[Marco audio]

Bonjour,

Avez-vous trouvé les plans ?

Au départ, Stax a utilisé les prises SRC en bakélite d'un fabricant japonais.

Les broches des prises sont celles des XLR 3 broches.

Bien cordialement,

Philippe Hiraga.

Hello Philippe,

Thanks for your reply and explanation about xlr pins.
I bought a plug on eBay.It's works well.
Bravo and thanks for your l'audiophile pages about electrostatics stuffs.

Regards

Marc.

 

[Muamp]

Hi Wachara, all,
It has been a long time since I last checked out this thread, even longer since I built my last electrostatic headphone, although I am still very much enjoying listening to my 'stats.
Just spent a bit of time catching up on all the recent comments and designs on the thread, especially the ear bud 'stats! It is amazing there is always a constant stream of people taking up designing and building ESHS. It is fasinating seeing some great designs and new ideas.
David.

 

[ivanrocks321]

Hi Wachara. Got a question for you and was told you might know although its not about estat headphones but my friend Kerry G directed me to this thread to ask around.

I just got a pair of Peerless PMB 100 they are planarmagetic headphones and I was wondering if anyone including maybe yourself knew the pinout for these, they come with a 5 pin DIN "domino" connector. Was hoping to construct a pig tail to try to use them on some low powered speaker amps.

 

[chinsettawong]

Hi Wachara. Got a question for you and was told you might know although its not about estat headphones but my friend Kerry G directed me to this thread to ask around.

I just got a pair of Peerless PMB 100 they are planarmagetic headphones and I was wondering if anyone including maybe yourself knew the pinout for these, they come with a 5 pin DIN "domino" connector. Was hoping to construct a pig tail to try to use them on some low powered speaker amps.

I have no idea at all. Sorry!

 

[tib8]

Just to bring up a new topic: recently I read that one of the electrostatic headphone manufacturers using different method to drive the headphone:
They apply only aprox 140V of signal on the membrane, and put approx 3kV on the stators, this results simpler (single ended, lower voltage) driving electronics.
I decided to give a try for this configuration with the following hack:
DO NOT TRY THIS YOURSELF if you are not expert since HIGH VOLTAGES MAY KILL YOU!
I put the +/- 350V power of my amp on the stators and one side of the symmetric drive signal was connected to the membrane.
The result was exactly what I expected:
- due to the small CD voltage on the stators, it was weak (not loud at all!)
- my membrane has high resistance and this together with its few pF capacity forms a low-pass filter so the high freq was missing
- it had a big background noise (white/brown noise) - which is likely also due to the high resintance of the membran: we can hear how those few electrons pop on/off the membrane to change its potential...

So from the perfect driver it went back to the quality of the first transistor radios 60 years ago.

It is likely that using better conducting material as membrane and higher +/- voltage on the stators would solve most of the above problems, but I'm not sure.
(Also a single ended audio signal would be needed...)

What do you think?
Does anybody have more experiences with this configuration?

 

[lkos98]

Just to bring up a new topic: recently I read that one of the electrostatic headphone manufacturers using different method to drive the headphone:
They apply only aprox 140V of signal on the membrane, and put approx 3kV on the stators, this results simpler (single ended, lower voltage) driving electronics.
I decided to give a try for this configuration with the following hack:
DO NOT TRY THIS YOURSELF if you are not expert since HIGH VOLTAGES MAY KILL YOU!
I put the +/- 350V power of my amp on the stators and one side of the symmetric drive signal was connected to the membrane.
The result was exactly what I expected:
- due to the small CD voltage on the stators, it was weak (not loud at all!)
- my membrane has high resistance and this together with its few pF capacity forms a low-pass filter so the high freq was missing
- it had a big background noise (white/brown noise) - which is likely also due to the high resintance of the membran: we can hear how those few electrons pop on/off the membrane to change its potential...

So from the perfect driver it went back to the quality of the first transistor radios 60 years ago.

It is likely that using better conducting material as membrane and higher +/- voltage on the stators would solve most of the above problems, but I'm not sure.
(Also a single ended audio signal would be needed...)

What do you think?
Does anybody have more experiences with this configuration?

First I want to congratulate you for your enthusiasm to try this method (by the way I think it is called inverted ESL). Very nice!
Your observations are absolutely true, but I think the manufacturers did use different approach setup:
1. The membrane resistance should be very low and the stator resistance - very high - this removes the low-pass filter seen by the amp.
2. With 3kV the bias is high enough so the sound should be loud. Still with such high bias the isolation on stators must be very good - 0.3-0.5 mm - this adds to the spacing
3. Low resistance membrane is heavy, whatever the coating is. So it becomes heavier than air - we all try to avoid this at any cost with the ESLs. In other words - still not good with high frequencies.
4. Forgot to mention - with low resistance membrane - charge is concentrated in the middle - moving is no longer linear - distortion.
My experience with aluminium foil many years ago - please note I used low resistance stators (single side FR4) and low resistance membrane (aluminium foil):
1. I had to replace the output transistors of my amp every now and then, because once the membrane touches the stator it's a short circuit.
2. Because of the aluminum foil the phones got some kind of metallic sound.
3. Very unreliable with high surround humidity.
4. High total capacitance

 

[tib8]

