Stax SR-007 Quality Control Issues

All Stax are equal, but some Stax are more equal than others

In this article, I want to expose the several differences among Stax headphone pairs. I won’t name sources, but information comes from Stax dealers across Europe, as well as other findings, experiments, among which I also was involved.
One English company, selling Stax equipment, ended up closing down their business due to Stax’s poor quality control (in fact mainly on the SR007 headphone in particular which was his best seller).
Although the word on Hifi forums (Head-fi in particular) is often that differences among pairs come from worn earpads and other issues, I and others have a very different view. All other things equal, there were SR-007 examples sounding mediocre and others wonderful.
This is coming from a guy who has heard a lot of them and dealt in them. It was bad enough for him to close that business.

I’ve so far personally heard 3 SR-007 with my own gear and they all sounded quite different. Only one was really good and worth its fame.
Other friends of mine (from UK, Huungary and so on) didm also “sampling” on several SR-007.
Initially, we thought that only the first batch of production (7xxxxx Serial Number) was good, and lately word has been spread that Stax changed their drivers to slightly cheaper ones for the SZ1xxxx production (still recognized as SR-007 Mk1) — this idea (which I and two mates had been advancing a couple of years ago), has been widespread lately from some of the most knowledgeable Stax enthusiasts, who, until 1-2 years ago, used to neglect any differences among all the Mk1 runs, at all.
In fact, the assumption which I and others had been bringing on isn’t accurate, and there is much sound quality variability even among the very first production examples.

This means that there are SR-007 Mk1 that sound dark, lifeless, and so on, and it’s not going to depend on amplification alone. The best sounding SR-007 I had was fantastic out of a SRM-007t, which is usually badly regarded for the Omega 2. The detail, dynamics, vibrational bass depth were all fantastic. It was kind of V shaped (so, midrange not ideal by taking it alone), but it was immensely transparent and layered.
We have been maintaining serial numbers. I will keep this article updated, and will be posting them.
You can email me for further questions, at tony – at – soundbsessive dot com.
Other people (source: have spotted further variability in normal bias Lambdas, comparing 4 pairs and finding several differences.

I have seen many people give up on Omega 2 by blaming it on their need for huge amplifications, but really, I am more and more prone to believe that the only way to incur in a good pair is just by trial and error, and then keep the actual good sounding one(s).

To be continued…