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Old 6th February 2013, 08:08 AM   #21
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When playing very loud, the es200 with mirror drive will compress the lowest bass and driven harder, it will distort. It is a compromise between bass extension and power. It's no free lunch.
That's one of the reasons I am working on a hybrid design......
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Old 11th February 2013, 12:25 PM   #22
AAaF is offline AAaF  Norway
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Quote:
Originally Posted by bolserst View Post
A segmented panel does not connect all of the panel area directly to the transformer. Rather it uses resistors to segment the panel area so only a small area is directly driven by the transformer at high frequencies(HF). This is important because the panel capacitance will limit the HF bandwidth due to an underdamped low-pass filter formed with the transformer leakage inductance. The Audiostatics are 2 segment designs.

The minimum Z point indicates the frequency where the response of the transformer will start to roll off.
In general you would like this to be >20Khz, but even 15kHz is useable.

For example:
Attachment #1: shows a model for the impedance and transformer response for Audiostatic ES-100. The resonance between transformer leakage inductance(LL) and panel capacitance can be seen by the minimum dip in impedance at 13,669Hz. You can see that this corresponds with the roll off point of the HF response of the transformer.

Attachment #2: shows what would happen if the whole panel was hooked up to the transformer without segmentation.
Resonance is moved down to 7,671Hz as is the HF roll off point.

Attachment #3: using the model we can compare the response for different values of resistors and capacitors in the primary circuit. You can see that the transformer response changes match pretty well the differences you measured.

In general, increased resistance dampens the resonance and rolls off the response. Adding a capacitor in parallel with the resistor can help to reduce the roll off or peak the response above the resonance point when a larger resistance value is used.

If anybody would like to play around with the modeling tool, let me know and I can post the Excel spreadsheet.
Excellent folks, thank you very much!

@esltransformer: Is it possible to get an uprated transformer? As far as I can see, it's used plated transformers, is it uncommon to use ferrite core? I'd think this would possibly improve HF response...? Pardon any ignorance, transformers are not my specialty...
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Old 11th February 2013, 05:29 PM   #23
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Originally Posted by AAaF View Post
Excellent folks, thank you very much!

@esltransformer: Is it possible to get an uprated transformer? As far as I can see, it's used plated transformers, is it uncommon to use ferrite core? I'd think this would possibly improve HF response...? Pardon any ignorance, transformers are not my specialty...

A transformer as I made for myself is not a real "upgrade" for a Audiostatic.
My transformer is much better then the original AS so it's not plug&play. You have to change the segmentation, less wires for the middle section and maybe different resistors too. Also the serieresistor should be changed in a much lower value.

Ferrites are not suitable for audio frequencies, the benefits for ferrite is for f>100kHz
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Old 22nd February 2013, 02:52 PM   #24
Bazukaz is offline Bazukaz  Lithuania
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What material audiostatic horizontal strips which support wires are made of ?
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Old 22nd February 2013, 03:10 PM   #25
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What material audiostatic horizontal strips which support wires are made of ?
The Audiostatic horizontal supports are made from aluminum. In my experience, it is not desireable to use metal for wire supports when building segmented stators. The reason is that there will be capacitive coupling from segment to segment throught the metal supports that bypass the segmentation resistors. So, high frequencies are not filtered out from the segments further from the center of the panel like you might think just looking at the schematic. Dispersion suffers compared to a panel made with non-conductive wire supports.
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Old 22nd February 2013, 04:38 PM   #26
Bazukaz is offline Bazukaz  Lithuania
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Quote:
Originally Posted by bolserst View Post
The Audiostatic horizontal supports are made from aluminum. In my experience, it is not desireable to use metal for wire supports when building segmented stators. The reason is that there will be capacitive coupling from segment to segment throught the metal supports that bypass the segmentation resistors. So, high frequencies are not filtered out from the segments further from the center of the panel like you might think just looking at the schematic. Dispersion suffers compared to a panel made with non-conductive wire supports.
Thanks. I suspected that it's from aluminium from some pictures.
It's quite strange why they used such a material. I have not thought about capacitive coupling causing segmentation resistors be bypassed . IMO it's not the safest way to build stators as there is still a possibility of wire insulation breakdowns or even mechanical damage.

Lukas.

Last edited by Bazukaz; 22nd February 2013 at 04:40 PM. Reason: extend
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Old 22nd February 2013, 07:05 PM   #27
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Originally Posted by Bazukaz View Post
Thanks. I suspected that it's from aluminium from some pictures.
It's quite strange why they used such a material.
It probably comes down to trade-offs between (structural stiffness vs size) and (material cost vs labor cost).

