Augspurger's alignment tables

[Dave Jones]

I have a question about Augspurger's alignment tables. I found the articles at http://www.yildiz.edu.tr/~ilkorur/de...s/AES_5011.pdf.

I did some calculations using the alignment tables that came up with a total volume that appeared far too small. Using the "Table 1" alignment for a tapered pipe with a Qt of 0.4, I interpolated a volume of about .2 cubic feet. I expected something around a .75 to 1.4 cubic feet. Then I found the following sentence (refering to a different alignment for a straight pipe) on page 4 of part II: "Qts is about 0.5 and pipe volume is twice Vas." But the the chart shows Vas/Vp = 2.0. Obviously it should read, "Vp/Vas = 2.0."

So my question is, are all the ratios inverted? I think they may be. Interestingly, if I use the "coupling chamber" alignments and assume all the ratios are inverted, I come up with something that's not too dissimilar to the design that I originally questioned http://www.ejjordan.co.uk/enclosures.html. (The Fp of 45*0.5 = 22.5 is off the chart, and would extrapolate to a line somewhat longer than the design.) Notice also that the stuffing density would be very low. The Jordan design appears to call for stuffing only in the top chamber.

Is it the case that all the ratios are reversed?

[Dave Jones]

On the other hand, arguing against the posibility that, for example, Fs/Fp really means Fp/Fs, there's this: The current AudioXpress issue, which cites Augspurger's work, touts lines that are as little as half the quarter wave length of Fs. If I turn Fs/Fp upside down (like Vas/Vp), I get a line about twice that length. So now I'm thinking only Vas/Vp is upside down.

[Dave Jones]

Yikes! I still don't get it. How can you reconcile the following chart and text?

(3b) Fs/Fp = 0.33

'Figure 3b shows how a nominal 109Hz pipe can be "tuned" to 65Hz."

The only simple way I can think of to combine 109 and 0.33 and come up with something around 65 is this: 109*(1-0.33) = 64.3, which ain't no ratio.

Help! Can someone who understands this paper work through and example? Maybe start with the JX92S and show how to design a straight line system? Then we could compare it to the design in this month's AudioXpress.

[Dave Jones]

It gets even stranger. I found a snippet of what's supposed to be an Augspurger alignment table here: http://www.madisound.com/audioXpress...r%20Review.pdf

The numbers don't bear any resemblance to the ones in the paper. Double HELP!

[Bricolo]

Originally posted by Dave Jones
It gets even stranger. I found a snippet of what's supposed to be an Augspurger alignment table here: http://www.madisound.com/audioXpress...r%20Review.pdf

The numbers don't bear any resemblance to the ones in the paper. Double HELP!

the table in the audioxpress review is the extended table
this one gives lower bass, but also bigger cabinets

[kelticwizard]

Dave:

I have not had time to review the paper. I will do so, however.

The only thing I can say is, by the time these things are submitted to a professional journal such the Journal Of The Audio Engineering Society, I think we can assume thay have been proofread. So I am inclined to think there is no inversion.

I will read the paper and get back to you.

[Dave Jones]

Originally posted by kelticwizard
Dave:

I have not had time to review the paper. I will do so, however.

The only thing I can say is, by the time these things are submitted to a professional journal such the Journal Of The Audio Engineering Society, I think we can assume thay have been proofread. So I am inclined to think there is no inversion.

I will read the paper and get back to you.

The alignment tables are just some numbers, no doubt the output of a computer program. The numbers don't bear any resemblance to some other numbers I saw in AudioXpress which are supposedly from the same source. So if both sets of numbers are correct, then they must mean different things. So what do they mean?

I don't know anything about the journal, but ... I've found many mistakes in other journals. My master's thesis was a proof of "Dehn's lemma." Other proofs of that lemma had been published in international refereed journals going back to 1910. Every time a proof got published, a couple of decades later someone would find a hole in it. To this day, a 1957 proof is widely considered correct, a view I did not share in 1979 when I got the master's degree.

My first foray into this group, oh these several weeks ago, was to ask if a particular capacitor value (2uF) in an article that's been on a high traffic web site for a long, long time wasn't too small. Eventually I got in touch with the author, a very highly respected loudspeaker system designer, who suggested I use a 4-5 uF cap. Even real smart people make simple mistakes and typos.

Hmmm. It may sound like I get my jollies finding mistakes that smart people make. Nope. I've just that in my line of work I have learned to be very careful about such things.

[Dave Jones]

Originally posted by kelticwizard
Dave:

I have not had time to review the paper. I will do so, however.

Muchos gratias!

[Dave Jones]

Originally posted by Bricolo



the table in the audioxpress review is the extended table
this one gives lower bass, but also bigger cabinets

Even so, several of the questions I brought up still puzzle me.

[Dave Jones]

Originally posted by Bricolo



the table in the audioxpress review is the extended table
this one gives lower bass, but also bigger cabinets

Is there a way to obtain the tables from Speaker Builder without buying one or two years of back issues?