THE SIGMA/404 A NEW STAX HEADPHONE?

Well... yes and no. What I have here is an old Sigma, modded to the standard of the current Stax 404. It is a new design although it's never been commercially made. Here's the story.

The original Sigmas came out in 1977 (see photos of original model)



In 1987 Stax re-issued the Sigma to the high bias or "pro" standard, with a 580 volt bias versus 230 for the old model and with I believe more spacing in the diaphragms to allow greater excursion. The idea was to give the phones more dynamics, particularly with the upcoming arrival of digital recordings.

There was otherwise no basic difference between the original and the pro Sigmas and for some years after 1987, Stax would convert the originals to pro specs for a few hundred dollars.

I had 2 original Sigmas. After one became physically damaged I had it converted to "pro" spec. By this time only Stax Japan would do the modification.

A few years ago my last original Sigma developed serious faults, a bad cord and a broken headband and I put it away. This was no great loss since its amp, an SRA12S was also somewhat non-functional. Earlier this year I decided it was time to do something with them and to see if I could again persuade Stax to repair/mod them to "pro" standard before all the original parts were gone.

However, by now, Stax had moved on from the "pro" standard. All new phones are "pro" standard, but since 1998, with the advent of the Omega II, the new designs use thinner diaphragms as well. (The Sigmas were long out of production by now so there are no production models of a Sigma with these diaphragms.)  (EDIT I have since discovered that the Sigma Pro uses the Signature driver which at 1 micron  is the thinnest , ever made by Stax)

I contacted Stax Japan to see if they could mod the old Sigma up to the newest standard, basically a Lambda/404, i.e. 404 drivers and low capacitance cord. After some prodding they turned the job over to YAMASINC., the American distributor.

So the result is now warming up on a Stax SRM-3 amp in my office, (they will be used with a Stax 717 at home.)

My first impressions are that these phones sound just like what they are: a 404 in a Sigma enclosure. They have a somewhat peaky midbass characteristic of the Sigma (and due to its enclosure,) and the somewhat attenuated high frequency of the Sigma enclosure, but with a bit more treble at the very top and a bit more detail, than either the original Sigma or the Sigma pro ( and characteristic of the 404 diaphragms and cable.)

The plus factors for this design are the enhanced out-of-head/forward projection caused by the Sigma enclosure, which it obviously has in common with the older Sigmas, but with the detail and treble extension of a 404. What it doesn't have is the sometimes grating treble peak of the 404, due to the high frequency attenuation caused by the Sigma enclosure.

So is this truly a new model? Yes, as much as any new/upgraded model, such as in going from the Omega to Omega II or Lambda Nova to 404. Of course it is not and never was a production model, so you can't just go out and buy one. In fact, Tats the tech at YAMASINC told me they had not made one like this before. But presumably they would be willing to do it again if presented with an old Sigma to work with.

The basic conversion was a bit over $500.00, a bit more than the cost of getting a 404 from Japan these days. Since the headband (Stax calls it an "Arc assembly") also needed replacing it pushed the price up some more.

I have since also repaired the Stax SRA12s amp and bought an old original Sigma, so I now have three versions of the Sigma series.

I hope to give a more detailed comparison of these three Sigma designs and possibly compared to the 404 and lambda Nova in a week or so.

Looking forward to more impressions on this hybrid pair. Good to know that they can still do repairs (at least in some way) to older models, as I've been thinking of picking up a pair of Sigmas at some point.

We want photos!!!
I just emailed Simply Stax and they said that the Stax importers had told them the conversion would be very difficult if not impossible! Maybe I should contact Yamasinc - I have a Lambda Nova Signature that could be used for parts...

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I don't know what their problem is in doing a conversion. YAMASINC offered to do either of two conversions, a simple Sigma Pro upgrade using SR-202 parts for $300.00 or the SR-404 upgrade for an additional $160.00. All the parts to be provided by YAMASINC. All plus tax, labor and shipping. In fact the only original parts left on this set are the Sigma diaphragm enclosures.

A few hours into a warm up and the new Sigmas are sounding very good compared to a Lambda Nova, using the SRM-3, very full bodied in the lower registers, while the Novas are left sounding somewhat thin by comparison.

As regards photos, am I missing something or do you need to post them first on the internet? At any rate all the phones look the same, i.e. they all have the same enclosures. They do have different cables and the Sigma/404 has a different Arc assembly, actually a Lambda Basic. Apparently Stax no longer has the original Sigma assembly, which is exactly my point as to why I wanted to do the job now, before other critical parts are gone.

Use Image Shack or Photo Bucket to upload the images - I would like to see these with the new parts fitted (ie the new headspring and cables). I would not need these - a Lambda Nova Signature/Sigma (cable and diaphragm assembly) parts swap is more what I need.
....and maybe you might like to post a photo of you wearing them
I have done so, so why not you?
Do you still think the low bias phones are in the same league?

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No way am I going to post a picture of me wearing these suckers on the internet. It would follow me to my grave. Their sound is great, their appearance is yuck.

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I think this fear is what stopped many a potential Staxinator from buying these things back in the late '70s. Thinking back, the only other headphone that might have had the same approach-avoidance effect on buyers was the Stanton Isophase electrostatics of the early '70s.

