Help a new guy with TL enclosure

thematrimix · 2010-03-01 10:08 pm

Hello,

I have been very tempted to build a set of tower speakers lately, but have pretty much no knowledge as to the design. So with that I started searching and found a design that I like quite a bit.

scoperta

I could simply copy it, but I want to do full range set up maybe with a Jordan JX92S.
Here comes the issue. I need to update the design for the JX92S.
Any help is appreciated.

Thank You

thematrimix · 2010-03-01 11:04 pm

Or with the design should I stick with a two way set up?

GM · 2010-03-01 11:30 pm

Mercy! Don't those look nice!

Anyway, there's several popular designs around here for it as well as some new ones that are tuned a bit lower for rooms and/or speaker positions that yield enough gain down low, so do a forum search, there's a bunch of threads.

GM

thematrimix · 2010-03-02 5:54 am

Well I have done some work in Google Sketch so that when I need to make changes I can do easily. I will post the pic here so all can see. It is nothing special, but it took me a while as I am not a cad person of any type. So, any help with determining the changes one would need to make to go full range would be greatly appreciated. I am not dead set on the Jordan JX92S, but they seem like a good choose or maybe Fostex FX120 as many people seem to like them aswell. Well, I will have to see what I can come up with.

Thanks

planet10 · 2010-03-02 6:07 am

I much prefer the FX120 (which i like) to the JX92 (which i don't).

To get good results from the TL you will need to run the driver parameters thru Martin King's alignment tables (at least).

dave

thematrimix · 2010-03-02 3:30 pm

planet10 said:
I much prefer the FX120 (which i like) to the JX92 (which i don't).

To get good results from the TL you will need to run the driver parameters thru Martin King's alignment tables (at least).

dave

I think there in lies the problem. I do not know much about the tables and how to use them. I have done some reading on it, but that is more math than I have looked at since cal 2 in collage. And then which one to use. I see at least 4 or 5 of them.

planet10 · 2010-03-02 6:36 pm

I probably should have linked the page & not the document. There is also a download for a spreadsheet that does all the math for you.

Transmission Line Theory

dave

mondogenerator · 2010-03-03 1:53 am

yup there is

i can second that. the Excel based spreadsheet, by Keith Webb, on the site is very easy to use, even for a novice.

http://www.quarter-wave.com/TLs/Alignment_Tables_Calculator_3_3_09.xls

Hell i used it and ive never ventured into TL design before the present design im building!

some of the symbols used may seem meaningless unless you read at least SOME of MJK's write-ups:

ie. Dz = distance from closed end to driver centre

there may be others but i struggle to remember without it in front of me!

either way, theres plenty of people here that can help if you still require any, once youve got the spreadsheet calculator.

Good luck

thematrimix · 2010-03-03 2:08 am

mondogenerator said:
i can second that. the Excel based spreadsheet, by Keith Webb, on the site is very easy to use, even for a novice.

http://www.quarter-wave.com/TLs/Alignment_Tables_Calculator_3_3_09.xls

Hell i used it and ive never ventured into TL design before the present design im building!

some of the symbols used may seem meaningless unless you read at least SOME of MJK's write-ups:

ie. Dz = distance from closed end to driver centre

there may be others but i struggle to remember without it in front of me!

either way, theres plenty of people here that can help if you still require any, once youve got the spreadsheet calculator.

Good luck

I thank oyu all very much. I will sit down and run all the numbers tonight or tomarrow sometime and see what comes up. I did read a good bit of the papers that the previous guys link took me too and got some good info from it.

Again thanks

thematrimix · 2010-03-04 3:21 am

Have a question on where I am to get two values in required for the sheet.

For Fostex FX120:
Sd = ? I did some googling and came up with 66.5cm2, but have to clue if this is correct. The site PDF does not have the value.
BL = ? Not sure on this.

Any help on getting these values would be greatly appriciated.

GM · 2010-03-04 5:30 am

Bl is the "B" or gap flux times the "l" or length of wire in the gap, so is an electrical motor force factor.

There's a bunch of math to calculate it that I can post or you can do as most folks and input T/S specs in WinISD, Hornresp or other box program that calculates it.

