Dual 8" T-line build

[Flamin_D_Audio]

Ive been doing home / car audio for a long time now and have lots of experience with ported and sealed enclosures, and as a project want to build a t-line for two 8" drivers, with the aim of getting them to hit as hard and low as possible (30hz).

Ive researched and seen loads of variations, like some that are just folded lines, some that have a chamber before the line, some where the like gets wider, etc.

I know my line needs to be 112.5" long to get the 30hz tuning i want, as im doing 1/4 wavelength. (Let me know if doing 1/2 wavelength will be considerably better).

Just a few things to help me out:
- How wide should the line be? Ive got a feeling its to do with the drivers Q** values?
- Should it be a simple line, or have a primary chamber before the line?
- Should the line widen?
- Is there a 'best side' that the line should exit?

Any help with this would be great, cheers for reading!
Sam

 

[lsiberian]

Ive been doing home / car audio for a long time now and have lots of experience with ported and sealed enclosures, and as a project want to build a t-line for two 8" drivers, with the aim of getting them to hit as hard and low as possible (30hz).

Ive researched and seen loads of variations, like some that are just folded lines, some that have a chamber before the line, some where the like gets wider, etc.

I know my line needs to be 112.5" long to get the 30hz tuning i want, as im doing 1/4 wavelength. (Let me know if doing 1/2 wavelength will be considerably better).

Just a few things to help me out:
- How wide should the line be? Ive got a feeling its to do with the drivers Q** values?
- Should it be a simple line, or have a primary chamber before the line?
- Should the line widen?
- Is there a 'best side' that the line should exit?

Any help with this would be great, cheers for reading!
Sam

My suggestion is that you contact TLS Guy directly. He's an expert on what your trying to do. I'd follow every suggestion he gives.

If your interested in building a pair of really good TLs already mapped out. I suggest Thor TLs. Those things are really good.

For a sub I suggest the Kappa project.

 

[TLS Guy]

Ive been doing home / car audio for a long time now and have lots of experience with ported and sealed enclosures, and as a project want to build a t-line for two 8" drivers, with the aim of getting them to hit as hard and low as possible (30hz).

Ive researched and seen loads of variations, like some that are just folded lines, some that have a chamber before the line, some where the like gets wider, etc.

I know my line needs to be 112.5" long to get the 30hz tuning i want, as im doing 1/4 wavelength. (Let me know if doing 1/2 wavelength will be considerably better).

Just a few things to help me out:
- How wide should the line be? Ive got a feeling its to do with the drivers Q** values?
- Should it be a simple line, or have a primary chamber before the line?
- Should the line widen?
- Is there a 'best side' that the line should exit?

Any help with this would be great, cheers for reading!
Sam

You have a lot of research to do before you can deign a good TL.

You certainly don't want a 1/2 wave pipe, that would be an open pipe with harmonics galore and be very long.

From Martin King's site this shows the relationship of pressure and velocity for the fundamental and third and fifth harmonics for a closed pipe. A TL bleongs to the Gedackt organ pipe family. A closed pipe emits odd order harmonics, an open one even order harmonics.

The pipe length Lp is a function of driver fs and Qts. The volume of the pipe Vp is related to VAS.

You can not get a lower F3 point from a driver by mismatching the line.

Not all speakers are suitable for TL loading. High Fs and low Qt is impossible to work with.

What are the T/S parameters of your drivers?

This article by Joe D'Appolito should be a good starter for you.

In general a line should have about a 3:1 reverse taper over its length. To be aperiodically critically damped, so you get no bass hangover, just tight natural bass, the line needs to be stuffed to the point where you get just one peak of impedance, not two. The roll off will then be second order 12db per octave rather than 24 db per octave, of an unstuffed line or bass reflex.

If you click on my signature you will see soem of my TLs. Here is a link to the build album

You are getting me at a slightly bad time as I'm getting ready to fly to the UK Friday with a trip to the Isle of Man a week from today.

 

[Flamin_D_Audio]

You have a lot of research to do before you can deign a good TL.

You certainly don't want a 1/2 wave pipe, that....

Thank you, thats helped a great deal!

Thats enabled me to construct a first design of the box - i have doubts about parts of it - but its a start. Tell me what you think and what areas to change for improvement!

(if the photos below dont show, use these links: 1, 2, 3, 4)

As you can see the line starts off at 2" wide and ends up 5" wide.
Some issues i think i have are:
- the chamber is too large
- the box volume is too big
- the expantion of the line is too great

The drivers ill be using to start with probably arent well suited for t-line enclosures; but theyre only temporary untill i can afford some RE8s which look good for this purpose.
Thanks for all your help so far
Sam

 

[TLS Guy]

Thank you, thats helped a great deal!

Thats enabled me to construct a first design of the box - i have doubts about parts of it - but its a start. Tell me what you think and what areas to change for improvement!

(if the photos below dont show, use these links: 1, 2, 3, 4)

As you can see the line starts off at 2" wide and ends up 5" wide.
Some issues i think i have are:
- the chamber is too large
- the box volume is too big
- the expantion of the line is too great

The drivers ill be using to start with probably arent well suited for t-line enclosures; but theyre only temporary untill i can afford some RE8s which look good for this purpose.
Thanks for all your help so far
Sam

That is what is known as a labyrinth type of TL.

You are tapering it the wrong way. Also the gap between the drivers should be 1/5 of the distance form the closed end. Off set lines have the smoothest response.

It is better if there is no throat.

Put the drivers on the opposite side off the enclosure, and make that the closed end. Make the pipe wide enough at that point that there is room for the driver and and 3 inches behind the magnet and taper the pipe 3:1 or 4:1

So if the speaker chamber is 6 inches deep, the port should be 2 inches high.

If you use a 4:1 taper then you can make the speaker chamber 8 inches deep and taper to 2 inches. That will likely work best as you will have good space behind the drivers.

If you can slope the panels like this, it would be better.

You are getting me at a bad time. I fly to England tomorrow evening. I will have internet at Rochester after I rest and turn around. However I make my way to the Malvern Hills Sunday and on to the Isle of Man Monday. I will make my way back to Rochester Thursday. So there will be long periods were I will be off the hook so to speak.