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I've taken some measurements of one of my Infinity 1260ws and didn't really want to throw it in the HzHorn thread, even as gracious as BTH is. If you want the backstory, read posts 224 through 330 in that thread: http://www.avsforum.com/forum/155-diy-speakers-subs/1908857-hzhorn-8.html#post33235473 The TLDR would be: diy speaker guy realized that higher-inductance drivers, when measured, don't match the performance predicted in their models. The real issue is that most modeling apps like WinISD or even HornResp don't use a detailed inductance model. dsg found a way to get more accurate results by adjusting Re and Power, and LTD02 countered by suggesting we adjust Bl, Qes/Qts, and Le. Tweaking the TS params in this way gets modeled results much closer to the measured ones.

With that said, I've got measurements of an Infinity 1260w to share.

Here's my FR and Impedance sweeps and the calculated TS parameters. FR sweeps are close-mic'd at about 1/2" with a UMIK-1. Measured Qtc of the driver in the empty, sealed 38.6L box is .977.





Now, here's the WinISD models. All are in a 38.6L box, Qa=100, Ql=50.
The green line is Infinity's published TS parameters. Qtc of the driver in the enclosure was 0.7.
The blue line is based on my measured TS parameters. Qtc of 0.892.
The purple line is my measured parameters with BL adjusted to 14.5, Le to 6.5 mH, and letting WinISD recalculate Qes at .686 and Qts at .619. I manually entered all the mechanical parameters, i.e., Sd, Vas, Fs, Qms, Cms, Mms, so they wouldn't change. Modeled Qtc becomes 1.092.



And here's the purple line overlaid on the measured FR.



And for reference, a link to Infinity's published TS parameters: http://eu.infinitysystems.com/tl_fi.../Reference/Reference/1260w/REF1260W_PI_EN.pdf

Seems like this jives wih what dsg and LTD have been saying. I basically fiddled with BL and Le in WinISD until the peak of the curve as well as the points at 10 or 20 Hz, as well as 100 or 200 Hz, matched the curve of the measured FR. The higher end of the impedance curve (higher freq than what's posted above) and the Qtc aren't exactly on the money, but are much closer than they were.

When I get a chance I'll be measuring my HT18 D4s.

Comments? LTD or anyone else, did you have impedance-compensated TS params for any of the common drivers that you wanted to post?
 

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Just a few comments.

1. I'd rather see a 1m (or 2m or 10m) measurement done outside well away from boundaries than a close mic measurement for this. Close mic is ok but it's not really the same.
2. I'm pretty lazy and pretty busy at this time of year, I still haven't tried LTD's method of adjusting Bl and Le. I've only ever done Re and Eg (power) to gain back the losses from the added Re. I still have to go through LTD's method and then go through ALL the measurements again to correlate to the different measured designs - all the high inductance sealed designs at data-bass, the single ported design at data-bass, Submaximus, and Ricci's high inductance Othorn measurements with UXL and ZV3 (which were also close mic). Finding the right parameters with sealed box measurements and correlating (matching) sims to measurements of the more complex enclosures like horns is key. If you can do that you know you have a really useful, accurate and powerful tweak to work with.

Just typing all that seems like a lot of work, not sure when I'm going to actually get any of that done. I'm really interested to see how much more accurate LTD's method is. Adjusting Bl instead of Re seems to make sense, not sure how important it is to adjust Le as well, and I'm interested to see how all this correlates to high quality measurements, especially the Le adjustment part. I already know the Re and/or Bl tweak alone gets pretty close to measured results.

If anyone else has HIGH QUALITY accurate and repeatable measurements of ANY high inductance driver in ANY enclosure (especially more complex enclosures like ported, tapped horn, front loaded horn) it would be nice to have more to compare to. Enclosure details are necessary, more detail is better than less, exact dimensions would be nice (not just interior volume) as well as measurement details (power input, mic distance, etc) and measured t/s parameters. It's also nice to see measured impedance of the cab, the inductance hump(s) should correlate pretty well to the impedance spikes.

Nice to see this concept catching on, there's way to many garbage sims presented of high inductance drivers that are assumed to be accurate.
 

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I would model it like this with Unibox:
As previously discussed that's only going to work with enclosure types that Unibox can model, which isn't many. The inductance correction method I came up with works with any simulator, any driver, any enclosure.

