All I ever see is people sending links, and thats all I ever did to, was send links- to confusing brain boggler websights. Anyone with simple 8th grade- no scratch that, 6th grade level math can calculate tline enclosure dimesnions. Maybe good for a large van, but definitley not a car. Over the years I have learned tricks, and short cuts to tlines. I stick with tlines, because personally, its the Perfect box, for your sub. Its in the environment that subwoofer is built for, with absolutley NO amplifier strain, yet huge db outputs. I still have never pwersonally ran over 500watts to a tline, yet I always stay in the low 140db-high 130s with awesome SQ. Another Main plus side to tlines are, there is no back presure to keep efficiency up, xmax up, and allows the subwoofer to stop on a dime, and start back up faster than sealed, or ported designs. So, heres the formula, its simple, you would just need a pen , paper, and calculator. Quarter wave is all based on speed of sound, and length of the sound wave. But, when building a t-line for a sub based on Fs, you need to keep in mind the speakers Qts, and Qms, they should be low for SQ, Qts of. Qts is speakers total quality in Ratio to its electrical, and mechanical characteristics, Qms is the Mechanical ratio. But it cant be mixed frequecies, like a deck with a 60hz boost, and a amp with 40hz boost, you need to cancel 1 freq out, or level the 2 freq's there will be cancelation, and the sub will sound like its being pushed to hard-boost for tline have to be close to the quarter wave of the box as possible This allows you to use a shorter tline length, in comparison to the speakers natural Fs quarter wave length. But Tlines, with Low Q woofers, like. So, your looking at about 20hz almost as loud as the subs 40hz peak tunning. Lets go over the math, because thats where people get stumped the most.... This box in the tutorial I made sunday, I kind of dont want to give away to much, the rest you guys need to learn first hand. And the camera ran out of batteries, and the sun was going down, I REALLY wanted to finish it before night fall. So SOME pics, towards the end are missing. So, math--- Box is tuned to about 41hz. Notice all the 45s, even seperateing the 2 woofers, that is to keep the air flowing Cleanly, so no turbulance effects sound, or spl, and again, Reinforces the box for strength. I even filled larger gaps with Bondo, and painted the inside with blue paint, to keep the box from absorbing to much moisture- I will resin it soon-where I can. So, I started off with the wood cutting. I got all my basic cuts, then copied all the OD cuts with a router, so I dont screw up sealing joints later. Edited June 6, 2010 by Forevrbumpn I know that first post was very long winded, but its necessary. The first step is design. I need to get a 150sq inch port, 7. I just had to do something on t-line, and explain quarter wave boxes a little more, the websites that explain stuff, get confusing as hell. This was a straight fwd explanation. But with this damn s-10 blazer, there is no room for the fun stuff, I need somethin better.