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Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser

Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser

While it’s not good to start a piece of writing in the middle and sum up a whole review in a single word in the opening paragraph, the Stax SR-L700 Lambda earspeakers coupled with the SRM-006tS Kimik 2 energiser are neatly encapsulated in the word ‘graceful’. Everything about them, from the boxes they come in to the sound they make is graceful. That word has lost some of its glow in our hard-edged times, but the Stax challenges that. With good grace.

Perhaps the ultimate expression of the almost 40 year old SR-Lambda design, the rectangular SR-L700 contains a highly revised diaphragm, which in fact carries a number of ideas and parts over from the SR-009, to the point where the diaphragm could be considered a ‘SR-009 junior’, making it the best Lambda diaphragm ever made. According to Stax, this diaphragm features “a specially selected thin-film diaphragm as well as fixed electrodes, machined through three-layer stainless etching using heat diffusion.” 

, Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser

The fit has changed too. Its arc assembly is equipped with a 10-click slider mechanism for head-pad height adjustment. Once adjusted, the slider always maintains its optimal position, making readjustment unnecessary. 

The other major difference from previous Lambda models is a new cup design. It may look identical, but the structure is much lighter, and its bars are much thinner, in an effort to create ‘less cup’! Stax also reversed that cup, so now the wider part is at the back and not the front. The diaphragms are mounted at a slight angle towards to ear. In the past the wider part of the cup was always in front of the ear.

This feels a little odd to those used to Lambda designs, as if you have got the earspeakers on back-to-front. However, that feeling goes away in a few seconds and is perfectly comfortable in use. British users will find themselves saying ‘bollocks!’ a lot as they instinctually put them on the wrong way round for the first few times – other swearwords are also available.

Other elements comparatively new to Stax have been seen before in other Lambda models, such as the change in structure to the sheepskin leather ear pads (to make them more comfortable for longer listening sessions), and the 6N high-purity annealed copper wires for the core and six silver plated wires for the external cable. All of this helps to build on a design first minted in 1979 and that shows no signs of running out of steam.


Many of the Stax energisers would be good partners with the L700, but such is its quality that it deserves a quality energiser to drive it. And in that respect, we welcome back an old friend; the SRM-006tS.

The SRM-006tS is a high-voltage, low current amplifier designed specifically to drive electrostatics, it uses two 6FQ7/6GC7 double triodes and sports two sets of RCA inputs, one set of RCA outputs, and one set of XLRs. Although there are some really big guns from Stax now (most notably the large SRM-T8000), it remains the top of the tree for Lambda users, as the solid-state SRM-727II and valve SRM-007tII are designed ideally to match the 007 and 009 earspeakers. Personally, I think the SR-L700 is more than a match for these more up-scale energisers, but such a combination would tip the price tag into a new high level. 

, Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser

Revisiting the SRM-006tS does give us a chance to look to the new Kimik 2 modifications (as distinct from the original Kimik mods) performed on the previous version under test.

Nigel Crump from Symmetry still works with Mark Dolbear of High-End Workshop and Electromod (when not selling MrSpeakers and Schiit, Mark repairs and modifies products for Symmetry) to create the Kimik modifications, which all-in-all take about a week to complete. The old EAT tube dampers have been replaced by a new design from Bermuda Audio Tuning. In the SRM-006tS this is a two-ring damper, while three ring dampers are used in the SRM-007t II. As before, the two 6FQ7 tubes are cryogenically treated and matched precisely as a pair, and the case fuse is replaced with a Synergistic Research Red. This is felt to be a step up from the previous Kimik modification. Kimik 2 modifications are now an option on both SRM-006tS and SRM-007t II. There is no specific upgrade path for Kimik users to move to Kimik 2, although the logical step would be to invest in a set of two-ring Bermuda Audio Tuning dampers.

Judging by the boxes the products arrived in, ‘running in’ is an academic discussion because it happened some time ago. The review samples were well-used demonstrators it seems with some mileage on the clock. You may have to plug in and wait for a while for the true magic of this combo to unfurl itself, but I was lucky… I got both at their best from the get-go. And what a best it is!

The concept of the SR-L700 being a ‘SR-009 Jr’ is both entirely justified and playing down the quality of the SR-L700. What the SR-L700 has is that effortless midrange presence and clarity that the SR-009 has in spades, but by winding the specifications back a notch, the SR-L700 isn’t quite as uncompromising as its big brother. And that’s where that ‘grace’ part comes into play. What this Stax combination serves up is a satisfying view of music that’s just so captivating and elegant, all other considerations pale into insignificance. Yes, the pairing isn’t just about making music with grace, but that is so rare and so ultimately satisfying, you just keep being beguiled by that aspect of music played through this pairing. Oh look, another day went past with no notes on the pad, just a lot of musical enjoyment.


I can’t overstate this. Music is so satisfying, so enjoyable, so poised through the Stax SR-L700/SRM-006tS Kimik 2 that you find it hard to pull yourself away to perform other tasks. Any excuse is the instant justification to listen to a few more tracks – ‘I Want To See The Bright Lights Tonight’ by Richard and Linda Thompson from the album of the same name [Island] was playing in a scene in the movie Looperon TV. That led me to replaying the track through the Stax system, then reaching for ‘1952 Vincent Black Lightning’ from Richard Thompson’s Rumor & Sigh[Capitol], which itself led to playing ‘Sweet Gene Vincent’ by Ian Dury [New Boots and Panties!! Stiff], and so on and so on. That was a fairly typical evening’s entertainment for as long as the Stax was in place.