And where did you get the Le2 and Re2 values from? I don't see anything in his measured parameters that says 4mh or 5 ohms. Have you verified that using Unibox for this is accurate and repeatable over a variety of different enclosures with the same driver?
 

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I am willing to mic my sealed ftw-21s ,but am not going to move them out of the basement to do it. So close mic is the best? 1" or what? And how much power? Does inductance increase with more power (seams like it would)?

Interesting to see how e.q. could be used to try and counteract the effects of inductance (if needed or desired). Though probably deminishing returns applies and each driver may react differently.

Can someone post links to inductance background and research? Maybe it has been shared, but I can't find it...
 

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As previously discussed that's only going to work with enclosure types that Unibox can model, which isn't many.
Which is just as many as everyone's favorite, WinISD.

And where did you get the Le2 and Re2 values from? I don't see anything in his measured parameters that says 4mh or 5 ohms. Have you verified that using Unibox for this is accurate and repeatable over a variety of different enclosures with the same driver?
The same place rhodesj got his new Le and BL from. They're made up to curve fit the model to the measured response.

Maybe I'm missing something... Why would it be less valid than any of the other parameter fudging? I didn't even change any of the basic measured parameters. At least Unibox has the hooks in place for entering parameters for inductance compensation and I simply entered values that bent the response to what was measured.
 

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I am willing to mic my sealed ftw-21s ,but am not going to move them out of the basement to do it. So close mic is the best? 1" or what? And how much power? Does inductance increase with more power (seams like it would)?

Interesting to see how e.q. could be used to try and counteract the effects of inductance (if needed or desired). Though probably deminishing returns applies and each driver may react differently.

Can someone post links to inductance background and research? Maybe it has been shared, but I can't find it...
The measurement distance depends on what the actual effective radiating radius of the driver is, so measure across the cone from the half way point of the surround. It will likely be around 18"/2 9". The measurement distance should be 0.10 times this number, so likely .9". This will provide an accurate measurement from 10hz up to 4311/ the radiating radius so likely 479 hz.

It is completely possible to get accurate quasi anechoic in room measurements from 10 hz up if you know what you're doing.
 

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It's seems ass backwards to modify actual data you get from measuring. I mean you can measure it with high accuracy, but if you go manipulating it or changing it then what's the point ? Seems like the process is backwards to me.
Well, REW generates parameters that are quite accurate. It even spits out a very high fidelity inductance model and one that's not quite as good (but still very good). Unfortunately, there is no enthusiast level software that can utilize either of the models. In the case of my Unibox "tweak", I'm effectively creating a lower fidelity inductance model (still much better than ignoring inductance).
 

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...and I simply entered values that bent the response to what was measured.
Making the figures up to match the curve is cool, but one needs to derive formulae from that info that works for all instances. Welcome to Theoretical Physics.
 

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Making the figures up to match the curve is cool, but one needs to derive formulae from that info that works for all instances. Welcome to Theoretical Physics.
This has already been done, read the posts OP referred to.

I've applied my correction method to sims with a variety of different high inductance drivers in a variety of different enclosures (sealed, ported, tapped horn, front loaded horn) and compared to measurements. And it works every time. Every driver in every enclosure. I can get the sims to match a high quality measurement (most measurements are from Josh Ricci) with a high degree of accuracy. Not perfect but a lot better than a regular sim.

I'm amazed that you guys think that this is just playtime in a simulator getting a curve to match a measurement by randomly tweaking the dials in a way that isn't repeatable or applicable to more than just that one measurment. You are not the first one to suggest this.

Welcome to due diligence.

I've spent a good bit of time on this. Do some due diligence of your own and read the suggested reading. Or just trust that I know what I'm talking about.
 

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Can someone post links to inductance background and research? Maybe it has been shared, but I can't find it...
The relevant posts are listed in post 1. There's a LOT of info.

I also posted this info in Popalock's big ported build thread, posted it in a thread on diyaudio last October, and posted random bits and pieces all over the place between then and now. I've shown 3 inductance corrected sims in different threads just today.
 

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It's seems ass backwards to modify actual data you get from measuring. I mean you can measure it with high accuracy, but if you go manipulating it or changing it then what's the point ? Seems like the process is backwards to me.
If you can take the measured t/s parameters and use them to get anything vaguely resembling an accurate sim that matches a measurement of a high inductance driver then be my guest.

This is the process that allows you to do that, repeatably, accurately, for any high inductance driver in any enclosure.
 

