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My DIY electrostatic headphones - Page 41

post #601 of 2527

4-day weekend, so I figured I'd finish these up so I can stop being distracted by the project. After about 16 hours over the last two days, out come my omega clones.


I decided that I should etch away that copper. I just did a standard toner transfer lining it up by eye. Upon typing up my last post, I realized it'd be correct within a millimeter or two, which is more than enough precision for this.



Next, I assembled the plastic mount for the earpad. This is made of 1/8" ABS as the rigid structure, with a 0.02" styrene spacer and a mounting loop of the same thickness. The slit allows for the earpad to easily rotate into place:




Diaphragm's were made by my typical method of hanging weights as I've discussed earlier.



Next, I cut a spray mask on a styrene sheet and airbrushed elvamide solution onto the mylar. The mask is to keep the elvamide off of the edges to prevent any leakage of charge. I really like the airbrush technique... hook it up to a compressor, spray uniformly, and in a couple minutes of work effectively perfectly matched coatings can be accomplished.



I used my crumpled mylar sweat screen design, since it seems to be completely acoustically transparent:



And, the final product:





I need to play with damping a bit, may need to add a felt sheet to the outside. But that's it pretty much.


Weighting in at 0.60lbs, they feel weightless compared to my previous builds (in fact they can be comfortably worn with the elastic head strap not present just pushing against the ears). Free air resonance is 75hz.


I'm not going to bother posting analysis graphs yet, since honestly I'm too tired to even think about analyzing them. I'm going to play with damping first anyways since there is some distortion in the 300-600hz range as is typically seen in fully undamped headphones.



As for the sound, they are fantastic. noticeably better than my previous rectangular builds, I imagine largely due to the quality earpads (a purchase that I most certainly do not regret!) and the large driver area.



This will probably be the last pair of headphones I make in the foreseeable future (right... like that'll happen).

post #602 of 2527
Thread Starter 

Hi Dude_500,


Congratulations on your fantastic build.  Your headphones look great!  I'm sure that they sound great too.


Since your active diaphragm diameter is 88 mm, do you have any problem with the stability of the diaphragms?  


I'm looking forward to seeing a lot more DIY headphones from you.  wink_face.gif


Wachara C.

post #603 of 2527
Very nice Dude. What's the weight of those?
post #604 of 2527
Originally Posted by .Sup View Post

Very nice Dude. What's the weight of those?


Originally Posted by dude_500 View Post

. . . Weighting in at 0.60lbs, they feel weightless compared to my previous builds (in fact they can be comfortably worn with the elastic head strap not present just pushing against the ears). Free air resonance is 75hz. . . .

 Or 0.27 kg if we're talking metric.

Edited by Soul_Est - 10/8/12 at 7:40am
post #605 of 2527
Thread Starter 

Hi Dude_500,


Do you put a dust cover on the backside of your driver?  From the picture, it looks like you don't.  


For damping, I know I few people who build their ESL attach a piece of cloth to the stator.  They really glue the cloth on the stator. If you want to, you can try that.


As for me, I don't like any damping.  I feel that it adds coloration.  


Wachara C.

post #606 of 2527

As for stability, I haven't had any problems yet, but time will tell. I increased the tension over what I've used on previous headphones (that tension was hopeless for such a large diaphragm) and it seems pretty stiff, so I have pretty good hope that it'll remain stable. I'm shocked how low the resonant frequency is, I guess it's related to size as well as tension.


In the past I haven't liked damping, so I most likely won't add anything. I do hope to find a grill to put in, though. Do you know of anywhere to get those circular grills with the bent lip that can friction fit into a hole? I'd even go with a custom order if it were affordable.



Interestingly, I still have a 1.5khz resonance and bass rolloff below it! L/R channel:



I really need to figure out some way to get rid of that phenomenon, it definitely affects sound. I think I'll carry my amp to the shop today to test and convince myself it's not the amp that's causing the rolloff, but I'm guessing it's fine since I've tested it many times.

post #607 of 2527
thanks soul, I missed that!
post #608 of 2527

Is there perhaps something bad about having too little tension that I'm not aware of (other than losing stability, of course)? It seems every pair of headphones I make is worse than the last, and these are about as bad as it's gotten on frequency response. There's pretty much no bass there at all. In general, the FR seems to ramp up at about 3-4db/octave up to 1.5khz, which is obviously not a very pleasant listening experience.

post #609 of 2527

Lower tension = better bass, because of lower resonance frequency. As proof I had a pair with extremely low tension (diaphragm sticked to stator even at 230V at certain conditions), but the bass was amazing even with bad sealing. By the way: SR-404 has free-air resonance frequency 207Hz and bass is super flat (just like on my headphones).

post #610 of 2527
Have you tried to tape the edge of the earpad along the sim with the driver frame? I am wondering about leakage there as I don't understand your pad mounting method. Another possibility I want to investigate is stator effect. what is the stator thickness, material, holes diameter and holes separation distance?
post #611 of 2527

Tape didn't change anything. I think it's a pretty good seal.


Stators are 1mm FR4, holes are spaced at 0.155in from each other and have a diameter of ~0.115in (was supposed to be 0.125 but the router made them a bit smaller, don't have calipers around right now).



I'm going to try making stators with more tension to see what that does. I had a pretty sparse covering of elvamide and added some dish soap (I know, not a good long term solution... just wanted to see how it'd affect it) and it instantly goes unstable with that coating, so I guess more tension will be good regardless.

Edited by dude_500 - 10/9/12 at 3:54pm
post #612 of 2527

dude_500, what is the overall diameter of the fr4 stator and diameter of the perforated area?

post #613 of 2527

post #614 of 2527

I doubled the tension (blue line) and it's pretty much the same, so it doesn't seem to be an issue related to tension.


post #615 of 2527
Thread Starter 

Hi Dude_500,


What's wrong?  I thought you liked them.  You mentioned earlier that the free air resonance was at 75Hz.  I thought that was terrific.


Why did you rebuild your diaphragm?  Did you run into instability?


I don't like using dish washer.  While it's alright, it tends to absorb moisture in the air.  Is alvamide not working very well?  If you want to try something different, you can try a few drops of black ink or antistatic gel into your alvamide solution.  I think they work better.


I notice that the two frequencies response curves are very much different from one another.  Do you know why?


Wachara C.

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