Large Coil Simulation Accuracy Issue and Adjustment - diyAudio
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Old 24th August 2015, 03:09 PM   #1
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Default Large Coil Simulation Accuracy Issue and Adjustment

Without adjustment, Hornresp and other programs don't accurately simulate drivers with very large voice coils. With a minor adjustment most of the variation can be eliminated.

Previously thought to be an issue caused by high inductance, it is now suggested that high inductance and simulation inaccuracy are both symptoms of this larger issue of very large voice coils.

This adjustment is now included in the newest version of Hornresp, just check the "Large Voice Coil" checkbox and the adjustment is made automatically. There's also a formula you can use in other simulators if you don't use Hornresp.

There's also a paper that I wrote on the issue, how to tell which drivers are affected, a description of the process leading up to the formulation of the new adjustment method, and 30 examples of unadjusted and adjusted sims compared to real professional measurements. The sample size is 22 drivers, some measured in multiple enclosures. The simulation accuracy of the new adjustment method is very good, even better than the original method.

This is the link to the download page for the paper - https://sites.google.com/site/amateu...and-adjustment

It's a long paper but it's mostly pictures, it doesn't take long to read.

Special thanks to the contributors, LTD02, David McBean and Josh Ricci.

I can answer any questions on this topic but I have no internet at home at this time. I'll try to get online once a day if I can.

Click the image to open in full size.

Image courtesy of LTD02.

Last edited by just a guy; 24th August 2015 at 03:14 PM.
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Old 24th August 2015, 10:31 PM   #2
Zero D is online now Zero D  United Kingdom
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Fame @ last

Could you please upload the PDF here
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Old 24th August 2015, 11:00 PM   #3
bamfwrx is offline bamfwrx  United States
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this is great thanks
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Old 25th August 2015, 01:37 AM   #4
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Quote:
Originally Posted by Zero D View Post
Fame @ last

Could you please upload the PDF here
Unfortunately no. This forum won't accept pdf attachments larger than 997 Mb, I don't think any forum will. I really didn't want to host it on that old website but that was my only choice.

Looks like my modem is working tonight, fingers crossed it has decided not to be broken anymore.
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Old 25th August 2015, 03:28 AM   #5
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Try https://www.pdfcompress.com/

I've used it with great success before. Might get it under the 1mb mark.

Edit: Just tried it myself. No luck. :/

Last edited by zettairyouiki; 25th August 2015 at 03:30 AM.
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Old 25th August 2015, 08:23 AM   #6
Zero D is online now Zero D  United Kingdom
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@ just a guy

Thanx, got it. The reason i couldn't before, was due to my locking down my normal browser in various ways & methods, for security & privacy reasons. I used a different version that i have for other things, as & when = not often !

I offer some initial observations & input.

Figure 12 - Scatter chart - Linear & Logarithmic trendline look the same, even though the formula details are different ?

In all the graphs, the upper frequency variations/spikes, appear in the same, or almost the same positions ! So this technique only seems to affect the lower f's = good.

It's most likely that some of the larger voicecoils heat up more than others, even with the same/similar power. Which means that the magnets do too. Magnets lose strength when heated, especially Neo ones ! Whether this is significant or not ?

The combination of increased Re & lower BL due to increased heating, = bingo.

It "might" be possible to gain more insight ec, if we could get the Equivalent Circuit for each driver/design ! For eg, see my screenie from WinISD's helpfile for a vented. I'm not sure if any for TH's have been published though ?

Having said that, simulators must sim these parameters in order to work. So for eg, HR could possibly display these numbers with the symbols in a seperate window. And "maybe" we could interactively change these, or the relevent ones related to this subject. If so, we could see the changes graphically. It "might" then be possible for eg, HR to automatically account for & show this ?
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Old 25th August 2015, 02:16 PM   #7
tb46 is offline tb46  United States
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Hi just a guy,

"Thank You" for the effort. It is highly appreciated.

Regards,
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Old 25th August 2015, 02:20 PM   #8
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Originally Posted by Zero D View Post
Figure 12 - Scatter chart - Linear & Logarithmic trendline look the same, even though the formula details are different ?
They look quite different to me, one looks like a straight line and the other looks like a hockey stick shape. And the curved line gets a lot closer to the drivers on the left side of the chart whereas the straight line doesn't get too close to them. The formula is different because the lines are different.

If you mean the curved line doesn't seem to fit the data better than the straight line, it actually does. Looking at the percentage each driver is off the line the curved line has less percentage of variance.

Quote:
It's most likely that some of the larger voicecoils heat up more than others, even with the same/similar power. Which means that the magnets do too. Magnets lose strength when heated, especially Neo ones ! Whether this is significant or not ?
Actually larger voice coils will have a lot more copper (or aluminum) and a lot more surface area and sometimes even larger wire (smaller gauge) so they should heat up much slower than smaller voice coils.

Quote:
It "might" be possible to gain more insight ec, if we could get the Equivalent Circuit for each driver/design ! For eg, see my screenie from WinISD's helpfile for a vented. I'm not sure if any for TH's have been published though ?

Having said that, simulators must sim these parameters in order to work. So for eg, HR could possibly display these numbers with the symbols in a seperate window. And "maybe" we could interactively change these, or the relevent ones related to this subject. If so, we could see the changes graphically. It "might" then be possible for eg, HR to automatically account for & show this ?
Any extra info on the voice coils would be a good thing but I'm not sure what you would do with an equivalent circuit. The adjustment method works quite well as it is, it's already automatically done in Hornresp and it's just a single parameter that is adjusted. I'm not saying the method can't be improved but it's already quite simple and very accurate as it is.

I do appreciate your interest but I'm not sure what we could really do with an equivalent circuit and I'm not sure it would be very easy to improve the existing method.
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Old 25th August 2015, 02:26 PM   #9
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Quote:
Originally Posted by bamfwrx View Post
this is great thanks
Quote:
Originally Posted by tb46 View Post
Hi just a guy,

"Thank You" for the effort. It is highly appreciated.

Regards,
No problem guys, I needed to do it anyway and I like to share. The reason I didn't do this a long time ago was because I knew it was going to be a lot of work. The original generic method took literally no time to develop, I just tried something that seemed like it might work and it worked. This time around I spent about 100 hours developing the new adjustment method and writing it up. I think it's well worth the time spent when looking at the accuracy of the sims in the 30 examples. The image in post 1 was pretty shocking too when LTD02 sent it to me, I hadn't seen an actual overlay before and I was surprised the adjusted curve shape matched so well. Sensitivity is off, but there was no input voltage specified for that particular measurement anyway (I think Ricci blew that driver up before he got all his testing done), and LTD02 just wanted to show the curve shape matched really well.
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Old 25th August 2015, 02:56 PM   #10
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Excellent work just a guy!
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