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Old 20th February 2012, 01:08 AM   #21
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Thanks ,Bolserst, The xls files help out a lot !!

I have a pretty good understanding but it hasn't completely sunk in yet as far as the two points in the curve is concerned.

I have read this over a few times in the Walker and Baxandal papers but I just don't have it as second nature yet,But I will in time.

The simulations do portray very close to what I had measured with my last little panel before it shorted out on me.
As I have done many measurements at various distances within 1 meter and less.

Only I had a few issues because they weren't done in a good free space and had lots of early reflections to decipher through.
But these were good for showing what is happening in a real world situation.

I still have those curves and I will dig them up to compare too and this will help me even more.

I was thinking that the little panel will act as a point source from a large distance but I never got that far to try it out,thus the need to build new panels.

I have a fresh memory of how the little panel sounded and it will be interesting to find out how a panel that is a little bit wider (50%) will act.

It is a little deceiving that the segmented ESL simulator does not take the lower frequency's into perspective, Although this is what I had expected as well.

jer
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Old 20th February 2012, 07:22 AM   #22
Calvin is offline Calvin  Germany
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Hi,

Stephen, with any change in the resonance and Q fields the response curve+Q vanishes.

jauu
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Old 20th February 2012, 01:38 PM   #23
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Quote:
Originally Posted by Calvin View Post
Hi,

Stephen, with any change in the resonance and Q fields the response curve+Q vanishes.

jauu
Calvin
Hmmmm...the resonance curve calculation does use complex variables.
Perhaps you don't have the Analysis ToolPak loaded in the Excel Add-Ins.

Which version of Excel are you using?
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Old 21st February 2012, 06:51 AM   #24
Calvin is offline Calvin  Germany
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2002
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Old 21st February 2012, 02:46 PM   #25
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Quote:
Originally Posted by Calvin View Post
2002
I believe with Excel 2002 you can activate the Analysis ToolPak by selecting Add-Ins from the Tools drop-down menu.
Then just check the Analysis ToolPak box and click OK. The spreadsheet calculations should start working.

If this doesn't solve your problem, or the Analysis ToolPak doesn't show up in your available list of Add-Ins, send me a PM or email and we'll figure it out off-thread.
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Old 21st February 2012, 03:38 PM   #26
Calvin is offline Calvin  Germany
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Hi,

yesterday I looked for the tools and the pc asked for installation CD, which I unfortunately donīt have at home, because itīs my companyīs pc.
Anyway, its a nice tool, but nothing Iīd desperately need at the time.
If it works on Your pc itīs totally ok.

jauu
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Old 11th March 2012, 10:12 PM   #27
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Default Segmented Wire Stator ESL Simulator (Q & A)

I've had quite a few questions sent to me concerning the segmented ESL simulator.
There were three that came up several times, so figured it might be worth posting them here.

Q1: "If the height entered for the line source doesn't change the calculated response since line source behavior is assumed, then why even have the option to enter a height?"

A1: "The height is still needed to determine the capacitance of each segment of the ESL panel. This capacitance directly affects the LP filter behavior calculated based on the ladder resistors you enter"


Q2: "How does this calculator compare to the AES paper on segmented ESLs and the simple sectioned line source Excel spreadsheet you posted here:"
experiences with ESL directivity?

A2: "All are in agreement"

Attachment 1: For comparison, let's take the example of a 20 segment ESL shown in Figure 9 of the AES paper. The solid line shows the simple model developed in the paper which is used in the Excel spreadsheet. The + symbols show the curve for the rigorous calculation of the segmented ESL using the same ladder resistor network as for the simple model.

Attachment 2: Using the segmented ESL simulator to model the same 20 segment ESL.

Attachment 3: Scaling Attachment 2 and overlaying with Attachment 1, you can see that the blue line is in good agreement with the curve of + symbols.


Q3: "Why does using the ladder resistor values from the AES simple model result in a +1dB bump just before the LF roll-off?"