First I want to congratulate you for your enthusiasm to try this method (by the way I think it is called inverted ESL). Very nice!
Your observations are absolutely true, but I think the manufacturers did use different approach setup:
1. The membrane resistance should be very low and the stator resistance - very high - this removes the low-pass filter seen by the amp.
2. With 3kV the bias is high enough so the sound should be loud. Still with such high bias the isolation on stators must be very good - 0.3-0.5 mm - this adds to the spacing
3. Low resistance membrane is heavy, whatever the coating is. So it becomes heavier than air - we all try to avoid this at any cost with the ESLs. In other words - still not good with high frequencies.
4. Forgot to mention - with low resistance membrane - charge is concentrated in the middle - moving is no longer linear - distortion.
My experience with aluminium foil many years ago - please note I used low resistance stators (single side FR4) and low resistance membrane (aluminium foil):
5. I had to replace the output transistors of my amp every now and then, because once the membrane touches the stator it's a short circuit.
6. Because of the aluminum foil the phones got some kind of metallic sound.
7. Very unreliable with high surround humidity.
8. High total capacitance

Thank you for your reply! Here are my toughts for your points:
1., 3., 6. The membrane resistance should be low, but not very low: only a few mA has to move in every direction of the membran permitter.
(Lower signal voltage on the membrane decreasing the required current even more!)
So a very thin gold coating for example should be more than enough (I know gold is heavy, but we need only a few nm thickness).
Since I do not have vacuum chamber at home to make such coating, "Emergency Mylar Thermal Blankets" could be a good first try.
It is 12um, which is 3x thicker than ideal, but still close to the target.
2., 5. Four layer PCB (FR4) could be used with copper only on the middle layers and with no galvanization in the grid holes.
Biger spacing is not a problem, can be compensated with even higher bias voltage, which is easy to provide (only a few diodes and capacitors needed on AC).
(This isolation on the inner side will protect the membrane driving transistors too.)
((Instead of FR4 an isolated + tensioned wire mesh could also be used, but I have no ide how to make it.))
4. In case of DC signal or low frequency you are right, the charge goes to the middle, but the charge has to come and go in every period, so on higher frequencies they spend more and more time on the way between the middle and the permitter... Should we also consider "skin effect" on higher frequencies?
7. I think humidity is not good for any electrostats anyway.
8. C = epsilon * A / d, I do not see here problem: the capacity is the same as for any normal electrostat. The good isolator may increase epsilon, bot the bigger distance compensates.

I whish I would have lot of free time to try this concept more seriously.

 

[ts8051]

My new Electrostatic Headphones.
Designed my me and 3d printed with PETG. The stators are circular in shape 1.5mm pcb FR4 single sided constructed with my CNC machine. The inner membrane is 2micron tensioned with weigths on a small table.

 

[chinsettawong]

Very nice! What is the size of the active area? How thick is your spacer? What amp do you drive them with?

 

[Ulfar4]

It is nice to see that there is always someone who is building new headphones.

I am using my last pair for about one year I think and I'm still enjoying them very much. There is only one negative about them, I have to recoat them after few months.
Now I printed out mylar stretcher, because my previous method was unrepeatable. And I want to test graphite coating, which could more reliable. I rubbed the graphite and it is working immediately on my test setup, but we will see after some time.

 

[chinsettawong]

Nice! Let me see more of what you guys made.

 

[ts8051]

Very nice! What is the size of the active area? How thick is your spacer? What amp do you drive them with?

The active area is 80mm in diameter, the spacer is 0.5mm as in stax and i use the standard stax amplifier.

 

[lkos98]

Thank you for your reply! Here are my toughts for your points:
1., 3., 6. The membrane resistance should be low, but not very low: only a few mA has to move in every direction of the membran permitter.
(Lower signal voltage on the membrane decreasing the required current even more!)
So a very thin gold coating for example should be more than enough (I know gold is heavy, but we need only a few nm thickness).
Since I do not have vacuum chamber at home to make such coating, "Emergency Mylar Thermal Blankets" could be a good first try.
It is 12um, which is 3x thicker than ideal, but still close to the target.
2., 5. Four layer PCB (FR4) could be used with copper only on the middle layers and with no galvanization in the grid holes.
Biger spacing is not a problem, can be compensated with even higher bias voltage, which is easy to provide (only a few diodes and capacitors needed on AC).
(This isolation on the inner side will protect the membrane driving transistors too.)
((Instead of FR4 an isolated + tensioned wire mesh could also be used, but I have no ide how to make it.))
4. In case of DC signal or low frequency you are right, the charge goes to the middle, but the charge has to come and go in every period, so on higher frequencies they spend more and more time on the way between the middle and the permitter... Should we also consider "skin effect" on higher frequencies?
7. I think humidity is not good for any electrostats anyway.
8. C = epsilon * A / d, I do not see here problem: the capacity is the same as for any normal electrostat. The good isolator may increase epsilon, bot the bigger distance compensates.

I whish I would have lot of free time to try this concept more seriously.

Don't get me wrong, I agree with what you said, it's just that for DIY it's very difficult to make light low resistance membrane. (as you mentioned the lighter you could find is 12um, so it's at least 4-5 times (including the gold) heavier than what we use here. High resistance stators shouldn't be so difficult to create - coating on a non-copper FR4.
Points 5-8 were for my experience with aluminium foil and low resistance stators - which is a terrible combination in my opinion. Capacitance is bigger than normal electrostatic headphones, because now the membrane is in the C equation (high resistance membrane is transparent for the capacitance stator-stator). Humidity was a big problem for me, because of good isolation - when there was a high humidity my ears were shocked with electricity, despite the megaohms resistors I had there.
By the way as I mentioned few times here, I use a different approach with my ES phones - pretty similar to these "inverted" ones.

 

[lkos98]

@ts8051
Beautiful. I see you used a light foam for the ear pads, please let me know how it sounds, does it seal good enough?
@Ulfar4
Great stretching jig. Is this a bicycle tyre?

 

[Ulfar4]

@ts8051
Beautiful. I see you used a light foam for the ear pads, please let me know how it sounds, does it seal good enough?
@Ulfar4
Great stretching jig. Is this a bicycle tyre?

Yes, 14 inch bicycle tire.