Anyway, using the T/S published specs plus:

Sd = 66.476 cm^2
SoS = 344 m/s SoS
air density = 1.21 kg/m^3

Bl = 5.2062 N/A.

Inputting the specs into Hornresp returns 5.21 N/A, so looks like I did the math right.

GM

thematrimix · 2010-03-05 1:29 am

GM said:
Bl is the "B" or gap flux times the "l" or length of wire in the gap, so is an electrical motor force factor.

There's a bunch of math to calculate it that I can post or you can do as most folks and input T/S specs in WinISD, Hornresp or other box program that calculates it.

Anyway, using the T/S published specs plus:

Sd = 66.476 cm^2
SoS = 344 m/s SoS
air density = 1.21 kg/m^3

Bl = 5.2062 N/A.

Inputting the specs into Hornresp returns 5.21 N/A, so looks like I did the math right.

GM

Thanks for the help.

I have inputed all the values into the sheet. The only value I do not know what it is for is: SL/SO and how it effects everything. And of course what it all means. About the only thing I get out of it is that the TL needs to be 45.74 inches.

Thanks for the help Guys and Gals

planet10 · 2010-03-05 2:39 am

So/Sl defines the rate of taper.

The spreadsheet is missing one essential piece of info... the driver offset (driver centre to closed end), which works out to 15.53"

dave

mondogenerator · 2010-03-05 2:47 am

planet10 said:
So/Sl defines the rate of taper.

The spreadsheet is missing one essential piece of info... the driver offset (driver centre to closed end), which works out to 15.53"

dave

yep the length Dave mentions is the value Dr (i think! lol although i quoted the wrong one before.....) times the total length to give the offset.

i think i got that right :devily:

One thing i WOULD recommend doing is adding some resistance to the Re value (or DCR) for the speaker, to account for the change in Qes when the wire resistance to the amplifier is factored in.

Its amazing how much a fraction of an Ohm alters the TL design.

For my design i guess-estimated about 0.5 Ohm, taking my Re from 5.6 to 6.1 Ohm, but it all depends how long a run of cable youre going to be using, and since yuour using a full range driver, with NO series coils added to tailor response (i assume), then i would guess adding up to 0.2 Ohm or thereabouts would be sufficient to cover any length amp cables. Within reason of course!

GM · 2010-03-05 7:57 am

thematrimix said:
Thanks for the help.

I have inputed all the values into the sheet. The only value I do not know what it is for is: SL/SO and how it effects everything. And of course what it all means. About the only thing I get out of it is that the TL needs to be 45.74 inches.

You're welcome!

Hmm, I wonder why the Excel SS I downloaded recently is so different than yours? The one I have isn't as pretty, but it explains, what SO/SL means and calculates the driver offset position (DOR). Regardless, MJK's tutorial explains all this, complete with drawings and an example design.

GM

GM · 2010-03-05 8:03 am

mondogenerator said:
yep the length Dave mentions is the value Dr (i think! lol although i quoted the wrong one before.....) times the total length to give the offset.

'DOR' (driver offset position), 'Dr' is the resistance (damping) factor (Qts).

GM

Henkjan · 2010-03-05 12:57 pm

here is my version of a spreadsheet for the allignment tables

thematrimix · 2010-03-05 3:21 pm

Henkjan said:
here is my version of a spreadsheet for the allignment tables

Quick question, what is Qtd and fd?
Fb = tuning freq
Qts = the total Q of the driver at Fs

I get all the values from Audio Glossary.
A useful little site, but I do not see either of the values and I don't know what they are.
Sorry for the ignorance, but the sheet looks nice.

Thanks you guys are great and helpful and I am enjoying the learning.

After this I plan on building a sub with a Image Dynamics IDMaxx I have that I am not using.

GM · 2010-03-05 3:25 pm

That's the one I have, thanks for sharing! One of these days I need to learn how to do macros.........

GM

GM · 2010-03-05 3:34 pm

You're welcome!

Yes it is, thanks for pointing it out.

MJK insists on using his own terminology in some cases:

Fd = driver Fs
Qmd = driver Qms
Qed = driver Qes
Qtd = driver Qts
Vd = driver Vas

There may be others, but these are the only ones that come to mind ATM.

GM

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