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And this flurry of speculation, opinion, and going off half cocked is exactly why I was happy to hide in the Hzhorn thread with a small audience to discuss this.

I hand you guys an inductance correction method on a silver platter and get nothing but complaints. This has been going on for months now every time I bring this up. Finally I got LTD on board, and that's most likely only because Ricci backed me up on this.

Come on guys, do a bit of reading before you start complaining. This really works, and it's endorsed by Ricci and LTD02.
 

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Which is just as many as everyone's favorite, WinISD.
As you know I'm not particularly happy with WinISD's limitations either. I reinstalled Windows last year and still haven't got around to putting WinISD back. It's not that useful IMO. Most of the things I sim can't be done in either WinISD or Unibox.

The same place rhodesj got his new Le and BL from. They're made up to curve fit the model to the measured response.

Maybe I'm missing something... Why would it be less valid than any of the other parameter fudging? I didn't even change any of the basic measured parameters. At least Unibox has the hooks in place for entering parameters for inductance compensation and I simply entered values that bent the response to what was measured.
Nothing wrong with this method of tweak til it matches the measurement.

BUT you have to do a few dozen comparisons to a bunch of different measurements in a bunch of different box types to confirm correlation, or all you did is randomly tweak the dials to get a result that may or may not be worth anything, same thing Augerhandle just accused me of.

I've done the work, I've done the comparisons, I've proved the correlation. My method works every time, every driver, every enclosure. Your method might work, but have you tested it?
 

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This has already been done, read the posts OP referred to.

I've applied my correction method to sims with a variety of different high inductance drivers in a variety of different enclosures (sealed, ported, tapped horn, front loaded horn) and compared to measurements. And it works every time. Every driver in every enclosure. I can get the sims to match a high quality measurement (most measurements are from Josh Ricci) with a high degree of accuracy. Not perfect but a lot better than a regular sim.

I'm amazed that you guys think that this is just playtime in a simulator getting a curve to match a measurement by randomly tweaking the dials in a way that isn't repeatable or applicable to more than just that one measurment. You are not the first one to suggest this.

Welcome to due diligence.

I've spent a good bit of time on this. Do some due diligence of your own and read the suggested reading. Or just trust that I know what I'm talking about.
Well, please forgive me. I did not see any referred posts in the OP, and know nothing of your work on the subject. EDIT: I wasn't responding to any post of yours, anyway.

 

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For those that don't want to read all the suggested reading just read this post.

http://www.avsforum.com/forum/155-d...asses-one-sub-126db-16hz-23.html#post31202121

This is what I posted back in October on diyaudio, and reposted in Popalock's build thread in January. This info has been out there for months. LTD02 recently helped improve my method a bit and it looks like he's getting even more accurate results than I was. I have yet to try his method, it's just a bit different but early results suggest it's a bit better. For those details you have to read the suggested reading mentioned in post 1.
 

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BUT you have to do a few dozen comparisons to a bunch of different measurements in a bunch of different box types to confirm correlation, or all you did is randomly tweak the dials to get a result that may or may not be worth anything, same thing Augerhandle just accused me of.

I've done the work, I've done the comparisons, I've proved the correlation. My method works every time, every driver, every enclosure. Your method might work, but have you tested it?
Have I confirmed that the inductance modeling capability of the software models inductance? Well, I sort of figured it works by design since that's the purpose of the feature.
 

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Well, please forgive me. I did not see any referred posts in the OP, and know nothing of your work on the subject. EDIT: I wasn't responding to any post of yours, anyway.

\If you want the backstory, read posts 224 through 330 in that thread: http://www.avsforum.com/forum/155-diy-speakers-subs/1908857-hzhorn-8.html#post33235473 The TLDR would be: diy speaker guy realized that higher-inductance drivers, when measured, don't match the performance predicted in their models. The real issue is that most modeling apps like WinISD or even HornResp don't use a detailed inductance model. dsg found a way to get more accurate results by adjusting Re and Power, and LTD02 countered by suggesting we adjust Bl, Qes/Qts, and Le. Tweaking the TS params in this way gets modeled results much closer to the measured ones.
That's the first paragraph of post 1 of this thread (minus the very first sentence). There's even a link.

I've been alternately ignored, mocked and ridiculed for even bringing this issue up since October. Please excuse me if I'm a bit touchy on this.
 
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