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Orthodynamic Roundup - Page 1428

post #21406 of 23377

I'm confused about this mylar... isn't that basically like making it closed on the back?

post #21407 of 23377

The idea is to keep the mylar disc loose so it moves in tune to the sound rather than blocking it.

post #21408 of 23377

Though as a non-permeable material it must still reflect. 

 

I wonder if sandwiched between some very soft material and not compressing it would work as well, rather than trying to blu-tack it. 

post #21409 of 23377

It's not completely transparent, that's for sure. Almost, though.

 

I'm not sure what happens if you sandwich it. Might have created a reflex disc then.

post #21410 of 23377

As long as the sandwiching material isn't constraining it, it probably wouldn't be any more of a reflex disc than it already is.

post #21411 of 23377

I'm not sure I fully understand what you mean by sandwiching in this case. The way I pictured it was to have round discs between which you put the disc of mylar, i.e. the mylar's surface is fully covered by the other two discs.

 

In any case, I tried crumpled mylar (Stax style, though not quite as elegant) on the other driver.

 

 

 

 

 

Black in the above graph is with the crumpled mylar, grey is without. Note that I forgot to measure the response on that channel before I modded it, so the grey line is from an earlier measurement (perhaps with slightly different mods inside the cup).

 

Much the same treble effect as with the smooth mylar disc: extra energy around 4-5 kHz. Here, though, the 700 Hz wonkiness is stronger, and there's an extra derp before 1 kHz.

 

 

 

 

 

The first CSD plot is without mylar, second is with. Here it's apparent that the crumpled mylar seems to have caused ringing at 700 Hz, as did the smooth version. Very clear ringing on the 1 kHz dip, too.

 

So the crumpled mylar seems to not be quite as good as the smooth one. I had the same result on the Unipolar - smooth mylar was more acoustically transparent than crumpled. I know Stax likes to crumple theirs, so I may do something wrong. Maybe it's the thickness of the mylar.


Edited by vid - 4/8/13 at 5:26pm
post #21412 of 23377
Quote:
Originally Posted by vid View Post

The idea is to keep the mylar disc loose so it moves in tune to the sound rather than blocking it.


A) Ok I am confused here as well. What exactly is the experiment supposed to accomplish? Moving in tune seems to be some kind of leaky isobaric thing and I cannot see that as good. (in fact the ringing that seems to appear would seem almost inevitable)

 

B) Are you shure stax uses crinkled and not patterned mylar?

post #21413 of 23377

It's a dust guard, keep out dust etc. but let the sound pass.

 

From what Stax has stated, they hand-crinkle their dust guards. All I know.

post #21414 of 23377
Quote:
Originally Posted by vid View Post

It's a dust guard, keep out dust etc. but let the sound pass.

 

From what Stax has stated, they hand-crinkle their dust guards. All I know.


Ah. Don't know if I would bother with mylar, regardless of stax' apparent endorsement.

post #21415 of 23377

Stax may use some other material. I think Sennheiser used mylar.

 

This was the effect of a DIY mylar dust guard on the Unipolar. Frequency responses reflect relative changes rather than absolute values.

 

 

Blue line is with no moisture guard. Pink line is with smooth mylar. Orange is with crinkled mylar.

 

Smooth mylar was largely transparent acoustically - you'll find a disc of thin foam less so. As a bonus, the mylar was and is impervious to dust, hair, moisture, etc.


Edited by vid - 4/8/13 at 5:26pm
post #21416 of 23377

By sandwiching, I meant placed between two other discs of material. But very lightly so they don't cause too much compression (and thus more rigid, which would make them less transparent).

 

In any event, the only way they'd be transparent were if it were extremely thin and light such that energy is transferred almost completely through with minimal reflection (I believe this requires that it have the same acoustic impedance, though I'm not sure how one would calculate the acoustic impedance through a thin film... the bulk calculation is simple though). A thicker mylar will reflect more than not, and a crinkled one will actually become stiffer and reflect more as well. 

post #21417 of 23377

I think to make the mylar more rigid is actually the goal in crinkling it. I also think that rather than theorizing about it you should do experiments and see what happens.

post #21418 of 23377
Quote:
Originally Posted by vid View Post

I think to make the mylar more rigid is actually the goal in crinkling it. I also think that rather than theorizing about it you should do experiments and see what happens.

 

Bizzare little hump from 300 to 700 you have there.

 

i would think crinkling is more to make the mylar diffuse than to harden it (theory)

post #21419 of 23377

http://www.head-fi.org/t/223263/the-stax-thread-new/19110#post_8601756

 

Stax's procedure outlined there. They are quoted saying crinkling is to reduce resonances. No further info.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8629606

 

One guy's guess as to Stax's material. He apparently finds mylar a good substitute in any case. Note the 'no tension' bit.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/495#post_8643618

http://cdn.head-fi.org/e/ea/eaf088ce_DSC00274.jpeg

 

AT + Stax guards. Crinkled but only slightly. Could be that I'm making my crinkles too large, and indeed could be that thinner material is needed for crinkling to work.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8633529

 

Some guy's DIY crinkled guards + measurements. Transparent, though I question the 1.5 kHz derp. He guesses the crinkling is for structural rigidity. Loose tensioning.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8630721

 

Sony's guards. The poster says they have crinkles, but kinda hard to go along with him on that from the pictures. Note again the 'low tension' plea.


Edited by vid - 4/6/13 at 6:58am
post #21420 of 23377
Quote:
Originally Posted by vid View Post

http://www.head-fi.org/t/223263/the-stax-thread-new/19110#post_8601756

 

Stax's procedure outlined there. They are quoted saying crinkling is to reduce resonances. No further info.

 

This implies Diffusion .

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8629606

 

One guy's guess as to Stax's material. He apparently finds mylar a good substitute in any case. Note the 'no tension' bit.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/495#post_8643618

http://cdn.head-fi.org/e/ea/eaf088ce_DSC00274.jpeg

 

AT + Stax guards. Crinkled but only slightly. Could be that I'm making my crinkles too large, and indeed could be that thinner material is needed for crinkling to work.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8633529

 

Some guy's DIY crinkled guards + measurements. Transparent, though I question the 1.5 kHz derp. He guesses the crinkling is for structural rigidity. Loose tensioning.

 

He guessed wrong.

 

http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/480#post_8630721

 

Sony's guards. The poster says they have crinkles, but kinda hard to go along with him on that from the pictures. Note again the 'low tension' plea.

 

I can see using the surgical mesh on the Sony's (I suspect that's a polypropelene). However before I went down the road with mylar I would want to mic it in an anechoic box and see the results.

 

 As you are aware there is a lot more going on in an electrostat than an ortho  and frankly with all the materials available there have to be better solutions than mylar. The work/reward ratio on this seems way out of proportion.

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