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My DIY electrostatic headphones - Page 36

post #526 of 1547

I know you don't sell them but I'd be up for something like that soon.  I guess I'm just bored with the commercial stuff...  redface.gif

 

The HE90 project has been stalled because my stash of drivers has shipped from Japan yet.  Partially my fault because I keep buying more and more stuff... tongue.gif  It should all ship next week so impressions due soon

post #527 of 1547

This thread is Head-Fi's truly well hidden gem. Just read those all 36 pages with much interest and awe, within a period of 3 hours or so. You guys give a whole new dimension to this hobby. To think that someone can so easily build something that compares to the $5k 009 with such inexpensive materials is quite staggering. I hope you guys allow others to have a taste of your creations in future meets. It would be a real shame if the only people allowed to experience such fine fruits of labor be those who built them.

 

Anyways, here's an idea for your future creations. Regarding the issue of sweat/vapor guard (even though you guys seem to have it mostly solved), take a look at this neat product:

 

 

Spray this on a thin fabric (perhaps pantyhose) then use that as your guard. It should repel moisture far better than the mylar film, while being air-permeable!

 

Mr. Chinsettawong, kudos to you, Sir, for being the pioneer, as well as being so willing to share your knowledge and experience. smile_phones.gif

post #528 of 1547
Thread Starter 

Hi tigon_ridge,

 

Thanks for pointing out such an interesting product.  It looks like something that might actually work.  beerchug.gif

 

I only hope that my posting here inspires people to start making their own electrostatic headphones.  Seeing you guys interested and actually make them makes me very happy.  bigsmile_face.gif

 

Wachara C.

post #529 of 1547

I'm almost done with my new headphone build, but I'm having what seems to be a very atypical resonance. Here's the FR:

 

Red - free air

Blue - no damping

Green - a few layers of felt on the back

 

 

So, what is that peak at 1khz? any idea? I've not had anything like this in previous builds I've done. The only thing I've really done is adding in two 1/4" ABS mounting plates as can be seen in the CAD drawing below (The black are ABS plastic 1/4" thick to support the PCB and make sure everything stays flat, the brown represents the driver). I have not yet installed a sweat screen.

 

 

 

 

 


Edited by dude_500 - 9/9/12 at 8:58am
post #530 of 1547
Thread Starter 

Very nice!  I have no idea where the 1khz peak is from, but have you tried listen to them?  

 

Wachara C.

post #531 of 1547
Quote:
Originally Posted by chinsettawong View Post

Very nice!  I have no idea where the 1khz peak is from, but have you tried listen to them?  

 

Wachara C.

I have, and the 1khz peak really destroys the sound. In a frequency scan 1khz is extremely noticable, and I can tell that range is way too present in music.

post #532 of 1547

This a very interesting thread, quite an original work. It might come in handy with my studies so I wouldn't like to see it disappear.

 

Does anyone know how to save the whole thread on my computer ?

post #533 of 1547

It appears there is a limit to bigger being better... the 1khz turns out to have been caused by my earpad inner cavity being too large. I tried out my old earpads, and it's pretty much flat again. You can see the difference between the two sizes below, as well as a frequency response for the smaller earpads. The driver is the same, just the earpad size is the difference:

 

 

 

 

post #534 of 1547

That's very interesting findings, dude_500!

 

Here's an interesting idea:

 

Have you guys thought about shaping the plate and/or earpad so that it concentrates the sound somewhat towards the ear canal? Not necessary anything drastic; maybe just a gentle slope towards the center. I think it would increase the phones' efficiency, to alleviate the need for a crazy-expensive electrostatic amp. I think it might also make the cans sound warmer (low frequency waves are easier to direct with soft padding material than higher frequencies?). Just a 2-cent.

post #535 of 1547
Quote:
Originally Posted by dude_500 View Post

It appears there is a limit to bigger being better... the 1khz turns out to have been caused by my earpad inner cavity being too large. I tried out my old earpads, and it's pretty much flat again. You can see the difference between the two sizes below, as well as a frequency response for the smaller earpads. The driver is the same, just the earpad size is the difference:

 

 

 

 

This sorta explains why Stax chose a more concentric shape for their flagships, while their affordable line-up has a more rectangular shape. The rectangular model is easier to construct; but in the end, the concentric design focuses lower frequencies towards the ear canal better, thus being warmer sounding than the rectangular models! I think I just had a eureka moment. It must be true that a concentric design allows for warmer sound. It explains why Chinsettawong's cans have the Omegas' warm sound! I feel smart. biggrin.gif


Edited by tigon_ridge - 9/9/12 at 1:27pm
post #536 of 1547
Thread Starter 

Hi Dude_500, 

 

Maybe your pads are too wide that they somehow obstruct or reflect the sound.  As for what I have experimented, I like thicker pads better.  They don't have to be that wide.  Thicker pads bring out a little more bass, and better comfort for wearing.

 

Wachara C.

post #537 of 1547

I know almost nothing about acoustic engineering, as I know many of us in this thread don't. Does anyone know what the theoretically ideal inner-edge of the earpad would be?

 

My new earpads that don't work well (1khz resonance) are approximately the red outline for inner-edge of the pad. My old pads which work well are approximately (but not quite) the green line.

 

Based purely on reasonless theorizing, perhaps the extra volume that is not in front of the driver has to be somehow filled with sound, and that filling can have resonance whereas if the inner area is entirely in front of driver, this filling effect doesn't occur. Building on that theory, I wonder if the yellow rectangle would be worse since it would cause some damping of the diaphragm, or possible even better than green since the very outer edge of the diaphragm probably doesn't actually move much compared to the center.

 

 

Anyone know if any of this is even remotely on with the science of the situation?

 

 

post #538 of 1547
Thread Starter 

I think it has more to do with the kind of material you use for making the pads.  Perhaps the leather is too stiff?  If you don't cover your pads with leather, would the result be the same?

 

Wachara C.

post #539 of 1547
Dude_500, I agree with wachara. You can estimate the first acoustic resonance in the earcup cavity assuming rigid walls but it doesn't line up. The frequency is such that half a wavelength fits across the largest dimension. So, in SI units: f0 = 340 / ( 2 * L ). At 1kHz, this corresponds to about 15cm and I don't believe you made that big an enclosure wink.gif. The pads are not rigid walls which shifts the first resonance frequency down (but hard to estimate by how unless one knows the foam elasticity). The other possibility is a resonance in the ear pad structure (affected by the foam you use and its dimensions). Where does the foam come from?
post #540 of 1547

The inner earpad area is 6.1x9.7cm. The foam is memory foam, with a density of 5.8 lbs./cu. ft. and and a softness classification of "very soft".

 

I remember trying it before I added leather and it still had a resonance around 1khz, although I neglected to save the plot so I don't know how the magnitude compares. I might be able to try it out later, but it was definitely still there and significant.

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