Sony SS-TL5

USA only - I have no idea if these were in-house Sony US developments or, more probably, the result of a collaboration with a local loudspeaker manufacturer. It is said that these were fine-tuned for "american listening preferences"...

The SS-TL series is based on the transmission line system : a column of air is pushed through an acoustic labyrinth. Said labyrinth and the front port are tuned by size, length and filling to provide the roll-off characteristic. The results are extended (but linear) bass response and improved phase response.

The SS-TL5 is a four-way system with a full front-to-back labyrinth shown below ; the SS-TL3 is a 3-way with a front-to-front tuned transmission line like that of the TL5 but no bass driver at the back. The SS-TL1 is a much smaller 2-way with a non-tuned, small, transmission line.
Only the SS-TL5 has a titanium tweeter and... real oak veneer !

The series was later augmented with an SS-TL4 (an updated SS-TL3) and perhaps other models but all are very rare at any rate.