Vintage wine or stat of the art – a review of the present and past Stax flagship
By many regarded as the best current production headphone, the Stax SR-009 is already iconic. But so is the discontinued Stax SR-007mkI, also known as “Stax O2” was the former flagship of the Japanese electrostatic headphone maker. How does the old boy compare to the present “King of Stax”? Mr.Headphoneer and his fellow enthusiast Mr.Claus tried them out, using what they believe is Stax’s best current production amplifier (or “driver”, as Stax calls them) for the job, the SRM-007tII. We were both familiar with both headphone before this review, and in the following we will describe what we heard when listening to these great headphones, on track at a time.
Track by track comparison
Morissey – “Irish Blood, English Heart”
On this track, the SR-007 is richer, and fuller sounding, with a more relaxed presentation. The room feels smaller than on the SR-009, which is better at placing the instruments, it is really easy to follow every tiny sound, which is more precisely defined and presented in a bigger room .The SR-009 gives us a presentation that is lighter, with more focus on the treble. The SR-007 is creamier sounding, for good and for bad.
Emerson String Quartet – “Intimate Letters – Martinu: Poco Allegro”
The timbre of the strings are more defined on the SR-009, it gives a better sense of instrument resonances and the textured tone of wooden instruments. The soundstage is wider and more pinpointed. The SR-007 on the other hand has a very appealing tone, it is mellow and smooth, it is warmer and darker. On this track we couldn’t quite agree. Mr.Claus thought the SR-007 was good, but clearly preferred the SR-009. Mr.Headphoneer on the other hand, while accepting that the SR-009 feels technically superior with better separation, found the warmer, mellower and smoother presentation of the 007 to be compensating for this, preferring the SR-007 more.
Paavo Järvi/hr-Sinfonieorchester: Mahler “Symphony No.2 part III”
Also on the symphonic piece, SR-009 has superior separation. It is clearly easier to identify the separate instruments in the orchestra. In a superb way, the 009 brings the details upfront without overdoing anything. Although SR-007 has less of that superb clarity, it does the instrument tonality in a fabulous way. Especially on soloist passages where your attention is deliberately brought to one dominant instrument, this makes it a favorite. In complex passages the 009 wins on better separation and definition. You basically have to listen deeper into the music to get to the detail on the SR-007, but the detail is still there. On this track, Mr.Claus clearly prefers 009, but finds the 007 charming, Mr.Headphoneer really enjoys the smoothness and general tonality of the 007, the lush and sweet, yet detailed sound. In direct comparison he finds the 009 having a kind of “nasal tone” in comparison (lacking a better word), but recognizes the extra qualities of separation and texture from the 009.
Radiohead – “Go to sleep”
In the less complex beginning of this track, the sound of the SR-007 is really just nicer. It is full-bodied and smooth, more meat on the bone, whilst the 009 is thinner sounding. But when the music gets crowded the SR-009 excels as always with better separation and definition. It flows with superb ease through the busy parts, where the 007 gets a shimmery, glassy presentation, not giving the same sense of control.
Olga Konkova – “As Before”
Again SR-009 adds more of that magic air around instruments. However, the SR-007 gives a very nice and warmer sounding presentation, especially in the less busy beginning of the track. In comparison the SR-009 feels more clinical. The extra smoothness and fullness of the 007 suits this track well. Mr.Headphoneer clearly prefers the SR-007, Mr.Claus too this time, but less so.
To put it very simple: Both are exceptional headphones. They both have this amazing ability to make you feels that the sound is just there, floating in the air, existing on its own, rather than coming from the headphones you are wearing. However, the differences between these two headphones are clear and easily agreed upon, though preference might be different.
SR-007mkI is a very good sounding headphone, and it is indeed a world-class piece. However it definitely looses out to the SR-009 in complex passages, where it just doesn’t keep up with all that is happening in the same superb way as the SR-009. When the music is less complex or there is a clear solo instrument in the musical piece, this relative disadvantage is less apparent. SR-007mkI has relatively speaking a smoother, thicker voicing, but it is still sounding very much like an electrostatic headphone, with a super-delicate airiness that is hard to describe. The SR-007 makes you have to listen deeper into the music to get all the details, for some this is a pro, for some this is a con.
SR-009 simply feels technically superior, always having better separation, blacker background, more air between each instrument, more apparent texture. It handles complex passages with astounding ease. The way it effortlessly and gently accentuate details is just remarkable. It delivers a good punch when it shall and cannot be called bass-light. SR-009 does feels brighter and lighter than the SR-007 in general, though not in a peaky way or anyway near harsh. The treble performance is just stunning. It gives us a feeling of being neutral without being clinical.
Concluding the conclusion
All in all, we agreed that the SR-009 is the best headphone using “objective” criteria. However, Mr.Headphoneer really likes the voicing of the SR-007mkI better. For getting the ultimate in detail retrieval, the SR-009 is everything a headphoneer can dream of. But then there is that magical tone, the delicate voicing of the SR-007mkI. It’s just extremely charming. Charm is beauty, but so is perfection.
The test was done using a NAD M51 dac via XLR to the Stax SRM-007tII with NOS RCA cleartops tubes. When swapping headphones, we adjusted the volume level on the M51 DAC, finding by pure subjective measurement that the 007 needed 6-7 dB more volume to sound equal in volume. However, we kept adjusting this up and down when we found it subjectively necessary. Lossless CD-quality files were played from the Squeezebox touch.
The SR-007mkI is a discontinued product. It was replaced by the 007mkII which has a slight more treble presence, but is otherwise quite similar. Some prefer the mkI, some prefer the mkII. There are also known to be different unofficial variations within the mkI and mkII’s. But still, the difference between SR-007mkI and mkII are relatively small, and way smaller than the difference between any SR-007 and the SR-009. It must be added that there are some groupings of experienced and competent people in niche forums that constantly claim that the Stax amplifiers are not powerful enough, especially for the 007 mkI. Using a more powerful (and expensive) amplifier like the legendary Headamp BHSE might make the SR-007mkI sound more controlled. We cannot comment on this, since we have yet to hear any of the hard-core amplifiers. But the sense that SR-007mkI struggles in the complex passages might be an indicator of the amp not having enough juice.