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Old 12th December 2008, 04:04 PM   #11
SM7UYJ is offline SM7UYJ  Sweden
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Ok - have just finished painting a couple of new test stators!

They are 350 x 1000 x 1.5 mm

This time I'm going to try my 4.8m film and 1.5mm spacing.

Is there any gain in splitting the area into a "tweeter cell" of abt. 20-30mm along the side and the rest off the area into cells off abt. 125x300mm ?

/R
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Old 12th December 2008, 04:49 PM   #12
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Yes a tweeter cell will give you benefit, especially if the stator is electrically separated from the rest. Then you can start playing with attenuation resistors in series with the stators (of the big section).

It's hard to tell from the picture, but how open is your stator material? It looks like it may be a little bit too open.
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Old 12th December 2008, 05:03 PM   #13
SM7UYJ is offline SM7UYJ  Sweden
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The stators are 5mm holes, separated 8mm.

Here is a picture off a previous testpanel in the same material:

Click the image to open in full size.

The new testpanels have smaller holes - will post a picture when they are up and running!

/R
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Old 12th December 2008, 05:14 PM   #14
Calvin is offline Calvin  Germany
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Hi,

I disagree with arend-jan about best tension values. To my taste and experience the best value is always the highest possible, just before the membrane material starts to flow.
For the few usable membrane materials this means a elongation of typically 1-2%. Above this value the material starts to flow. The resonance freq wont rise any more.
Since ESL panels are normaly used in open baffle montage, there is no sense in trying to reach a very low crossover-frequency, hence a very low fo. Instead its better to place the crossover-freq not lower than a point where a max. equing of ~6dB is needed. Even with a 40cm wide panel this point is reached around 200Hz. Stretching a 4.8m film to 1-2% elongation will result in a fo of ~120-150Hz (with properly distanced spacers). A d/s is 1mm should already be ok, but with a certain safety headroom to cope with uneven stators and acoustic coupling 1.5mm is fine.

jauu
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Old 13th December 2008, 09:36 AM   #15
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Hi Calvin,

technically I don't think we disagree that much. You just take a different design approach. Once you allow your resonance frequency to be high by design, of course maximum tension is preferred.
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Old 13th December 2008, 10:48 AM   #16
SM7UYJ is offline SM7UYJ  Sweden
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New panel now playing!

Click the image to open in full size.

Painted 1.5mm alusheet 3mm holes, spacers 1.5mm tape, 4.8m Hostaphan, MTAudio coating.

Sounds realy good - have not measured frequency response yet, but they seem to have better highs than previous.

Divided the area into 6 cells as my first try ended with the tape slipping when i atached the film!

(stuck to the film very good, but not to the paint om the stators)

First tensioned to 2.5kg/10cm but reduced to 2kg/10cm and the tape now sticks to stators good.
I also have the panel "under preasure" from the wooden frame slots.

Time will tell if it holds, and if it does, I'm going to have some of this aluminum anodized.

/R
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Old 13th December 2008, 11:32 AM   #17
Calvin is offline Calvin  Germany
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Hi,

fine What do You expect to get by anodizing the aluminium?
To insulate properly only a thick layer of laquer is the way to go.

jauu
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Old 13th December 2008, 05:53 PM   #18
SM7UYJ is offline SM7UYJ  Sweden
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I anodize for mainly two reasons:

1. Durability - scratch resistant, no problems with chemicals if I want to desolve glue etc.

2. Esthetics - looks good as color is even and it gets in everywhere.

The oxide is very thin, so I do'nt know if the insulation it provides is of any use with these high voltages?

The panel with the painted stators sound realy nice, so I think I'm going to bild a more permanent frame for them.

Have a 10" woofer on the shelf in the garage, that perhaps could be a mate for a complete speaker!?

/R
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Old 14th December 2008, 08:53 AM   #19
Calvin is offline Calvin  Germany
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Hi,

the thickness of the oxide layer is typically ~25m, which is by far too less to have any remarkable insulative effect. Dont ever touch Your panels when playing music! Could be the last thing You did!
Expect to need a insulator thickness of ~0.5mm for the high voltage levels of Your design if You dont have the the metal sheets thoroughly deburred and ~0.3mm with well deburred sheets (rounded hole edges). You could use a standard clear PU-laquer and spray the panel at least 4 times each side. This is a very durable and scratch resistent material used as coating for staircases or boats. Its electrical values are very suitable as ESL coating.
Since Your panels dont look optimally designed yet, You might do this with the next panels and think about curving the panels
Click the image to open in full size.
see the nicely rounded hole edges, which btw. increase the bandwidth of the system.

jauu
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Old 14th December 2008, 12:11 PM   #20
SM7UYJ is offline SM7UYJ  Sweden
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Quote:
Since Your panels dont look optimally designed yet, .....
Hrmpf......I'm deeply offended!

The eternal "problem" with DIY - You always come up with a better version along the way => never ending story!

How did you round the edges Calvin - etching?

Curved stators is a project for the future, have enough factors to sort out with my flat ones!

I have measured the current test panels and have a relativly flat frequency response from 100Hz to ~7kHz where they start to fall off.

Project for the wekk will be to paint a couple of tweeter stators in the same material.

/R
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