A3: "As explained in the AES paper, the simple model assumes an infinite number of segments. Using a finite number results in an impedance miss-match at the end of the ladder-resistor RC line. If this concerns you, you can flatten the bump by terminating with some additional dummy load R-C sections as shown in Attachment 1. Alternatively, I have found that increasing the value of the ladder resistors for the last couple sections by about 50% gets the job done as well. Personally, I wouldn't lose any sleep over it."
Attached Images
File Type: gif ESL_SEG1.gif (24.9 KB, 197 views)
File Type: gif ESL_SEG2.gif (29.3 KB, 196 views)
File Type: gif ESL_SEG3.gif (40.5 KB, 200 views)
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Old 11th March 2012, 11:29 PM   #28
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Default Segmented Wire Stator ESL Simulator (Physical Build)

Somebody just reminded me I never posted the clarification I promised in post # 18 on what exactly the simulator is physically modeling.

I think the best way to do this is with an example...lets use the input parameters geraldfryjr selected in post #13.
Segmented Wire Stator ESL simulator (esl_seg_ui)

It was a 10 segment design with 2 wires entered for each section.
The segmentation resistors were: 180k,3.9M,5M,5M,5M,5M,5M,10M,10M,10M.

What the program is modeling is shown in the top figure of the attachment.
This is also how you would physically build and wire the segmented ESL stators.
Section #1 is the center section, made up of 2 wires with a capacitance of about 4pF. It is fed by the specified 180K ladder resistors.
Section #2 is made up of 2 wires to the left of section #1 AND 2 wires to the right of section #1. Both left and right portions of section #2 are fed from section #1 with the specified 3.9M ladder resistors.
Section #3 is made up of 2 wires to the left of the left portion of section #2 AND 2 wires to the right of the right portion of section #2. Both left and right portions of section #3 are fed from the adjacent portion of section#2 with the specified 5M ladder resistors.
etc...

To simplify modeling in SPICE, you can fold the left half of the ESL panel about the center section and combine the left and right portions of the outer sections in parallel as shown in the middle figure of the Attachment. The lower figure in the Attachment shows the resulting R and C values when the paralleled portions are combined.

Key point of possible confusion:
If you specify the same number of wires for each section in the entry block, what you are actually modeling is an ESL that has its first segment half the size of the remaining segments.
The lower figure in the Attachment makes this clear.
.
Attached Images
File Type: gif ESLbuild.gif (58.9 KB, 208 views)
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Old 12th March 2012, 07:41 AM   #29
Calvin is offline Calvin  Germany
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Hi,

is there a link to the AES paper?
The abovesimulation is of course a simulation. Therefore it should be taken with a grain of salt.
Two points:
a) The number of segments doesnīt need to be so large. Typically 2-3 electrical segmentations, i.e 3-5 mechanical segments are sufficient.
As a rule of thumb Iīd use max. 3 segmentations with the segment area increasing by a factor of 4 (2times doubling).
b) the capacitance values of each segment is very small. This means high impedance values, hence high transformation faktors of the audio tranny. practical values should be at least 10 times higher.
c) whats the purpose of the 180k resistors? If they are intended for damping HF resonace and to tune HF-response the value will in praxis probabely be lower. 360k as in the example already attenuates at 20kHz with -0,8dB.

jauu
Calvin
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Old 12th March 2012, 09:11 AM   #30
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Yes,I have had similar results using a lesser amount of segments.

In this configuration it was the flattest response and widest dispersion I could get for a first few go rounds.
As I haven't played with it much lately.

I have been waiting on the weather in order to start painting the stator pieces outside.

Yes ,the value of the 180k resistors effect the overall slope of the high frequencys in the simulations and their actual results I will find out when I get a sample built.

It almost seems to me that they may not even be needed as without them there is a boost at the high end of about atleast 2db without them.

I will have to play with the simulation again to verify the amount of this.

This makes the off center at 15 degrees or so the very flat range and this may most likely be better depending on what the angle of the panel is to the listeners position.

And may compensate for my slight hearing deficiency's at that end of the spectrum as well (he,he).

With my pattern on such a small panel it certainly points to the fact that only 3 or 4 sections are really necessary.
I will be able to experiment with this on the the panel as it will be built in such a manner to do so.


Cheers !!

jer
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