[Moonwalker]

Hi!
 
Last week i purchased cheap, very old Stax system.
It consists of Stax SR-80 electret earspeakers and SRD-4 adaptor.
 
Price was about 50$, so I was expecting something belonging more to museum expositions, than anything resembling HiFi behavior.
 
I was pleasantly surprised by it's audio qualities if not by it's comfort on my head.
 
More details later...
 
Moonwalker

 

[reddragon]

interesting, along with impressions, mind posting pics too?

 

[vid]

Unlike with modern gear, in vintage audio you normally expect quite a bit for $50. And sometimes you get it.

 

[Moonwalker]

Well, i can take some pics, but i find them in very good condition, almost MINT.
They've been almost unused, the pads are still not cracked, cable is like new and the only thing needing repair was the foam on both sides and the yellow wool damper disc.
 
There was some dust, but i cleaned them using damp toothbrush when they were disassembled.
I was worrying about the cable material, but it seems pliable and undamaged after such a long storage.
 
Sound is nice, ethereal and with well defined soundstage, but sadly, until the sound hits the midbass range, around 80Hz, there is almost nothing to reproduce.
Highs are subdued, but smoothly present, and can be restored simply by turning the receiver's treble knob to it's +4 dB point.
 
Moonwalker

 

[Moonwalker]

This is an FR chart on ear coupler after some extensive testing and modding:
 

 
Unmodded, with absent, rotten damper foam and wool, there was pronounced peak at 200 Hz, up almost +9 dB, with second peak at 3000 Hz almost as severe...
 
Still, as you can see, there's nothing to hear except ambient noise below 80Hz.

 

[Moonwalker]

Hi!
 
Last month I detached old pads, they are really flat.
Now I'm using Sennheiser HD 205 pads, which fit my ears as circumaural.
The comfort went up a notch, for sure
 
Just small update...
Moonwalker
 

 

[Moonwalker]

Hi!
 
Yesterday I listened to few songs from Lobo and Rod Stewart.
 
I must say, they are nice to listen to, according to my wife, precise, and I concur.
It seems, though, there's a certain level in volume, lower than my usual limit, that seems to introduce strain , or compression to the sound.
I do not listen very loud, but when I'm tempted to enjoy some songs a little louder, the little Stax produces a sound similar to that going through soft dynamic compressor.
It was the same with oroginal pads too, and on 2 different amplifiers, Onkyo and vintage SONY.
 
BTW, HD600 are much more linear, dynamic, pleasant and NATURAL to listen, it's even dramatic difference when I switch them quickly.
 
My speculation is the transformers in the driver box are saturating, or the little electret is not very dynamic by nature.
 
Can somebody enlighten me in this issue?
 
Thanks
Moonwalker
 

 

[Moonwalker]

Hi!
 
Last night I measured the influence of the Sennheiser HD 205 pads on Stax SR 80.
Results are here: (cyan original, magenta Sennheiser pads)

 
Moonwalker

 

[Moonwalker]

Hi!
 
Last night I glued velour pads form Sennheiser phones, I think HD438. The velour ovals make them really different, and better.
 
The new pads are bigger, so the headset cannot be rotated (earpads outside) for storage anymore.
 
I think electrostats are almost always equipped with pleather pads to capture as muc bass as possible, the velours would make most of them predictably bass lean.
 
I also made circular damper, very similar to the mineral wool material originally used in the SR80.
Just a larger than the stock and I removed the thin foam from the plastic housing.
 
That made them really comfortable, and that is the main reason I can listen for the long enough to enjoy their qualities.
I will try to measure them sometime later.
Photos are already made, I just need some free time to post them here - DONE!
 
Just now, they are quite bright, quite sharp with quick attack, but smooth with prominent lower treble, but the otherwise dominant vocal range is tamed, as designed by STAX.
They are still not nearly as natural sounding as HD600, i can feel it's a reproduction all the time - but the kind I'm enjoying a lot.
 
Without proper damper, they become mid-centric, quite shouty, like old one-way speakers in large gramophon radios.
 
The change is not subtle, it ranges from interesting, but plaily old-school sound to really open, nice, if not truly Hi-Fi experience.
 
Moonwalker
 
Pictures of my SR80 with velour ovals:

 

[Moonwalker]

post removed - contained measurement of now unused velour pads, never to be returned...

 

[Moonwalker]

Hi!
 
I'm back to pleather pads, taken from Aurvana Live! headphones.
They are similarly comfortable as those from SenheiserHD438, but offer more low end presence, thus move toward balanced sound.
 
Also sensitivity is subjectively improved.
The SR-80 easpeakers clamp tightly to my head, causing mild discomfort after short time. They are much lighter than new STAX Lambda frames, but clamp just harder.
I will try to use them as much as possible to identify areas for possible improvement.
 
Channel balance with the Aurvana pads is still very good, mono sounds focused in the middle. Binaural record sound incredibly real.
 
Moonwalker
 

 

[Moonwalker]

Hi!
 
After a very long time, I decided to repair my STAX SR-80 a bit more.
 
There was slight bass resonance in left cup.
Also, the highest treble was weaker than I like.
 
So i detached the driver, held by 33 year old double sided tape.
Cleaned both the driver perimeter and platic baffle with ethanol.
Removed new foam in front of the driver.
 
The change in sound is too small to be detectable for me.
I used glue to for a ring on the front platic baffle plate and pressed the driver back in.
 
So far, the buzzing resonance is gone. The mod made them harder to service in the future, I'm afraid.
The same went for the other side.
 
Also I glued 5cm - diameter of the driver - wool disc to the backside of the driver.
Then a very thin 65 * 75 mm foam to cover rear grille.
 
Assembled them.
 
Still, they're deficient from upper bass to low bass, I compensate about +4dB on my amplifier.
Also, I add around +5dB for treble for most music.
Sometimes, I just forgot to set it and they still sound OK to me.
 
So, that's it, for nearly no price, other than a bit of the glue, they are just working again.
 
Just wanted to share my experience with vintage electrets.
 
Have a nice day!
Moonwalker