Stax SR-3 back to life

[Pirx]

Hello

I bought pair of SR-3 year ago. I knew they had failure, left driver was quiet, right driver was only little louder.
After year I've decided to give them new life this spring.
At the first I've discovered holes in diaphragm of the left driver as you can see in the picture.
I decided to use 2um mylar to make new diaphragm for both drivers and self made coating with some antistatic spray+isopropanol.
Now I am sitting with them and writing this post, they sound great, with good bass, with sweet and not sharp highs.

 

 

 

 

 

Edited March 15, 2017 by Pirx
Refresh of pictures.

[Voltron]

Congrat

[DefQon]

Good job, with the help from wachara I also restored a completely dead silent SR-3N in the Stax thread here using the anti-static gel solution but since then have decided to make the fix permanent by using ESL speaker repair kit liquid compound from a local distributor.

[Pirx]

I've also restored drivers from Gamma Pro. Only coating was lost, and now they work great but I have no idea how long they will do.

New diaphragm in SR-3 sounds better than Gamma Pro with only new coating.

I wonder if in 1968 year in SR-3 Stax used mylar or something else?

Edited April 11, 2014 by Pirx

[spritzer]

They always used mylar until they switched to what I can only assume is PEEK.  None of the other plastics really work for this role...

[runeberg]

Hi all,

I'm trying to fix my SR-3 with severe channel imbalance (already confirmed it's the drivers and not the energizer), so I'm going to try recoating the membranes. I've removed the drivers and have gotten as far as removing the four copper pins - I can't seem to figure out how to take the rest of it apart. I'd thought when the pins came out the whole thing would just fall apart, but it seems rather tightly stuck, still. Is there a trick to further disassembly of this? Feeling rather daft. Thanks in advance for any help!

[spritzer]

With the pins removed the driver just pulls apart.  Some are pretty stuck and watch out for the wire going to the front stator.  It's an utter pain to fix if broken... 

[runeberg]

Mine seems pretty stuck indeed. Just to make sure I'm understanding before I go tearing away at it, the various inner parts just slide out of the outer plastic ring? Nothing's threaded in or anything?

[spritzer]

Well this is Stax so revision central but AFAIK the drivers have always been a larger outer shell and then the insert which holds the other stator.  The diaphragm is in the middle suspended on two metal rings. 

[runeberg]

Got it open! The outer and inner plastic discs were quite firmly stuck together, but I was able to get them apart after running a scalpel blade in between them, around the whole circle. Put on some antistatic gel, let it dry, and it does seem to be improved. Not certain it's quite right, still, but much better.

The ring with the membrane was stuck to the inner shell as well, so I only coated the top side - maybe that's my problem. Didn't see a clear way to pry it loose without risking puncturing the membrane.

Thanks much for your help, spritzer!

[spritzer]

I think the plastic may become conductive or do some other funky shit with age which might be a factor here.  Coating just one side should work just fine but check the bias point for corrosion. 

[runeberg]

OK, makes sense. I think it'll be a few days before I get around to opening it up again.

I realized also that I haven't confirmed the energizer is putting out the right bias voltage. Since the two channels are biased in parallel I figured it wouldn't be a consideration, but maybe if the bias is low the two would react differently.

Such a finicky beast, but I'm quite enjoying even the flawed sound.

[chinsettawong]

If you open them up again next time, please take a few photos of the inside to show us.

 

 

[spritzer]

Indeed, always interesting to see if there are any variations in the design.