# t line sub box 1/4 wave for xfl 1222



## 111brandon111 (Nov 13, 2012)

I need a little bit of help theirs no info about t lines really the best info I've gotten was off of a smd forum speed travels at 1130ft/sec so i divided 1130 by 32 Hz which equals about 35.32 then you dived 35.2 by 4 to get 1/4 wave you end up with 8.83ft. Is the 8.83ft the cubic feet or length of the box. Also to find the port area since i have a 12 (11 inch cone) dived 11/2 which equals 5.5 so then you do 5.5x5.5x3.14= est 95in of port area. My question is is the box cubic feet 8.83 or is that just the length. The subwoofer is a American bass xfl 1222 (fo Hz 31.9) (qms 3.826) (qes 0.465) (qts 0.415) please help its my first time building a t line.


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## Whiskeyface (May 27, 2012)

111brandon111 said:


> I need a little bit of help theirs no info about t lines really the best info I've gotten was off of a smd forum speed travels at 1130ft/sec so i divided 1130 by 32 Hz which equals about 35.32 then you dived 35.2 by 4 to get 1/4 wave you end up with 8.83ft. Is the 8.83ft the cubic feet or length of the box. Also to find the port area since i have a 12 (11 inch cone) dived 11/2 which equals 5.5 so then you do 5.5x5.5x3.14= est 95in of port area. My question is is the box cubic feet 8.83 or is that just the length. The subwoofer is a American bass xfl 1222 (fo Hz 31.9) (qms 3.826) (qes 0.465) (qts 0.415) please help its my first time building a t line.


 length.



Ive heard theres a sh*tload more to Tlines then just that. *theyre more like horns, but not, but wait. . . math? wtf mate* 

BUT, I havnt gotten to build one with a sub worth a darn for myself VS a sealed VS a ported VS a horn VS 4th & 6th order bandpasses so I might not be the best one to say if you should or shouldnt build one. 

I will say this though, a Tline for a 32 hz 12incher is gonna be a big box. . . im sure you could do a lot more with the 5-6ish (minimum after folds) cu ft that pigs gonna take up. . . 18s fit in 5 cuft boxes. and you can tune them to 33 hz


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## Justin Zazzi (May 28, 2012)

There are some crazy maths involved with these and very very few resources available to simulate them. I've had great success with Martin J King's website and the resources he posts there. Quarter Wavelength Loudspeaker Design

The quarter wavelength does refer to the length of the port behind the speaker. If you add polyfill or something similar to the entire port length and consistently, you can shorten the port by roughly 10-20% to save space but you will loose a little bit of overall output. This is generally not a problem because the t-line design is very efficient to begin with.

The cross-sectional area can have many different geometries, but a 3:1 ratio narrowing taper usually works well. The limit is the smaller end of the taper must be large enough to prevent any kind of breathing sound as air is pushed in and out. I and a few others I spoke with have had success with a port cross-sectional area of 2.1 (200 square inches in your case) near the woofer and gradually taper down to an area of 0.7 (67 in.^2) at the terminus.

The overall volume of the box does not matter, so long as you satisfy the above requirements for cross-sectional area and length, which will generally give you a large box. It will be more efficient and play lower notes than most any other enclosure though, but at the cost of taking up more space.


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## captainscarlett (Mar 15, 2011)

T-lines .. that's all i build! well 99.9% of the time. Hands up I've only got 6 months and over 20 builds behind me, but here goes. 

Although that SMF is good, you need the best basic read up on t-lines is 

*transmission line design fundamental* paper. if you Google it you might want to look at the 'talkaudio' result .. hint, hint! however that doesn't have any images in it.. but you'll get the idea. There is a PDF file version somewhere ... 

Personally, I don't look at the volume of the enclosure. IMHO, what make a t-line is 

1) Line length 

2) Size of line terminus - 'port size' although with t-line .. its called a line terminus not port

3) Taper angle / wave guide if designing a t-line with a taper

4) SD of the line - if building a straight t-line .... again not quite in the same consideration as calculating box volume... 

So for example, if your box is 10 wide ... and you want to make it 12" wide .. in a traditional ported enclosure that would extend the enclosure volume which has to be accounted for. With a t-line, if you did this, the main factors would still be the main factors. 

There is a new t-line software

Leonard Audio - Coming Soon

Some of what I've been doing over the last 6 months 

On the right hand side by the car was my first t-line build for over 22 years. It house a pair of Phoenix Gold 6.5" component speakers. 











My Mad Focal 6 x 9 box ... well you gotta try these things 






















hybrid audio i6sw build






















Boot build for a Ford Focus - 6.5" deep enclosure for 12" Kenwood sub





















For JBL GTO-804 8" sub - recycled MDF





























My first attempt with the Hybrid i6sw






























































































There are a few more, but like i said, i've only been 'building' for about 6 months. 

Multiple bends might lengthen the line .. producing deeper bass, but i feel the it looses a degree of efficiency (to the ear). I lean towards tapered t-lines for depth .. music, straight t-lines for output .. but again that's a generalisation. the line terminus has a huge influence on the output. 

i've produced t-lines for the 8" JBL that'll shake my car, and long t-lines with a narrow/small line terminus, that produced very musical deep bass, but no output regardless of where i have the volume, which is really nice when you want some SQ.


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