Then there’s the elegance of the sound itself. That calls for the Chairman of the Board. Playing the whole of the Come Fly With Mealbum [Capitol], you just sail through those Billy May orchestrations and Sinatra’s wonderful passing tones. That makes you reach back into Nelson Riddle territory and play Songs For Swinging Lovers [MoFi version of Capitol recording] and then on to Nat ‘King’ Cole, and so it goes on again. That’s the joy of the Stax system (and its curse for a reviewer of this Stax system); you just get swept up in the music, because it is played with such grace and verve.

, Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser

There is a stillness and a calming effect to listening to this pairing that’s not just Zen-like, but physiologically significant. I am prone to bouts of grinding my teeth (bruxism) at night when stressed, waking up with headaches and an aching jaw as a result. Maybe it’s coincidence, but every time I listened to some Beethoven or some Miles Davis through this Stax system, no matter how much stress I dealt with during the day, I slept soundly, and woke free from headaches, jaw aches, or having a mouthful of freshly-squeezed tooth. Sadly, we can’t prescribe this medically (“take two earspeakers and call me in the morning”), but the nature of the Stax’s poised sound makes it the perfect stress-buster, and considerably less ‘om-y’ than other methods.

Eventually, when you get past being enthralled by the sound of the system, you can begin to point to its strengths. The most obvious is the speed of delivery, and it’s that speed that makes you so enthralled with music. Listening to Richard Thompson’s guitar playing requires a system that can translate his dexterity, or potentially ruin the performance. Here, the Stax pair shine, and it’s like the man is playing live in your listening room. That speed doesn’t just apply to fast folk guitarists, it is needed universally; when you experience it, it’s hard to break away from its thrall. Other systems – even supposedly fast ones – sound sluggish by comparison.

Stax Lambda designs are traditionally placed in the ‘light, but fast’ camp, but the combination of SR-L700 and SRM-006tS Kimik 2 adds some muscle and heft to the bottom end. Let’s put this into context; organ music lovers and people who sign off emails with ‘Yours, in dub” are unlikely to see the Stax as bringing enough muscle to the bass, but this is about precision, not just power and paunch. The Stax combination has a fast, deep, and dry bass, more than good enough to keep most listeners happy. And those who seek fast-paced EDM tracks will need to work out whether they prefer the speed and resolution to parse those fast bass beats against ‘phatness’. Personally, I think I’d go with the Stax sound, because when I’m not playing Squarepusher or Autechre, I might be playing Mahler or Mozart, and I’ll take the clarity and refinement the Stax bring to the sound every time.

There is a good stereo stage, too, far more in line with conventional loudspeaker systems than many personal audio rigs. There is little sense of ‘lateralisation’ of instruments, and instead there’s a sense of scale and image width, and even solidity of instruments within a virtual stage. This is, I suspect dependent on the energiser, and it’s here where the latest Kimik modifications help improve the size and precision of that staging. Dynamic range is also predominantly a function of the energiser, and this scores high marks, too.

In absolute terms, the next step up the ladder gives you even more. In that respect, we are dealing with a ‘SR-009 Jr’ here, and the difference between the Junior version and the SR-009 proper is like the difference between having your car cleaned and having it professionally detailed. There is a level of resolution that is hinted at here, which the SR-009 (and a handful of rivals) lay open for inspection.


However, I can’t help but think this pairing of products represents the Goldilocks zone for electrostatics, and possibly for personal audio in a wider context. There are better, more detailed, more transparent, and more dynamic electrostatic designs out there, many of which have a Stax badge. All of which are more expensive; some, an order of magnitude more expensive. And, while these more expensive electrostatic designs do justify their place in the audio pantheon, it’s hard not to listen to the Stax SR-L700 and SRM-006tS Kimik 2 without hearing the phrase ‘the law of diminishing returns’. Although this law is said not to apply to audio (usually said by audio enthusiasts trying to justify spending the cost of a small yacht on a cartridge), I think there is a point beyond which improvements come in small increments at substantial price increases, and I think this pair comes in just on the right side of that point of inflexion. They have a synergy that makes the combination just magical, and hour upon hour of musical enjoyment are the result. For that alone, they would receive strong recommendation, but that they make this truly graceful, poised sound without the kind of lofty price tags one normally expects with high-grade high-end sound, means they are simply a must-hear. 

, Stax SR-L700 Lambda earspeakers/SRM-006tS Kimik 2 energiser



Type: Push-pull oval sound element, open-back, electrostatic headphone

Frequency response: 7Hz–41kHz

Electrostatic Capacitance: 110pF (including cable)

Impedance: 145kOhms nominal (including cable)

Sensitivity: 101dB/100V rms @ 1kHz

Maximum Sound Pressure: 118dB/400Hz

Bias Voltage: 580V DC

Weight: 496g (with signal cables)

Price: £1,195

SRM-006tS ‘Kimik 2’

Type: Vacuum tube output stage Low noise dual FET input Class A operation, Pure balanced DC earspeaker energiser

Vacuum Tubes: 2×6QF7/6CG7

Inputs: two stereo single-ended (via RCA jacks), one stereo balanced (via dual 3-pin XLR jacks)

Outputs: one RCA parallel output, five pin balanced headphone socket (×2)

Frequency response: DC – 80kHz, +0dB, -3dB 

THD+N: Max. 0.02%, (1kHz, 100V rms)

Gain: 60dB (x1000)

Rated Input Level: 100mV/100V outputs

Maximum Input Level: 30V rms at min. volume

Maximum Output Level: 300V rms (1kHz)

Dimensions (H×W×D): 103×195×375mm

Weight: 3.4kg

Price: £1,395 

Price (as complete package): £2,495

Manufacturer: Stax Ltd

URL: stax.co.jp

UK Distributor: Symmetry

Tel: +44 (0)1727 865488

URL: symmetry-systems.co.uk


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