I would be happy to get good midrange out of the TB's and
am beginning to think that the minimum for decent output is a
4 in driver like my Fostex FE127e's. I also have a set of
PVC pipes (4in diameter) with the old Radio Shack 1197's
which also perform well in a long pipe.

I did an experiment with a small baffle mount of the
TB 871-S in a PVC pipe of 41 in which is a quarterwave
length for 65 mhz IIRC.. don't quote me.

It didn't work satisfactorily in that transmission line
concept: PVC pipe with straight pipe and a hard surface
terminus at the exit in the form of a flooring tile.

Not much count.

Here is a concept that I just ran across at the Full Range Driver Forum for a Fostex. The interesting thing about this one is that
it uses a similar concept as that of the Jordan VTL but for a much
less expensive single driver. This I thought was a real 'find'
and had not seen it anywhere before.

• Fostex Spiral concept-- drawing