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Old 1st April 2007, 01:25 PM   #11
Paul W is offline Paul W  United States
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Calvin,
The foam may be slightly conductive to begin with. Can you check potential on the film itself?

I once tried a very thin, very open, random weave polyester from a fabric shop (like batting except very thin). It worked, but the film slapped against the weave which obviously sounded terrible. This was with a full-range signal, so something similar might work with a high-pass filter.
Paul
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Old 2nd April 2007, 06:30 PM   #12
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Default Have you considered...

fluid damping of the outer edge of the diaphragm? This could be done with ferro fluid and some magnets. For the sake of discussion lets assume that you take necessary measures to keep charge away from the fluid.
Another old idea I had from a couple of decades ago was to use an out of phase periferal strip of stators. Just wide enough to off set some of the diaphragm energy. Just throwing some additional ideas into the pot. Regards Moray James.
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Old 3rd April 2007, 04:07 PM   #13
Calvin is offline Calvin  Germany
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Hi,

btw. Your own personal thread doesn´t cost a dime here, You know??

I liked mine to keep to the foam-idea!

jauu
Calvin
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Old 4th April 2007, 12:57 AM   #14
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Default sure be calm...

just inserting some ideas that I honesly thought might interest you. You could try contacting Bill Perkins at pearl-hifi.com. Bill used open cell foam of the thickness you are interested in for the surround of his tweeter. I have called Bill but not had any response regarding this. So in the intrim I figured I would suggest some different ideas just to add some fule to the fire. Hope Bill can be of some assistance. In the mean time...
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Old 8th April 2007, 02:57 PM   #15
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Calvin,

By all means go ahead and experiment.

My brief foray into the rebuild of the Stanton Isophase did not have very excellent results.

If you expect the foam to be linear, like air, it is not.
Foam is much much stiffer than air.
If you expect to be able to have large excursions, you can't.
It might fly for an ESL HF section...
The main benefit is that you can curve it in theory.

I found controlling the foam's shape was non trivial.
Also preventing compression of the foam and still mounting it was non-trivial.

Plus foam likes to disintegrate in the presence of O3, unless perhaps you find some specialized foam material in the required thinness...

A difficult thing to master, imho.

keep us posted!



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Old 9th April 2007, 09:58 AM   #16
Calvin is offline Calvin  Germany
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Hi,

depending on the shore value of the foam up to 50% of compression should be possible with acceptable linearity. Still though the stiffness could be too high to get conssiderably lower than ~1kHz, but it might be possible to use foam with a hole pattern in it -thinking of kind of a net structure (using quadratic holeshapes of less than 10mm sidelength). This would yield numerous very small and freely vibrating membrane segments and lots of soft supporting points.

A very serious point is O3 stability. Thanks, I´ll have to check on that!
Great Input from Your´s :-)

jauu
Calvin

ps. couldn´t find any useful material about the Stanton Isophase yet, but I´ll keep on
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Old 15th April 2007, 02:58 PM   #17
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JAES Speaker Anthology Vol I.
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Old 15th April 2007, 07:20 PM   #18
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Default From memory...

I think that Bill used a combination of siliconized Latex sealent (water based) mixed with India ink (to block UV) diluted with water. The foam was saturated in the solution then squeezed dry and left to dry. This means that you probably want to start with a lighter density foam as the sealant will stiffen it up some. You might also consider replacing the India Ink with a high SPF sun screen. You can expect a foam like this to last 10 - 15 years in use depending upon local conditions. There are a number of Bill's tweeters still functioning well that are older that this. Have fun. Regards.
PS: I would guess that current day production foams are superior to those made 20 years ago. All depends upon the intended application and exposure. Thin foams of the type you are looking for are commonly used as padded backings for vinyl films used to make them have a nice surface feel as on note book covers etc..
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Old 16th April 2007, 09:30 AM   #19
Calvin is offline Calvin  Germany
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Hi,

I appreciate Your support very much, but some of it is really not understandable. You should realize that especially abbreviations that might be common in Your part of the world are not in a different part of the world.

e.g SPF! "Now introducing....S(uper)P)ower)F(orce) the new super hero team of Marvel comics"?
And who is Bill? Kill Bill´s Bill? Billy the Kid? Or a Dollar Bill?
Qs after Qs!

jauuu
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Old 16th April 2007, 12:44 PM   #20
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