay the night. 
Stax SR-L700 earspeakers $2499 
tested with SRM-727 II driver $3399 
Type: push-pull open-back electrostatic  
Driver size: 90 x 50mm
Impedance: 145kΩ (including cable, at 10kHz)
Weight: 360g 
Warranty: One year
Product page: Audio Marketing