about transmission line

hey everybody!

i have some questions about design and making transmission

line loudspeaker,i hope that i can get help here.

1 how to determine the length of the pipe(better explain with a

figure,because i am stupid:)

2 how to choose the loudspeaker?can i use a full range car

audio loudspeaker to do?

3 what's Q number?what's Qms,Qts n' Qes n' what's the

difference between them?what do they characterize?

4 i used some software to calculate the length of pipe,just

need to input Fo value n' Q value ,Q value here should be which

one?and the result of calculation was without volume of the box.

does it mean the volume doesn't effect to the final effect?

5 can i design a transmission line as a subwoofer?
 
kneadle said:
Start your journey there. Much happiness is down that path.

Or much frustration, followed by the realization that designing a good TL speaker is much more complicated than you ever imagined.

bigcatdairy said:
hey everybody!

i have some questions about design and making transmission

line loudspeaker,i hope that i can get help here.

1 how to determine the length of the pipe(better explain with a

figure,because i am stupid:)

2 how to choose the loudspeaker?can i use a full range car

audio loudspeaker to do?

3 what's Q number?what's Qms,Qts n' Qes n' what's the

difference between them?what do they characterize?

4 i used some software to calculate the length of pipe,just

need to input Fo value n' Q value ,Q value here should be which

one?and the result of calculation was without volume of the box.

does it mean the volume doesn't effect to the final effect?

5 can i design a transmission line as a subwoofer?


1. Line length is usually 1/4th wavelength of fs in free air, but is shorter usually because of stuffing.

2. You have to model speakers and/or use general rules for choosing good TL woofer.

3. Qms is mechanical losses, Qes is electrical losses, Qts is total losses 1/(1/Qms+1/Qts).

4. Don't know.

5. Yes, if I understand you question correctly.
 
THANKS GUYS!

I'LL TRY ANYWAY~BECAUSE I LOVE BASS!

AH~CAN U SUPPOSE SOME SOFTWARE FOR ME.

AND CAN ANYONE TELL ME SOMETHING ABOUT TL LOUDSPEAKER?

IN GENERAL ARE THE FACTORS OFFERED BY THE MANUFACTURER

RELIABLE?SOME BODIES TOLD ME THAT WE JUST NEED 2 USE

65% OF CALCULATION IS IT CORRECT?

HOW 2 CALCULATE THE AREA OF OPENING?

THANKS AGAIN~
 
bigcatdairy said:
AH~CAN U SUPPOSE SOME SOFTWARE FOR ME.

Go to www.quarter-wave.com like Kneadle said. You will find mathcad worksheets. I found them not to work with mathcad 12 and 11 (version 8 or 2000), but maybe my fault in not knowing the MathCAD software. I got MathCAD 2000 and now they work.

bigcatdairy said:
AND CAN ANYONE TELL ME SOMETHING ABOUT TL LOUDSPEAKER?

Like what? I can tell you that you cannot just pick any driver for a TL, but at the website already mentioned you will find you have severel options for TL enclosures.

bigcatdairy said:
IN GENERAL ARE THE FACTORS OFFERED BY THE MANUFACTURER

RELIABLE?SOME BODIES TOLD ME THAT WE JUST NEED 2 USE

65% OF CALCULATION IS IT CORRECT?

"65% of calculation" what does that mean? I would say they are not too reiable. Maybe some companies are reliable or more reiable than others, but I think it's hard information to come by. If you can measure them yourself do it. I'm trying to do it now, but it is not so easy.

bigcatdairy said:
HOW 2 CALCULATE THE AREA OF OPENING?

Hu? Do you mean taper? It's complex you must go to the websites mentioned and learn things. People will not and/or cannot help you if you do know the basics, that's why Kneadle sent you to those websites. Understand?
 

RJ

Member
2004-10-19 4:29 pm
What is you e-mail address?
I'll send you a program for calculating T-Lines.
Here's the formula for a 1/4 wave t-line;

(1128/Fs)/4 = 1/4 wave in feet
Feet x 12 = length in inchs.

An example:
1128/50 fs = 22.56/4 = 5.64 Ft.
5.64 x 12 = 67.68 inches.
That would be the length of your pipe.

T-Line Subs are possible but sound different then closed or sealed subs. Go sealed or horn-loaded. Ported is Ok but it's better if you go Dual-Chambered bass Reflex.

The pic is of my favorite T-Line; A 112" Labyrinth for 5 1/4" drivers.
 

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Re: Re: about transmission line

Jimmy154 said:
1. Line length is usually 1/4th wavelength of fs in free air, but is shorter usually because of stuffing.

