View Full Version : T-line CAD plans - Dual 8" subwoofer

09-10-2009, 01:30 PM
This is my first t-line build and its insane getting to grips with all the parameters!
The line is tuned to 30hz, and the chamber is 0.6 cubes. the line goes from 2" wide to 5" wide as shown:


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 until i can afford some RE8s which look good for this purpose.

Any advice on this build would be great!


09-10-2009, 01:34 PM
what subs? that chamber seems about right, could cut it down a little, but after displacement it shouldn't be too bad

idk about the expansion, it shouldn't be bad, is there any way you could start out bigger?

09-10-2009, 01:39 PM
the subs that will be going in there first are unbranded, all i know is that theyre 200Wrms, dual 4ohm. The suspention is quite tight but they have huge air-pushing power. i have 4 of them, 2 currently in a 1.3cuft L ported @ 30hz and the other two ready for the t-line.
when i get the money for the re8s though it should be better, Fs of 22hz and good Q values.

09-10-2009, 03:13 PM
Are you in Kent WA?? Anyway, the design looks great however never seen a "tapered" length of vent from 2" to 5" what's the purpose behind it?

09-10-2009, 03:13 PM
How long is the line?

09-10-2009, 03:27 PM
nah kent UK. lol. the line is about 112" long, to give the 30hz tuning. the 2 - 5" width is to make it a folded horn design - higher output (supposedly)

09-11-2009, 08:00 AM
A 112" line with an expansion ratio of 2.5 tunes it closer to 35hz, not 30hz. With that expansion, you need about 133" to give a 30hz tuning.

09-11-2009, 12:16 PM
oh right - i just did a simple freq-to-wavelength conversion for 30hz, and divided it by 4 to get 1/4 wavelength and it came out as 112.something".

09-12-2009, 12:45 AM
oh right - i just did a simple freq-to-wavelength conversion for 30hz, and divided it by 4 to get 1/4 wavelength and it came out as 112.something".

That works only when the line has a consistent area. If it tapers, it's less and if it expands, it's more. Also, don't forget to add the extra length of the compression chamber to the line length as it most certainly counts.

09-12-2009, 04:46 AM
thankyou, yeah that would make sense! im hoping that when i measure that out, the chamber and expantion of the like cancel each other out enough to give near 30hz. will the expantion realy give me increased output or am i better sticking with the same width throughout?
thanks for all your help!

09-12-2009, 07:36 AM
I changed the width of the start of the line to 3" instead of 2", which also had the effect of reducing the chamber to 0.4cuft, which may be an improvement:


I was also considering making the end of the line 4" instead of 5". This should reduce the effect of raising the tuning of the line and making the chamber smaller should let more pressure occur.

Original plan or this one better?


09-12-2009, 07:42 AM
Well, modeling this with a pair of DD1008's (I don't have the RE 8's on file, DD's should be pretty close) if you remove the compression chamber completely (you'll need to invert mount the subs) and increase the mouth size to about 2x driver SD (about 12'' wide on your plan) you'll get a more suitable response for in car use and considerably higher efficiency, 10db higher than sealed from 30-80hz.

[edit] refering to you original plan.

09-20-2009, 12:08 PM
may I hookin in this topic.?
by reading the comments on this topic
I came up with my own design (starting with 1.9" en ending with 11.8"
horn over a length of 102 inch
netto hight will be maxx 7.85inch for 2 DD1508's
outside dimensions 34.25x20.00inch


would this work? or does it need some adjustments?

09-20-2009, 12:20 PM
This was the TL I built for 2 Sundown Audio e8s



And then wrapping it up -

09-20-2009, 05:01 PM
The box design posted by OP doesn't really look like a T-Line. Looks more like a folded horn ported enclosure... T-Line doesn't have a "chamber" to really build or amplify any sound pressure, it's just the sub (or subs) firing directly into a length tuned port. Also, You really don't need to flare a T-Line. For the most part, it should stay the same width the whole length of which should be equal to the sub (or subs) combined Sd.