At £3495 the Stax SR-009 headphones are intended for the committed headphone listener. For Hifi Pig’s ongoing « Headphone Month » Janine Elliot takes a listen…

The thought of swapping the review of a £60 pair of headphones to a £3,495 Stax monolith was like getting out of a 2CV and taking off in a McLaren F1. There was just going to be no competition. So, what I decided to do in this review was to compare the SR-009 with the £495 SR 407 (see separate review), combined with the £1,295 SRM-006tS and £2,295 SRM-007t ll Kimik vacuum tube energisers, which are needed if you wish to hear any music. The Kimik, with its play on the letter K (just like Linn), is £200 more than the standard 007t ll, but has better quality selected old/new stock 6FQ7 cryogenically frozen tubes fitted with EAT dampers, and the pins are 24 carat gold plated. Before getting to the customer the bias and balance is adjusted over a five-day period. Lots of TLC, then.

The SR-009 is the flagship of the extensive range which starts with the £275 in-ear SR-02. Whilst I personally prefer the gold finish of the cheaper SR-007, the conventional shaped aluminium SR-009 is of improved build quality. This ear speaker was pure class. Lambs wool, and a comfort that makes the plasticky, rattley, rickety, cheap finish of the SR-407 feel more like something from another manufacturer. The SR-009 differs specifically from the £1500 cheaper SR-007 in that the drivers are angled, as in the Lambda based’ 207/307/407/507 fraternity. Believe me, this extra £1500 is worth every penny in order to gain a more realistic soundstage in front of, rather than inside, the listener! Similarly the SRM-007t II Kimik is the very top of their range, though I personally think the additional two valves duplicating the output circuitry somewhat veils the sound quality. I believe in keeping things simple.

For those unaccustomed to Stax ear speakers, the sound is generated between two “parallel-arranged fixed electrodes” – the electrostatic transducer -between which is suspended a low-mass, high-polymer film that is less than 2µm thick. This is basically a push-pull driver system. When the fluctuating voltage of the audio signal is applied to the electrodes the diaphragm is pulled and pushed. With frequency response from 5 to 42,000Hz and a maximum sound pressure level of 118dB, this needs a premium source fed into it to even start to appreciate its sound quality.

Whilst the product has gone through the most extensive research and building, commemorating 50 years of its electrostatic ear speakers (excluding electret models), the sales brochure is a lot more confusing. I mean, tell me what all this is about;

“It will exactly be as a result of “work” each predecessor piled up, if a race, a company, and an individual have “pride”. And it clearly depends on the way of life we live now to inherit it and to bear “enhancement” and “evolution”.

Just saying a lot of pride and craftsmanship has been put into what is our most iconic and best ever ear speaker would have been good enough for me. Luckily the posh-card manual inside the wooden-box-adorned SR-009 was a lot more specific. At the outset I have to say that this product is nothing short of ‘out of this planet’. The head pad is extremely comfortable and, unlike the SR-407, has a lockable slider mechanism for different size heads that actually stays put when you’ve set it. Comfort matches my favourite Audio-Technica ATH-W1000X, but that is where the comparison ends.

So to the tests. First of all I listened to both Stax models through the cheaper SRM 006tS energiser, with Krell KPS20i CD and Townshend Rock 7/Merlin, Rega/Ortofon Kontrapunkt, Manley Steelhead vinyl. After this I used the Kimik energiser.

Playing Eva Cassidy ‘Fields of Gold’ was mind blowingly open. The cheaper energiser had a thinner, brighter sound and made the difference between the SR-407 and 009 greater than when both were fed through the Kimik. The sound in both ear speakers was highly accurate, with the guitars sounding as bright as the title in the song, Golden. The SR-009 had far more space between instruments and the singer; I mean in front of me, not just middle, left and right. Listening to a live version of Dire Straits’ Private Investigation there was a wider ambiance and I felt I was in the audience. The SR-407 were claustrophobic in comparison, even though compared will most other gear out there the SR-407 is streets above. I would be scarred for life (if you’re my age and know the words, you’ll realise the play on words here….) if I had never listened to these marvels. This was not confidential information. Enough.

Bird song repetition between the first and second violins in The Four Seasons was much more open and crisper, and therefore easier to listen to in the SR-009. There was more in front of the listener. The Battle from The Gladiator was far cleaner on SR-009; open, precise, easy to listen to, but more than anything, musical. The sudden loud ‘rages’ don’t sound as muddled or as heavy, even though there is more bass, as they do on the SR-407. Yes, more bass apparent on the SR-407 than the SR-009! The thing is, because the sound is more muddled on the SR-407 you think there is actually more of it! Believe me, the SR-009 is not lacking in anything. The sound is further forward from the ears. A sudden edit at 5’17” mid-phrase has an increase in level that the SR-407 can’t pick out. Indeed, it is more noticeable through the SRM-006tS than on the Kimik. Indeed, if I were to make a really radical statement here; I actually prefer the £1000 cheaper SRM-006tS! Interesting then, perhaps, that Stax themselves are presently designing a new energiser to replace/be an alternative to the SRM-007t Kimik.

Vocal “ums” in Jennifer Warnes “Bird on a Wire” (Cypress Records 258418) were much clearer identified in space. The whole soundstage appears much less cluttered. Donald Fagan “I G Y” from the album ‘The Nightfy’ (Warner Bros 923696-2) made me wonder how much I had been missing for 32 years. The clarity, in a rather clinical track, was as if my ears had just been syringed. I didn’t realise CDs could be this good; power, channel identification, frequency response. And in the 32ft pedalboard of the organ of Nicolas de Grigny – Recit de Tierce en Taille (Dorian DOR 90134) couldn’t be any clearer, or deeper. Nothing could get past these, not even the real canons firing off in Tchaikovsky 1812 overture (Cincinnati Symphony Orchestra, Telarc CS 80041). In contrast Deep Blue Sky from John Lee Hooker was so laid back with velvety warmth and musicality that I wondered if life could get any better.
So, to conclude, the SR-009 are the best sounding ear speakers, cans, headphones, or whatever you or Stax want to call them, that I have had the pleasure of listening to. They, combined with the Kimik, were well worth the combined £5,790 if you wanted the very best in sound quality. If you were to spend money on a comparable loudspeaker based system, expect to spend £30,000 plus. If cost were an issue, then I have shown that the SRM-006tS, at £1,000 less, is more than a match for these cans, and I actually did prefer them in much of my listening tests. The SR-009 and energiser do need significant run-in to get to their best, but even at their worst were as exciting as UK importer Nigel Crump, Symmetry, sounded every time he talked to me about them. He has every reason to be very proud.

Janine Elliot

Sound Quality – 9.5/10
Value for Money – 8.5/10
Build Quality – 9/10

Overall – 9/10