It is a 1/4 wl (less end correction in a straight pipe, shorter in a taper pipe (closed end bigger than terminus end), longer in a flared pipe (losed end smaller than terminus end). The stuffing has little or no effect on length.

2. You have to model speakers and/or use general rules for choosing good TL woofer.

The gerneral rules (classic line) don't work all that well.

dave
 
Re: Re: Re: about transmission line

planet10 said:
It is a 1/4 wl (less end correction in a straight pipe, shorter in a taper pipe (closed end bigger than terminus end), longer in a flared pipe (losed end smaller than terminus end). The stuffing has little or no effect on length.

I remember reading a few days ago that you had to adjust line length after you add sfuffing in one of these PDF's http://www.quarter-wave.com/Project01/Project01.html

Maybe it's not a lot though?

planet10 said:
The gerneral rules (classic line) don't work all that well.

I guess you have to model a woofer then.
 
You will find mathcad worksheets. I found them not to work with mathcad 12 and 11 (version 8 or 2000), but maybe my fault in not knowing the MathCAD software. I got MathCAD 2000 and now they work.

I have used all of the recent MathCad releases to develop and run my worksheets. I am now using release 12. What specifically were the symptoms when you tried to run the worksheets using MathCad 11 or 12?

MathCad 2000 is without question the most stable release I have worked with and I go back as far as version 4. I am surprised you had problems with MathCad 11 since it was almost as stable as 2000. MathCad 12 would not run the worksheets right out of the box because of MathSoft screw ups, they released a patch very quickly to correct programming problems so now it runs the worksheets OK (just barely OK in my opinion). MathCad 12 is very S L O O O O W.

But MathCad 12 is still prone to crashing and I have been very unhappy with this release. MathSoft got a very blunt e-mail from me questioning if they even did any beta testing before pushing version 12 out to the users. I am not sure what I am going to do about version 13 (lucky or unlucky?). Many other engineers have also expressed their dissatisfaction with version 12, my former employer would not buy the upgrade.

If you tell me what happens with 11 and 12 (aftre loading the 12.1 patch) I might have a few suggestions for fixing the problem.
 
Hi,

MJK said:
If you tell me what happens with 11 and 12 (aftre loading the 12.1 patch) I might have a few suggestions for fixing the problem.

The graphs did not show up in 11b and 12. So I got 2000 and they show up. I no longer have 11b and 12 on my pc.

Your Focal 8V 4412 mid-bass driver does not seem to model very well as a TL. Does the stuffing placement, driver offset, and/or driver position ratio fix the wavey appearance of the SPL graph (modes is that what you call what causes the waves) in TL Open End.mcd?

I'm asking cause I have an Eton 8-800 with similar specs that models the same as the focal in TL Open End. Maybe I'm bad with that worksheet. Seems to model much better as a ML TQWT. How come folded ML TQWT's, at least all the ones I've seen, have the small ends towards the front of the enclosure? I would like to have the big end towards the front of the enclosure, giving me a slightly more favorable driver position ratio of .56 compared to .4. But they are pretty similar, that's why I ask you if there is a reason folded ML TQWT have the small end towards the front of the cabinet.
 
I have no idea why 11b did not work, I used 11 for a long time without any trouble. If you did not load the patch for 12 that is why things did not work, in general a lot of people had problems with the first release of 12 running all kinds of worksheets.

Does the stuffing placement, driver offset, and/or driver position ratio fix the wavey appearance of the SPL graph (modes is that what you call what causes the waves) in TL Open End.mcd?

Yes, those all help tame the ripple. You will always have some amount of ripple, humps, bumps, and depressions in the plotted SPL responses of TL's and many other enclosures. You need to recognize that most of the box design freeware does not calculate these due the lumped parameter modeling, they are always there. I don't worry too much about 1 or 2 dB wiggles in the SPL curves. When you add baffle step, floor bounce, and other room influences these small wiggles tend to be the least of your problems. Try the "Offset Driver" worksheet to study the impact of moving the driver 0.2 to 0.33 of the way down the TL.

How come folded ML TQWT's, at least all the ones I've seen, have the small ends towards the front of the enclosure? I would like to have the big end towards the front of the enclosure, giving me a slightly more favorable driver position ratio of .56 compared to .4. But they are pretty similar, that's why I ask you if there is a reason folded ML TQWT have the small end towards the front of the cabinet.

Absolutely no reason the bigger section could not be in the front if the desired driver placement fits the geomtry. I have not built a folded ML TQWT, but I see nothing that would be compromised if the layout was as you have described.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
After several attempts to use Martin King's worksheets, I finally got to the point where I can use them easily. Well, not as easy as WinISD orSubwoofer Simulator, but neither of those programs do what Martin's worksheets do in calculating resonances.

