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Discussion Starter · #1 ·
Hi, new member here
I've decided to build a transmission line box, I've read all the web sties on 1/4 wave length and found a good calculator. Maybe some one with more experience can help me.
I have all the driver data at hand.

Fs : 66.5hz
qts: .411
qte: .425
qms: 12.336
qtp: .411

Sd: 113.04cm^2

What should be my TL length and area be for this driver?
Do I do a tapered or non tapered?
Im going to fab this up in solidworks and will gladly share my plans.


I've found this calculator but don't trust/know the unit inputs, maybe some can help

http://www.members.tripod.com/oakleyspeakers/index.htm


thanks
 

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Welcome aboard!

I know absolutely nothing about TL, but hopefully someone more knowledgeable can chime in. It seems like an interesting project...i'd love to see the outcome ;)
 
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Discussion Starter · #4 · (Edited)
Well i'll be contacting him, this is what I got so far, length and sd is correct depending on which book you go by.
I use the program solidworks, it is very cool and easy to use.
Each tower is one sealed 12" sub, two 6.5" and two 1" tweeters.
It is 42" tall and 15" or so deep





 

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Premium Member
Joined
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8,367 Posts
Hi, new member here
I've decided to build a transmission line box, I've read all the web sties on 1/4 wave length and found a good calculator. Maybe some one with more experience can help me.
I have all the driver data at hand.

Fs : 66.5hz
qts: .411
qte: .425
qms: 12.336
qtp: .411

Sd: 113.04cm^2

What should be my TL length and area be for this driver?
Do I do a tapered or non tapered?
Im going to fab this up in solidworks and will gladly share my plans.


I've found this calculator but don't trust/know the unit inputs, maybe some can help

http://www.members.tripod.com/oakleyspeakers/index.htm


thanks
There are two critical factors for TL systems..
One is that the wavelength must be exactly a quarter wave, unless you want to build a monster box for a half wavelength..
The other is the dampening material that's used in the transmission path...The type and the amount..
When I built TL speakers I used a fibrous wool right through the line..

Also for best results the line should be tapered gradually all the way to the port opening..

The port opening should be as wide as the box and the same height as the outlet of the line..
I used high fs. 12" speakers, with similar specs. to your own..Low fs speakers are not suitable as they cannot get enough loading..

The width of the box is not critical, and if you're using a 12" driver I would make the box about 18" wide..

I hope that is of some help...

EDIT...I've just spotted your drawings...one thing I would suggest changing is to have your bass driver at the top of the box..This gives a cleaner, well defined bass..
 
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Discussion Starter · #6 ·
Ok for my wavelength have 66.5hz = 16.992 feet * (1/4) = 4.248 feet for my line
My filler is dacron, i'll put more by the speaker and less down the line, maybe .5 lbs worth total per line.
Yeah I haven't added my ports on the rear yet.

What your saying is, my port exit should be 1.0 *the SD right?
And the start of my line should be 1.5 Sd?
So it goes from 1.5 to 1.0 for 4.28 feet yes?
 
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Discussion Starter · #7 ·
Here is a close up of my line taper, I was going to try to do it horizontally, but this was my first attempt at modeling it.
What happens if my line is to long?
Where does the "line" start? Does it start at the speaker? Does it start at the mouth of the 1.5sd inlet?

 

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8,367 Posts
Forget everything I said...I see from your last post that you're not even using the 12" driver in the line, but as just a selaed sub...
If you're using the two 6.5" drivers as your Bass/midrange speakers, then that multi folded line is not going to give you strong deep bass with those higher Fs. speakers...There will be too much loading..
 

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I have to say that that is not a true transmission line.. both speakers should be in the same path or otherwise you will have phasing problems..
I will try a draw you a rough sketch of how it should be and post it to you a bit later..Oh and Dacron in that restricted path will be too dense..
 
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Discussion Starter · #10 ·
Ok, I thought that might be the case (to much loading), i'll try to design a true long tapered one next.....
Question about drivers in the line, can you put two drivers of the same type in the same line?
If so what happenes to the specs of the line?
 
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Discussion Starter · #11 ·
Thank you that would be great, putting both the drivers in the same line solves a lot of things.
How accurate are these transmission lines, 1/4 wave lenght exact? I know it's an art... but
I don't want to put tons of trouble into building it when it's not worth the results.
 

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Premium Member
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8,367 Posts
There is a reasonable tolerance in the length of the path...
The actual wave is measured through the centre line of each chamber in the line..This is difficult to do when you are only using a measuring tape or the like, but close enough will be good enough..
Tolerance would be about plus or minus 1"..

This a conventional design for a TL..If the height of the box is not a problem, then you can do away with the last chamber and have the port at the bottom..

 
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Discussion Starter · #13 ·
Hi Scoey, for your driver I would set the tuning frequency to 50 Hz. You can get some ideas from the Alignement Tables on Martin J. King site www.quarter-wave.com

Also read my article http://www.t-linespeakers.org/design/MJK-for-dummies/index.html

And this one: http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf

I hope this can inspire you. Please note: Adding 2 drivers change the design of the TL, as the Vas doubles and other T/S change as well. Meaning, the volume should be increased.

Hi from Bjorn
 

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I built one 8" TL sub - or rather tried to build. The advice from my experience - make sure you make it so you can access the inside to change the stuffing. Even though I wasn't happy with my TL, I've heard many I've liked a lot. The bass is very natural and cool sounding.

Also, listen to Bjorn - he knows what he's talking about.
 
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