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Old 14th May 2006, 07:22 AM   #1
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Default please help with MJK's alignment tables

Anyone familiar with this excellent piece of work? I am interested in learning how to design without software, at least for early planning of transmission line subwoofers.

There are 4 tables. I understand the first table and the fourth table, regarding length and driver offset. I do not understand table 2 and 3 concerning dz and dr. I know they are used to calculate the shape but I don't even understand what shape function and resistance factor mean.

I know I'm new here but please don't tell me to read the article again, as I've studied it for hours and don't get it.
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Old 14th May 2006, 09:12 AM   #2
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You find Dz by looking on table 2, because you have both frequency and sl/so. Once you have Dz you can solve for Dr using the last function on page 3.

Dan
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Old 14th May 2006, 05:44 PM   #3
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Dan, thanks very much, but you are a bit above my level, I'm pretty new at this. Let's see if I understand what you are saying.

Choosing any value in table 1 shows you the tuning frequency and SL/SO for that particular length.

The corresponding spot on table two defines a value for dz. After this point it gets a bit fuzzy for me, probably mostly because I do not understand what shape function is or how it relates to what I am trying to do.

You said "Once you have Dz you can solve for Dr using the last function on page 3." I thought we got dr from table 3, defined by the driver's qts. Did you maybe mean take the values for dr and dz from tables two and three and use them to solve the last equation on page 3 to determine area of the closed end?

That would seem to make sense to me, because once you know SO you can calculate SL defined by the ratio chosen in table 1, and finally enough information to draw a design on paper.

If I am keeping up so far, that means there is only one formula to solve, correct?

There lies another problem, I only have grade 10 basic math. I could probably solve the equation, with the values of dr and dz from the table, the value of Re from driver specs (I assume), but what are the values of B, L and that symbol for acoustic impedance? And aside from the values, what are those 3 things?

That's a lot, so I'll just shut up now and thank you in advance for your help.
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Old 15th May 2006, 02:26 AM   #4
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?!?!?! another 15 year old interested in high end audio in ontario?! it simply cant be, i thought i was the only one.

sorry i cant help you with your question though, you are oviously beyond my level.
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Old 16th May 2006, 01:26 AM   #5
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15 was half a lifetime ago but I was never good at math so I quit math after grade 10.

I have a pretty good idea how to guess at proper size based on sd but it would be great to know how to use the tables to their full advantage.
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Old 16th May 2006, 02:10 PM   #6
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Maybe this question would be better suited for the full range part of the forum? I want to make subwoofers though, so I will leave it alone for awhile...
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Old 16th May 2006, 09:33 PM   #7
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ahhhhhh, you could always get a math nerd friend to do it for you.
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Old 16th May 2006, 11:10 PM   #8
qi is offline qi
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just a guy

Take a look at this thread...

http://www.diyaudio.com/forums/showt...731#post678731

There are two downloads in those posts.

Planet10's download of an AlphaTL article by Rick Schultz (post 9)

Give it a read

GM's xls spreadsheet from the same article (post 11)

Experiment with it (using the article).

This is a "simpler" way of doing TLs

It may help you get jump-started.

You will see that you only need three driver TS parameters.

Qts
Vas
Fs

Also, be sure to review the following...

http://www.t-linespeakers.org/design...ies/index.html

http://www.diysubwoofers.org/

Sure hope this helps...
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Old 17th May 2006, 06:28 AM   #9
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Hi, qi, the article "Pearls from..." is an excellent resource and was the basis for trying to figure out the alignment tables. There are two reasons why I am not interested in MJK's full works at this time.

First, if I can't manipulate the alignment tables I don't like my chances with the real deal. Second, my current project can't be modelled with his spreadsheets, but I'm still interested, even though my current project is past the planning stage I am interested in continuing to work with tl's.

Looks like I have a lot of studying to do with the alpha article and playing with GM's spreadsheet. Thanks for the info.
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Old 17th May 2006, 09:12 AM   #10
qi is offline qi
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Second, my current project can't be modelled with his spreadsheets
Ahhhhhhhh!

Another mystery wrapped in an enigma

Do you want to talk about it?
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