If I could get a hold of a broken pair of sigmas, Id be more than willing to have them cannibalise my SR-202s and create one of these hybrid pairs.

And unlike most other people, Im willing to post a picture of me wearing any headphone.

They have a black ops look to them. Nice. You could rent them out
to various tv series and movies.

Did you ever hear of President Dukakis? Well here is one reason why.

"Arc Assembly?" Hellooooo, marketing dept.

Someone should tell Stax that when describing a product that sends volts right next to the user's head, "arc" is really not the word they are looking for.

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Maybe it's an oblique reference to how outdated their headband assembly is. eg. 'state of the arc'.

OK, I'll accept photos of just the phones minus you, but I really would like to see what they look like modified before I think further on modifications by Yamasinc.
How do they sound with the 717? I'm still liking the low bias set with the SRM1 Mk2. It has a lot more oomph in the low end than the LNS, but the top end is still a little too rolled. I don't think you can beat the Sigmas for voice and lack of sibilance however. If the modification gives the Sigmas more dynamics, less rolled top end while leaving the positives intact, I may have found the perfect phone, and I'll abandon the Omega (and I can then use the 717 with the Sigmas - they need lots of power to come alive, and I suspect you will like them better on the 717 than the 313).
If posting, could you post pictures of where the headphone cable exits the driver housings as well as the modified driver casing that had to be drilled out to take the 404 arc assembly. Although my arc assembly is intact, it would be interesting to see what Yamasinc had to modify.

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I will work on photos and a full review but not right away. I think these kinds of phones (and probably many other kinds too) need a significant break in, say 2 or more weeks of regular use before they settle down to stable characteristics. To make more sense of what they do, I would want to make comparisons of the three Sigmas, and the Stax 404. That's a lot of comparing. BTW do you have a set of Omega 2' s? If so I would be curious about the tonal characteristics of the O2 vs Sigmas.

Actually from the outside, none of the three Sigmas looks different from each other, except for the cables. I will have to look inside the enclosures to see if there are any significant differences. YAMASINC acted as if the modification was pretty easy. Possibly Stax Japan had some kind of kit to do it.

As regards their sound, in the middle of the evening last night, they started to really sing on the 717, but when I changed over to the SRM-3 they still sounded about as good. The 717 handles them a little better with more clarity and impact and a bit more bass and treble but the SRM-3 is not too bad. The SRM-3 does seem to take longer to warm them up however and the amp seems to struggle a bit for the first 20 minutes or so. And there is still no doubt in my mind that all the Sigmas, because of the unique positioning of their diaphragms produce a desireable amount of externalization of sound, which no other phone seems to be able to do.

I would say that compared to the original Sigma pro, they have more clarity and a significant increase in treble. They sound a little warmer and sweeter. I don't know that there is any improvement in bass, but the general cleanup of sound may make the bass seem clearer too.

Compared to the 404 and Lambda Nova (I have been mainly listening to the Lambda Nova at this point) I am struck mostly by the lact that the Sigmas/404s lack the mid-upper peak (about 2-4kHz) of the Lambda. In fact it is quite jarring to hear the Lambdas after the Sigma/404 and I now more fully understand why some people, who are not used to them, don't like the various Lambdas.

With the Sigma/404's there are more highs than with the other Sigmas, but the tonal balance is probably more acceptable to most listeners than the Lambda sound which is by comparison much brighter. The Lambdas put you close to the performers, with the right recording this can be glorious, with poor recordings they can sound thin or harsh.

The Sigma/404 has the same prominent mid-upper bass as the older Sigmas. However I decided that I didn't mind this before I decided to invest money in the conversion. It's not an accurate phone in this respect but it is "euphonic," to use a term that has become popular in these forums of late, by which I mean that it may be a desireable type of distortion or innacuracy because it adds more than it takes away. In particular it leads you to do more toe-tapping in time to the music, something the Lambdas don't really get you doing.

However, the Lambdas give more really deep bass, but there's not that much of these sounds (eg. double basses) in most types of music.

I am actually quite relieved that they are working out so well. As it got closer in time to the receipt of these phones, I was getting nervous as to wether they really would sound ok. Maybe the 404 parts just wouldn't work with the Sigma enclosure. I couldn't send them back, after all I ordered them that way. But in fact the characteristics of the Sigma and 404 seem to complement each other.

Thanks for sharing - I am starting to think that a conversion may be in the nearish future. I don't have the O2 - deciding on whether to upgrade the Sigma or go for an O2 at the moment. I like the sound of the Sigma - it's quite addictive, but it needs a little bump up in the live ambience range - i.e. it's more difficult to hear crowd noise on the Sigmas than the Lambdas. The hybrid sounds like it could be nearly ideal. Hopefully vocals remain avocado smooth (waxing lyrical here) without the slight spittiness of the Lambdas. The bottom end of these phones sounds louder to me than the Lambdas, but not as deep. It adds a rockin' bottom end that makes music a little more interesting than the more cerebral Lambdas. If Yamasinc get back to me with a reasonable estimate, I can then think about selling the SRM 1 Mk 2 Pro. If not, O2s could be in the future (or maybe BOTH ).