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Old 15th March 2007, 07:27 AM   #1
Calvin is offline Calvin  Germany
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Default search for very thin (open pores) foam layers

Hi,

I´m searching for very thin layers of Polyurethane-foam with open pores(!)

Thicknes: ~1mm (1/25inch)
Pores: 50-100PPI
Material: Polyurethane preferred, Polyethylene possible

My inquieries up til now lead to the resut, that companies cutting a layer from a solid block of foam will sell at minimum 2mm thickness

Does anyone have infos about a source providing the very thin stuff?

Thanks
Calvin
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Old 17th March 2007, 10:47 PM   #2
BillH is offline BillH  United States
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Hi, Calvin. MCM Electronics has two sizes of 1mm foam listed as speaker grilles. The material type is not listed, but I assume from its intended use that it is open cell. 31" x 17" and 26" x 23". How much foam do you need?
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Old 20th March 2007, 12:03 PM   #3
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Hi Calvin,

the only i found is www.modulor.de

They have very open foams but lowest thickness is 3mm.

I guess you want to put the foam in between the membrane and the stator to damp the fundemental and other resonances.

I tried that on a 3mm distant stator-membrane ESL with the foam described above. Works in principle but depending on the losses of the foam material field densitiy in the air gap is significantly compromised.

Capaciti
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Old 20th March 2007, 06:56 PM   #4
Calvin is offline Calvin  Germany
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Hi Großer ,-)

habe mal mit 2mm und kleiner Fläche (Europakarte) versucht, jedoch keinen nennenswerten Pegel erzielen können. Allerdings sind F-gang und Step besser als mit Luft-Dielektrikum. Die Grundreso fehlt völlig, dafür ein sauberer Anstieg/Abfall. Mit Schaum müssten sich eigentlich eine markante Vorteile ergeben. Ich weiss aber im Augenblik noch nicht, wo die Verluste herkommen sollen, die Du erwähnst. Mit epsilon deutlich unter 2 und Verlustwinkeln unter 0,05 sollten die Pegel eines Luftdielektrikums ebenfalls erreicht werden??!!
Habe jetzt eine Quelle entdeckt für offenporigen Silikonschaum bis unter 1mm Stärke.
Werde das weiterhin versuchen, weil die theorischen Vorteile beträchtlich wären.

Gruss
Calvin

ps: Deine ´blaue´ Beschichtung läuft gut und stabil ;-)
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Old 26th March 2007, 04:57 PM   #5
Lucius is offline Lucius  United States
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Perhaps here...

http://www.tchfoam.com/
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Old 27th March 2007, 08:00 AM   #6
Calvin is offline Calvin  Germany
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Hi,

I found a source. They ´cast´ the foam on a film down to 1/32" thickness.
Have to figure out now if it is possible to get the stuff on a thinner film (maybe my own ESL-diaphragm) or without the film at all.

Thanks for the help to all of You ;-)

Calvin
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Old 31st March 2007, 02:43 PM   #7
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Calvin,

In case you might think that the open cell ESL construction is something new or unique - check the Stanton Isophase ESL!

I found one.
The foam was dead.
Rebuilt it with new foam.
Had similar issues finding thin foam.
Found that the foam impedes good bass reproduction.

Not so great across the range either...

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Old 31st March 2007, 04:38 PM   #8
Calvin is offline Calvin  Germany
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Hi,

You´re right As with most points regarding ESLs, nearly everything has been said or done sometime by somebody already before.
Still though, if You plan on a panel for a hybrid ESL the usage of thin foam has some distinct advantages in theory, I´d like to proove in praxis. Higher efficiency, no ground resonance (You can design the freqency range and behaviour by the ´parameters´ of the used foam), less problems with standing wave effects --> lower distortion, translatory movement of diaphragm instead of bowing, improved dynamic headroom and easier to build and longer lasting since You wouldn´t need to take care much of diaphragm tension.
It almost sounds to good to be true, doesn´t it? And thats why I want to try out where the pitfalls lie ;-)

jauu
Calvin
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Old 31st March 2007, 09:52 PM   #9
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Hi,

Wouldn''t the foam get dirty and conductive over time?
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Old 1st April 2007, 07:36 AM   #10
Calvin is offline Calvin  Germany
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Hi,

the danger of developing leakages over time is there, alright, but so it is with any other ESL too. The foam can be treated, such that it has hydrophobic quality.
I´d like to know if anyone has made some positive or negative experiences with foam yet.
My first test showed excellent results apart from efficiency, which was exceptionally bad. Anyone suggestions what might be the prob (field density, field strength?)

jauu
Calvin
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