The most noticeable feature of the transmission line speakers that I build is that I do not like to use acoustically transparent foam to fill the mouth of the line. To me it is unacceptable in a professionally built product. Instead I prefer to build a mitred aluminium frame inside the aperture and cover it with grille cloth to match the grille covering the speakers. This is a somewhat fiddly process but well worth the effort.
Another feature which cannot be seen concerns the crossover. It is generally accepted that hard wired crossovers are superior to those built on a printed circuit board. The usual way of constructing the crossover is to glue the components to the back of the connection panel. This is perfectly acceptable in a home built product but some years ago I experienced a “rattle” in one of my own speakers caused by one of the crossover components becoming loose. Since I had built them myself it was not a problem for me to fix but I would not want a repetition in any of my customer’s speakers. I now glue everything to a paxolin board and also use cable ties and plenty of solder tags to ensure security of all the components.
The next build will have the option of concealed magnetic fixings for the grille surround if desired.