[wppk]

just : is my idea of the membrane of one driver being not tensed enough bad ? because I have no problem with another driver with the same voltage and same thickness.

 

[chinsettawong]

You are dealing with some very old headphones.  Many things going wrong aren't surprising.
 
I would try thicker spacers.  For pro bias, a total spacer thickness of around 0.45 to 0.5 mm is just nice.

 

[wppk]

yap. But I don't have a tool to measure that.
anyway, since my last test I wrote here, the faulty driver became stable. it works !!
I think now that there is no reason why it could not work fine anymore nor not be mendable.
thanks for all.
the sound is astounding. these are by far my best headphones. and I have quite a good deal of them, either static, ortho, or dynamic.

 

[wppk]

anyway, I do think that bassy srx (normal or pro) is coming from a membrane that has lost a bit of tense. just like when you tense a drum, you have a more or less bassy sound.
but, as you explained to me ago ( about lambdas) , when you don't have the good tension of the mylar, you have problems of stability and noises. I think it doesn't come from the tension, not direclty, I think it could come from the mylar touching or approaching the stators too much. as my brand new experience tends to show it. now, I have found, after so many tests, the good distance between the stator and the mylar, so it works, and I have no noise nor imbalance. what do you think of that ? does it make sense ?

 

[wppk]

I was fooled by myslef like a rookie...
The bass difference is not coming from the membrane being looser... but of course it comes form the pads. As I received the new ones today, I could change them on two srx. and then they had the same sound !
as I had tested different pads on different srx, I had lost the original sound. but, on the last ones I mended, I used the original pads, and it makes a bassier sound than with previous pads. That is stupid from me, because I should have realised it. My little excuse for itis that I lost the standard sound after making tons of tests. Well, this is not really the standard sound, as it is better when removing the black ring ( photo sent yesterday).
I also tried with these bigger pads I ordered and showed the link for. We win a bit bass, but the drivers get further from the ears and of course, we loose some "cristality" in the highs. So, I prefer them with the original pads. Ordered new ones already as mine are very old and need replacement. but impossible to find the real original stax anymore, or at a huge price if I remember well. and not being sure they really are available. ordered the good size for somthing that will hav a chance to be compatible. Couldn't find as thin as the original. I will see if it makes it or not, and what it changes.
one good news among bad : my last repaired stax still is perfectly balanced.

 

[Muamp]

Just finished a headphone listening test session.
Listening test general feedback:
Muamp#1 preferred aesthetically and acoustically. Muamp#2 not so extended at the top end, but Muamp#1 somewhere between SR007 and SR009, the SR009 having slightly stronger bass. Muamp#1 probably has better top end than #2 because it is completely open back, whereas #2 is only 70% open. Very pleased with the comments which will shape and direct my future builds. Muamp#3 will be Afromosa hardwood, but designed as #1.

David.

 

[ts8051]

Hello,
I also constructed ESL headphones with large membrane diameter 12.5cm and the case , headband, etc constructed with a 3d printer. The stators are 0.6mm pcb and spacing is 0.4mm pcb. The membrane is 2 microns. My question is for what reason is the central hole on stators?

 

[chinsettawong]

Hi ts8051,

If you don't mind, please show us your headphones. I'm very curious to see your rather large stator with only 0.4 mm spacer. I bet you tension your diaphragm extremely high. Do you get good bass out of your headphones?

About the larger hole in the middle, from my experience, it doesn't make any difference in sound. It's what Stax uses with its top of the line drivers and we're just trying to see what's so good about it. So far, I don't really see a good reason for it to be there yet.

Wachara C.

 

[ts8051]

Hello,
I can't send the images because i have no permission for this and I dont know how can i post these.
I tensioned the membrane with High tension.of course. The bass responce is incredible when i operate it with a transitor based stax energizer.

 

[Muamp]

I believe the hole in the middle is to facilitate maximum open area in the stator without loosing rigidity.
The extra open area from the centre hole can add about an extra 4% openness.
 
On a similar note, one thing I discovered last weekend from a listening test session with a group of headphone audiophiles is that my Muamp#2 suffers at HF in comparison to Muamp#1. I can only put this down to the wooden surround reducing the open back area from 100% in #1 to less than 70% in #2, since ALL other specs are identicle.
 
I am currently constructing #3 to be 100% open back with greater openness in the stator. Have to see whether it makes a difference.
 
David.
 
ts8051
You can post photos after submitting about 5 or 6 text posts.

 

[chinsettawong]

Hi David,

I also prefer the very open back design. Please try and let us know how you like it.

Wachara C.

 

[ts8051]

Hello,
I think that the center hole in stators minimize the active membrane surface because of absense of electrical field in this region.

 

[ts8051]

About the membrane tension.
I use a frame made of plexiglass. I apply the adequate piece of membrane and hold it with 3M tape. Then I apply tension step by step from all sides of frame with 3M tape until i cannot apply any additional tension. After applying the conductive material  on one side only, i attach the spacers with glue.

 

[Muamp]

After one more post, when you can add photos, I would very much like to see the tension frame AND your ESHS.

 

[ts8051]

The stretching frame is very simple. I was made of plexiglass.