Aluminum(6061) is 10 - 20 times stiffer than plastics of same size so you can build thinner stator frames with aluminum.
This would be especially important when the cross bars need to span 30cm wide panels like the ES-500.
Also, Aluminum is stable where as most plastics can/do warp over time.

Aluminum may cost more, but it can be purchased in various stock shapes/sizes that can be used as is without any additional labor.
Use of plastics usually involves the need to cut smooth, straight cross bars to size from sheets of material.
This may not be important for DIY, but could be driving factor for a manufacturer.

Last edited by bolserst; 22nd February 2013 at 07:16 PM.
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Old 22nd February 2013, 11:25 PM   #28
Bazukaz is offline Bazukaz  Lithuania
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Well I think optics was perhaps a factor to use aluminum.
Currently I am not a big fan of open stators mainly due to attraction of dust.
Have been fighting to make the speakers free of buzzing noises while doing sine sweeps for months and it looks like I am finally getting acceptable results. But that includes some protection of dust, at least a light, semi-transparent synthetic cloth.

Regards,
Lukas.
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Old 24th February 2013, 05:13 AM   #29
Calvin is offline Calvin  Germany
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Hi,

after my experience with aluminum frames like Audiostatic (pics of those on my website) the capacitive coupling doesn't play any significant role here.
If You want to design a 'open' stator, the redish card board often used for the inner frame structure is out. Some black plastics or transparent acrylics may be left. But those materials may have stability and strength and fixing issues. The aluminum bars are standard off of the shelf products available in any DIY store here in Germany either as square hollow tube or massive rod or in rectangular shapes. They have a good looking anodized surface, are stiff enough even for wide panels, can be easily sourced and glued. One needs to watch if the glue is agressive to the wire insulation which over time could result in leakage or even breakdown. Plastic bars may not stick well with non-aggressive glues. With aluminum bars one may even use simple waterbased household glues to fix the wires. A cheap, easy to use and reliable solution ... and very DIY
I've used hollow square of 10x10mm shape and massive 2x10mm shape in several panels successfully.
Panels are working well even after 20 years. So far the only thing I noticed every now and then is, that the metal bars aquire a bit of charge over time, that faintly zapps you on touching them. But the zap is even less than what happens walking over a carpet.

jauu
Calvin
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Old 25th February 2013, 03:25 PM   #30
Bazukaz is offline Bazukaz  Lithuania
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Hi,

Perhaps it depends a lot on specific implementation.
Here is some calculations I have carried out by using various calculators :

Assumptions :
1) Supporting strip is 10x10mm
2) Count of supporting strips : 20 per stator
3) Wire diameter 2mm, PVC insulatation thichness 0.6 mm.
Assume a simplification : this acts like 1mm wide conductor, 0.6mm insulator, k(PVC) = 4.
4) Wire sections : 24+12+6+12+24

It turns out that each wire can have about 0.6 pF capacitance to one supporting strip(simplification, but perhaps conservative due to assumptions in 3).

a) Reactance from center wires to supports. Multiply this by number of strips x number of wires and we have a summed capacitance of center segment to all strips :
0.6x6x20 ~= 72 pF.
b) Reactance from next segments to supports uses two times more wires(x2 segments) therefore it's capacitance is 72x2x2 = 288pF.
c) By calculating series capacitance, we have the result.
The first segmentation resistors are bypassed by equivalent capacitance of about 57.6 pF.
The 2-3 segments are bypassed by far larger capacitance of about 230 pF.

It turns out that under these assumptions segmentation resistors are bypassed with significant capacitance which can have even lower reactance than resistance of resistors.

Regards,
Lukas.




Quote:
Originally Posted by Calvin View Post
Hi,

after my experience with aluminum frames like Audiostatic (pics of those on my website) the capacitive coupling doesn't play any significant role here.
If You want to design a 'open' stator, the redish card board often used for the inner frame structure is out. Some black plastics or transparent acrylics may be left. But those materials may have stability and strength and fixing issues. The aluminum bars are standard off of the shelf products available in any DIY store here in Germany either as square hollow tube or massive rod or in rectangular shapes. They have a good looking anodized surface, are stiff enough even for wide panels, can be easily sourced and glued. One needs to watch if the glue is agressive to the wire insulation which over time could result in leakage or even breakdown. Plastic bars may not stick well with non-aggressive glues. With aluminum bars one may even use simple waterbased household glues to fix the wires. A cheap, easy to use and reliable solution ... and very DIY
I've used hollow square of 10x10mm shape and massive 2x10mm shape in several panels successfully.
Panels are working well even after 20 years. So far the only thing I noticed every now and then is, that the metal bars aquire a bit of charge over time, that faintly zapps you on touching them. But the zap is even less than what happens walking over a carpet.

jauu
Calvin
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