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My DIY electrostatic headphones - Page 30

post #436 of 1522
Thread Starter 
Quote:
Originally Posted by dude_500 View Post

 

How would you seal them to the head? Mine are already about as big as I feel I could easily come up with earpads that form any sort of reasonable seal. Has this been done in retail (other than the ridiculous float headphones)?

 

My very first version has an active dimension of 7 cm x 10 cm.  The shape is oval though.  I guess going to 8 cm x 11 cm is OK, but 12 cm can be too long indeed.

 

I wouldn't call Float ridiculous.  In fact, it can be very good.  For electrostatic, size does matter. wink_face.gif

 

Wachara C.

post #437 of 1522
Quote:
Originally Posted by arnaud View Post

Wachara: maybe this is only the 009 then? See this picture: http://cdn.head-fi.org/e/ea/eaf088ce_DSC00274.jpeg

 

 

That is the textured PVC film Stax have used on all their drivers since 1993.  It's very, very thin and light but they never stretch it drum tight so it has no effect on the output. 

post #438 of 1522
Thread Starter 
Quote:
Originally Posted by spritzer View Post

 

That is the textured PVC film Stax have used on all their drivers since 1993.  It's very, very thin and light but they never stretch it drum tight so it has no effect on the output. 

Hi Spritzer,

 

Do you happen to know where we can buy it?

 

Wachara C.

post #439 of 1522
Quote:
Originally Posted by spritzer View Post

 

That is the textured PVC film Stax have used on all their drivers since 1993.  It's very, very thin and light but they never stretch it drum tight so it has no effect on the output. 

 

Thanks for the additional info Birgir, so this can be pretty much considered acoustically transparent. Do you know the reason for not going to thin fibrous material? Sweat or fear of small fibers getting into the diaphragm as time passes by? Somehow, it would seem like a suitable method further damp the diaphragm.

post #440 of 1522

Except for earpads (I'm planing velour), connector and some tuning (I'm planning to replace back-side dust cover for something similar as in SR-Lambdas to add some damping) I'm finished... o2smile.gif

 

1000

post #441 of 1522
Thread Starter 

Those look nice.  tongue_smile.gif

 

Where do you get the cable from?

 

Wachara C.

post #442 of 1522

Cable is ordinary flat cable from local electronics store but in black color instead of "rainbow" or grey ~1€/m.

post #443 of 1522
Quote:
Originally Posted by chinsettawong View Post

Hi Spritzer,

 

Do you happen to know where we can buy it?

 

Wachara C.

 

Not a clue but a thicker alternative can be found in those clear bags you can find at the super market.  The ones I buy are marked "Fruit Bags" and come on rolls of few hundred. 

 

Quote:
Originally Posted by arnaud View Post

 

Thanks for the additional info Birgir, so this can be pretty much considered acoustically transparent. Do you know the reason for not going to thin fibrous material? Sweat or fear of small fibers getting into the diaphragm as time passes by? Somehow, it would seem like a suitable method further damp the diaphragm.

 

Ever since the first SR-1 set all Stax sets had a film dust cover next to the ear and a woven one on the back.  There were usually three of them actually, one pressed up against the grill, one next to the damping pad and one on the back of the driver.  Fast forward to 1987 and Stax releases the first headphone without damping and they have issue with dust, major issues.  That's why they switched to film on both sides.  The HE60 also has the same issues due to it's dust covers which is why I add mylar or PVC to all the sets that come through here. 

post #444 of 1522

So I added some damping behind the copper-wire grill and it's now much better. o2smile.gif

Frequency response is now smooth (as far I can tell) without any noticeable peaks or dips (before that there was annoying non-flatness in midrange, especially annoing was ~1kHz peak). Also the headphones are now much less sensitive to good earpad seal because free-air resonance frequency dropped and the peak at free-air frequency response is much lower.

 

Anyone experimented with damping too? I'd be happy to know if there's any material that provides good damping but doesn't degrade soundstage, etc.

post #445 of 1522

Wow, this thread has really taken off since I checked in last!

 

 I'm still thinking about building another set of electrostatic phones. I'd really like to make this set special with an aesthetically matching tube amp to drive them. Something that would be visually along the lines of the SE 2A3 Morrison Micro I'm working on - http://www.audiokarma.org/forums/showthread.php?t=457931

 

I'll probably just set up a simple jig on my drill press for drilling the stators since I don't have a cnc.

 

What energizers are you using now for your headphones Wachara?

post #446 of 1522
Thread Starter 
Hi Matt,

It's been a long time. Beside the tube amp that I made long ago, I now have an eXStatA, Stax SRM007t, and a DIY T2. My next project will be a KGSSHV.

Since you already have an experience building the headphones, making another pair isn't going to be that difficult for you at all. I'm looking forward to seeing your creation soon. smily_headphones1.gif

Wachara C.
post #447 of 1522

AmarokCZ, what material and thickness do you use for the metal rods that provide structure to the headphones? I've been experimenting with some materials I have laying around and haven't yet found anything that I find satisfying.

post #448 of 1522

I too didn't found anything satisfying for long time. I tried some common steel wire (low tensile strength ~320MPa) but its elesticity is very poor. Reasonable choice is stainless steel (~700MPa) strip but you have to heat it before bending it if you don't want to loose its elasticity. frown.gif

But I knew that the result wouldn't be worth of heating-up the forge, so I asked my friend to get me (as he calls it) "spring wire" 2.5mm in diameter. It's high strength patented steel wire (~2000MPa), it can be bent cold and still its elasticity is reasonable.

It's good for the purpose, but it's nothing compared to the wires on AKG (K240, K270,...) headbands - you can bend them straight and they still return back to original shape (which is ~16cm circle). If you want something special just order some spare headband from AKG.

post #449 of 1522

Edit: updated graphs / corrected typos / added pics of the test rig

 

I have been making progress on my SR009 investigation... Got a measuring rig working reasonably well it seems so I now have proper data to calibrate my models! 

 

Here's the summary of what I've measured so far (had seal issue with the Omega 2 / plexiglass backing):

 

 

Repeatability check:

1000

 

 

Influence of backing plate used to perform the measurements:

1000

 

 

Comparison of SR009 and SR007A (driven from stock 727A amp). Omega 2 is end of SZ2 series, I did not (yet) plug the ports but bend the arch and springs as step gap toward mkI version. Obviously, there's still nasty boominess which is clearly audible:

 

 

1000

 

Free air resonance check:

1000

 

 


Edited by arnaud - 8/14/12 at 6:18am
post #450 of 1522
Thread Starter 
Hi Arnaud,

Do you know why the FR fall so sharply even before 10K?

Wachara C.
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