Hi all. This is just an idea, never built them.
Use it freely and modify it if you want. Measures are in milimiters. The lenght of the line is nearly 150 cm (not sure if optimum. Optimum line lenght is driver dependent, I
suppose). Need to be stuffed maybe (trial and error I suppose if no modelling nor measuring capabilities are available, as is my case).
Drivers? Maybe Seas, Scanspeak, etc. (Fostex?)
I'm planning to send this idea to www.t-linespeakers.org which is great site if you are interested in TL's.