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Old 15th May 2012, 07:54 PM   #51
JMB is offline JMB  United States
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Join Date: Apr 2004
Location: Texas
Actually, Excel can do complex numbers but not sure how robustly it can do integration. I have seen some evidence that it can do simple integrations but not certain how complex it can get.

Earl, you are correct, MathCad is not available in a free form. I thought that I had seen it somewhere. There are some on the net that suggest that Smath Studio (freeware) is excellent software that is like MathCad lite and can even do calculus. I have to evaluate it to see.

jcx, I will have to take a look at Sagemath and Scilab.

If you would like me to do measurement comparisons, I should be able to get to it within a week or two and I would be happy to do it.

Jay
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Old 15th May 2012, 08:14 PM   #52
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Semi off topic

Mathcad, ugh.
While it might be expensive since they were bought out, a much bigger reason to avoid the new version is the company PTC that sells it now.

We had Mathcad back at intersonics starting at a very early version, later on, I bought it for home starting with version 7 and occasional upgrades throughout the years.
A couple years ago I decided to upgrade again to the latest version. To be honest, I canít say I had used it long enough to notice where /how it was different than 2001 when my computer HD crashed.
This is where they departed from what I was used to from real software companies.

With the new version was an additional licensing / authorization stage and after re-building my computer and re-installing all the software, I came to MathCAD which would not register / authorize.

I contacted PTC and explained the problem with the computer and after a number of e-mails back and forth trying to get it re-installed, they stopped replying.
Apparently, you are allowed to UN-install it and transfer to another computer, but you are only permitted one installation / license. Bottom line, they would not allow me to re-authorize the software and I had to re-install MathCAD back to version 8 to get to to run without the CD in the drive.

In my last e-mail I explained to PTC that I thought this was really crummy product support and whenever it was convenient, I would tell others of my experience with them, hence this post, YMMV.
Best,
Tom
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Old 15th May 2012, 08:49 PM   #53
gedlee is offline gedlee  United States
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Yep, PTC - they have ruined MathCAD. I gave up on upgrades since they took over. That's when I looked into Mathmatica. I won't buy another product from PTC. I'd rather switch to another program.
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Old 16th May 2012, 03:23 PM   #54
JMB is offline JMB  United States
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Here is an updated version incorporating Earl's suggestions. I am open to comments. Thanks, Jay
Attached Files
File Type: zip FF error with Eff Rad 1.024.zip (45.4 KB, 13 views)

Last edited by JMB; 16th May 2012 at 03:24 PM. Reason: typo
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Old 10th June 2012, 11:28 PM   #55
JMB is offline JMB  United States
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Just an update. I have now done measurements on several individual drivers in enclosures. I theorized that using a Bessel function to estimate the amount of effective reflection off of a baffle in combination with the trigonometric approach that Pat Brown (http://www.etcinc.us/tech/nl043_far_field_criteria.pdf) uses. My sense was that his approach overestimated the necessary farfield distance as it did not seem to take into account the loss of dispersion of sound as the frequency rises.

What I have found (and I will post my data and a new calculator that is consistent with my theory and my data) is that (this is not news) both the enclosure and driver play roles in the determination of farfield, but each contributes differently dependent upon the frequency range of interest.

One of the things that had always bothered me about Zaph's distortion measurements is that he (if I recall correctly) measured at 4 inches for tweeters and called this farfield. I do not believe this to generally be the case; certainly not from my measurements - realize, though, that there are different degrees of error that decrease as you measure further back and the definition of farfield really depends upon how much error you are willing to accept.

The calculator that I have developed (which, I am certain, also has some error associated with it as it is theoretical) using the Solver function in Excel. I am just trying to figure out how to make it so that you don't have to unlock the program, activate the solver function, and then relock the program. I think that I am pretty close in this regard.

As always, I welcome discussion and will welcome input once I can post this program.

One other comment is that my estimates do not seem to be as effective when wave guides are used. I suspect this is due to the change in beaming functions.
Jay
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Old 31st July 2012, 03:04 AM   #56
JMB is offline JMB  United States
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For a simplified yet experimentally verified version...I tested this with half a dozen drivers and various enclosures. Please feel free to comment, agree, disagree, or to grab a snack and ignore. Hope this is helpful. I appreciate all of the input along the way as my understanding is dramatically improved based upon your feedback.

Thanks,
Jay
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File Type: zip Farfield Distance Calculator d.zip (130.3 KB, 15 views)
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