Potential fix for Stax SR-009 channel imbalance

[gspot]

I recently acquired a set of SR-009s that sounded like they had a bad channel imbalance, requiring a '2.5' - '3' adjustment dialled in for one channel on a 0-10 split-volume knob to yield approximately balanced listening. This shows the required left channel boost with right channel at zero:

With this correction, the headphones sounded more or less OK; but the left channel still sounded a little veiled/lacking body/fullness of sound compared to the right channel which worked fine.

Repair estimates were not forthcoming from Edifier/Stax (I'm in the UK, and these were purchased here) but the local official repairer (in fairness, without having the headphones in hand) suggested new drivers may cost around $2300... <gulp>

Feeling I had little to lose, I used some of the images in the 'Stax SR-009 Channel Imbalance Trouble / Driver Problem' thread and a little guidance from spritzer (thank you!) to remove the earpad, dust cover protection mesh and cable strain clamp cover to find one of the bridging wires which go between the cable proper and the connecting tab on the driver had come adrift/failed (they're black on black, a little hard to see, it's the bottom one in this photo):

Hoorah: no new driver needed! A friend of a friend (an experienced computer/electronics chap) soldered this wire back into place for me (I didn't trust myself to do this and keep the heat suitably low, getting it right first time), and the headphones now sound perfectly balanced and very nice indeed!

The other two tiny wires also gave way as we were re-assembling, so I'm posting this in case disconnected sacrificial strain relief wires may be behind some of the problems people are experiencing. These are quick and easy to fix if it's not coating/membrane failure...

 

[Whitigir]

So one of your wire was barely hanging on ? Congratulations on solving it !!

 

[gspot]

I was amazed when I saw it (or, didn't see it)! The wire was completely detached from the metal tab on the driver stator.

Equally amazed that the driver sounded as good as it did without this wire too!

 

[gspot]

Would appreciate any of the technically-minded folks explaining how the driver still sounded substantially OK without this wire in place. I've looked at the various simple stator/membrane diagrams but still don't quite get it (sorry). Is there a simple explanation for how it can work with one of the three wires not in play?

 

[Whitigir]

The stators are charged plate, the diaphgramps got fed an AC signals and will be pushed toward or pulled away from the charged plate. If one plate is not working, the diaphgramps would still function under this principal, even though you can say that it only is 1/2 of what it was

 

[muski]

I also had the channel imbalance problem with my Stax SR-009. Like you, with nothing to lose, I disassembled them and discovered that the tiny middle wire connecting the headphone cable to the driver was disconnected. Soldered it back and, much to my delight, no more channel imbalance.

If you decide to try this, take it slow and take lots of photos say you go. Pay particular attention to where the O-rings should be re-installed.

Cheers,
muski