Transmission line speakers!

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

Bingo.

@roxy54  thanks, i lifted it from Wiki. i should have been more clear about that. Best to you !

Jim

My mains speakers are some transmission line IMF RSPM mark IV. 

I bought them in great condition from a junk shop a year or so ago.

My magnepan .7's and Dalhquist dqm9 have been pushed into a corner ever since. 

The IMF's are huge and heavy but are so easy on the ear. 

I am sure that design difficulty, cost of manufacture and shipping, and shear size are the reasons speaker like this became rarities.

I’m still using a pair of KEF Transmission Lines that my late father and I built in the mid ’70s.

They are made of 1’’ ply and are a CJ Rogers design with a KEF B139 bass, KEF B110 mid, KEF T27 tweeter and an ITT-STC 4001G Super tweeter.

They sound really nice with any amp but could probably do with a crossover rebuild. And a refinish as the original glued laminate hasn’t aged well and has been removed.

I have tried to include a picture but it won’t stick for some reason.

I just got a pair of Alta Audio Alec’s - my first pair of speakers with a transmission line.  Have had them for about a month, they sound fantastic.  Bass performance far exceeds anything I’ve experienced in my set up.  Very organic and non fatiguing.