By Svein Erik Bakken
Stax SR-Sigma and SR-4070
SR-Sigma
Writing about Stax and just the Sigma series could become quite a lot. I won’t elaborate too much, but this fascinating series deserves it’s own part in my story.
Stax spent about four years developing SR-Sigma and there was a lot of trial and error before they could present end end result. The Sigma was in a way the heart child of the Stax’s founder Naotake Hayashi and the goal was to avoid getting the sound image intimate inside your head, like other headphones did. They angled the drivers 90 degrees towards the ears like speakers in a room. This construction made the SR-Sigma series look somewhat different from the other upcoming Stax models. The Stax newly developed oval drivers was placed in front of you’re ears, as mentioned above, you got the sound image much like speakers. In addition you got a very wide sound image, which is why the SR-Sigma series is referred to as ¨electrostatic panoramic earspeakers¨
SR-Sigma, this came out in 1977 and is the first model to get the oval driver now known from the SR-Lambda series, this has a normal bias of 230v and was delivered with a black fabric cable. The grilles on the cups is light grey, the diaphragm is 2 microns thick. The sound image has somewhat muted treble reproduction, very good midrange and an incredibly wide sound image, good bass reproduction but somewhat muted and none existing real deep bass.
Stax SR-Sigma MK2
Stax Sr-Sigma mk2, came out in 1979, it was not an official ¨MK2¨ from Stax but they changed the fabric cable to a flat cable, more or less similar to the Stax cables of today. In terms of sound there is no significant difference from the first version. The first lambda uses the same driver as SR-Sigma.
Stax SR-Sigma Pro
This came out in 1987 and was, as the name suggests, a pro bias 580v version. It uses the same flat brown cable that also came on the SR-Lambda Signature with black grills on the cups. The headband and assembly is black. Stax further developed the oval drivers. This and the Lambda Signature are the only two models from Stax that have a driver with a diaphragm thickness of only one micron! This is simply unique! This driver was very difficult and expensive to produce for Stax so towards the end of production of the SR-Sigma pro a few copies were supplied with drivers from the SR-404 Signature. In addition the units that came in for repair got fitted with the SR-404 Signature drivers. The Sigma Pro i known for it’s very good midrange and bass reproduction, but is very hard to drive properly. You should use a powerful amplifier to really appreciate what these can deliver.
I can mention that the Sigma came supplied with it’s own grey headphone stand, while the SR-Sigma Pro came with a brown headphone stand.
Stax SR-4070
The SR-4070 series consisted of two editions and is Stax’s second closed model after SR-50 Electret. The SR-4070 really shows how much knowledge Stax has when it comes to producing electrostatic headphones. Here you have you have a closed model that sounds almost the same as Stax’s open models, how they have achieved this is simply incredible, in addition you get really good bass reproduction. These were intended for use in sound studios and were only offered as an ordered model. They use the same drivers as the SR-404 Signature. This came out in 2001 and have a membrane thickness of 1,35 microns.
Stax SR-4070 MK2
This version came along around 2005 and had a fork that attached to the cup with no swivel or movement. This made it a little difficult to adapt to some users and is clearly a flaw of design. In terms of sound these, along with the original have very high resolution with airy treble, large soundstage and a very good and deep bass reproduction.
Comments on the SR-4070
The first editions of SR-4070 were delivered with a numerical serial number, while the MK2 was delivered with both a numerical and alphanumeric serial number, but the easiest way to tell them apart is the design of how the fork is connected to the cup, and the fact that the MK2 have a somewhat duller finish.
Fun Fact
The Magazine cover from Stereo 10 features a STAX Sigma and a woman with a cigarette and a black eye. Why? The answer is that the photo is a reference to this ad:
“STAX listeners would rather fight than switch brands!”
Stay tuned for more history of this legendary company!
Check out the complete STAX history:
- STAX History Part 1
- STAX History Part 2
- STAX History Part 3
- STAX History Part 4
- STAX History Part 5
- STAX History Part 6
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