Transmission line speakers!

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. 

This is a great post. I learned so much about this and similar designs today that provide direction of my next speaker upgrade. Thanks for bringing TL design to the forum and thanks to all those that contributed to the discussion.

My current speaker set uses a loose concept of the TL design but I was unaware of how the construction is classified and incorrectly thought I had stumbled across a unique design. I am enamored with this low frequency sound and today have found the path to take when upgrading. Thanks again!

Irving M (Bud) Fried of IMF and Fried became a good friend of mine, and I was one of the owners of Fried Products.  He graciously gifted me his own personal loudspeakers shortly before his passing.  Bud famously championed the transmission line loading.  No one came close to evangelizing the advantages of the alignment.

What few realize is as terrific as TL is in the bass, it's even better in the midrange, as the notes simply fly out of the speakers.

Recently finished a new pair of TL subwoofers for myself to replace Bud's.  Their lovely cosmetics fit right into my living room, play cleanly and powerfully into the teens, and cost me so little most in this day and age dismiss them immediately out of hand.  More than that, the quality of the low frequencies they produce leaves me happy like few, if any I've encountered when it comes to musicality.  They simply sound more like real music, and astonish people with their sound and modest dimensions.