I have not yet built a Transmission Line-just worked with the worksheets. However, several people on the forum have tested the Transmission Lines built according to Martin J King's software and found good agreement between the calculation and the real result. That's good enough for me.

A couple of hints-remember, I only figured out how to use the software, so if anyone has built one and disagrees with anything I say, please feel free to jump in and correct.

A) Do you have Norton Anti-Virus? If so, you must disable script blocking-just shutting off Norton will not do it. I will include instructions on how to do this.


B) A Transmission Line is a close cousin of the Ported Box, and they have similar bass outputs in most configuration. The stuffing of the Transmission Lines can change things, but Martin J King's software tells you how. So if you want some place to begin, let's plan a Ported Box, see if the response is in the neighborhood, then transfer it over to the Transmission Line. Then we can make changes to the Transmission Line and see the result on Martin J. King's graphs.

C) I'll post various graphs to help you along, and you can make design decisions based on what you see there.

So let's give it a try. We'll plan one together, and the more experienced Transmission Line builders can give us their advice.

So: do you have a specific driver in mind? If so, please tell us what it is and post the Thiele-Small* parameters if possible.

If you do not have a specific driver, can you tell us about how large you want the box to be and what kind of bass output you were hoping for? Remember, the box will be somewhere in the neighborhood of a Ported Box-maybe a little larger to compensate for stuffing.


*Thiele-Small parameters are such things as Qts, Qes, Qms, Vas, Fs, Sd, etc. Don't worry about what they mean right now-we'll get you through it.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Here is a link where instructions are included on downloading free MathCAD demo, (be careful, it can be tricky), and disabling Norton script blocking, if you have Norton. Caution-I made a mistake in this thread on post #18, but I immediately corrected it, so watch for the correction.

The free MathCAD demo plus Martin's free worksheets are all you need to calculate Transmission Line response. Some go ahead and buy the MathCAD program, but the free demo is all you need, and that is what I use. So the whole thing is freeware, if you want it to be. :)

PS: The free demo does not have a time limit. I downloaded it a couple of years ago and it still works. The only difference between the free demo and the full program are some features that are nice, but not necessary for graphing Transmission Line response.
 
Jimmy154 said:


Go to www.quarter-wave.com like Kneadle said. You will find mathcad worksheets. I found them not to work with mathcad 12 and 11 (version 8 or 2000), but maybe my fault in not knowing the MathCAD software. I got MathCAD 2000 and now they work.

Like what? I can tell you that you cannot just pick any driver for a TL, but at the website already mentioned you will find you have severel options for TL enclosures.

"65% of calculation" what does that mean? I would say they are not too reiable. Maybe some companies are reliable or more reiable than others, but I think it's hard information to come by. If you can measure them yourself do it. I'm trying to do it now, but it is not so easy.



Hu? Do you mean taper? It's complex you must go to the websites mentioned and learn things. People will not and/or cannot help you if you do know the basics, that's why Kneadle sent you to those websites. Understand?

can i take a caraudio driver then do it?because i can not find any

good driver for my tl in this city except car audio driver.can u

suppose me any good choice?

65%of calculation means the length of path.i have read that side.

thanks!




RJ said:
What is you e-mail address?
I'll send you a program for calculating T-Lines.
Here's the formula for a 1/4 wave t-line;

(1128/Fs)/4 = 1/4 wave in feet
Feet x 12 = length in inchs.

An example:
1128/50 fs = 22.56/4 = 5.64 Ft.
5.64 x 12 = 67.68 inches.
That would be the length of your pipe.

T-Line Subs are possible but sound different then closed or sealed subs. Go sealed or horn-loaded. Ported is Ok but it's better if you go Dual-Chambered bass Reflex.

The pic is of my favorite T-Line; A 112" Labyrinth for 5 1/4" drivers.


my e-mail adress is [email protected] what about u?
 
program for calculating T-Lines.

What is you e-mail address?
I'll send you a program for calculating T-Lines.
Here's the formula for a 1/4 wave t-line;

(1128/Fs)/4 = 1/4 wave in feet
Feet x 12 = length in inchs.

An example:
1128/50 fs = 22.56/4 = 5.64 Ft.
5.64 x 12 = 67.68 inches.
That would be the length of your pipe.

T-Line Subs are possible but sound different then closed or sealed subs. Go sealed or horn-loaded. Ported is Ok but it's better if you go Dual-Chambered bass Reflex.

The pic is of my favorite T-Line; A 112" Labyrinth for 5 1/4" drivers.

hello, Rj
My email address is [email protected] Can you mail me program for calculating T-Lines.

Thank You