Transmission line speakers!

Many loudspeakers use transmission line design and you would not know it by looking at it. Many Infinity designs of the 70s were transmission line.

I'm not familiar with any transmission line speaker Infinity made.

Infinity Column and Column II, QLS-1, Quantum-2, 1001A, to name a few.

None of them were. 

Infinity made the claim, not me. Oh, I guess I did...but I was referring to the Infinity's claim. I know they aren't a true labyrinth design but they stuffed the cabinet with absorbent material and lowered the port resonance. Maybe it was just fancy sales writers but they made the claim.  

My Infinity Monitor IIa’s are transmission line.

One of my favorites, only to be replaced by my Reference Standard 2.5s which I kept for many years.

...I used to have a pair of those WTLC's...long ago, far away...

Ask me about the time we hooked up four Infinity Column IIs, and connected to a Phase Linear 700, in Pacific Stereo's big room. Even with the doors closed and way in the back of the store. They asked us to turn it down because they couldn't hear customers at the front of the store. I bought a quad for myself.   

...as opposed to absorbing resonance and allowing deeper bass from a given driver. 

Bingo.