Transmission line speakers!

                                       Everything tomic601 said, +1

     Below: a reprint of the article*, mentioned by MC, (01-06-2022 8:36 PM) written by Roger Sanders, who has since gained a certain amount of respect as a speaker designer.

     When I had my shoppe in Winter Park, FL (circa 1980): a customer wanted a pair of subs, to accompany his Acoustat Model III system.

     They worked so well, when loaded with the 10" drivers Speakerlab used in their Nestorovic bass system, crossed with a Dahlquist DQ-LP1 and driven by a Halfer DH-500; I built another pair for myself (and: bought a pair of Model IIIs).

     Then, built a few others, which I combined with passive crossovers, JVC ribbon tweeters, Audax dome midranges and very smooth, 10" Peerless woofers. Everything but the 10" woofers and their 5 Ways, were contained in moveable housings (for time-alignment and directivity), which sat atop the TL cabinets.

                           They sold as fast as I could build them.

     I’m still using my original pair, crossed/aligned with a TacT 2.2X, into a Hafler 9505 and: now sporting a pair of SEAS Extreme (not from Taiwan) L26ROYs.

     Their performance (measured and auditory): excellent, with a tube-driven pair of small, Emerald Physics speakers, crossed at 80Hz (10th order).

     Still have the old Nestorovic 10s, in a closet. (sentimental value, or: backup?)

           Whether just for the valuable insights/info, or: to build one’s own pair:

* http://sanderssoundsystems.com/downloads/speaker_builder_dec_1980_an_electrostatic_speaker_system_Part%20III.pdf

           More, from Roger Sanders and Speaker Builder/Audio Amateur, here:

                    http://sanderssoundsystems.com/audio-related-articles

                                                Happy listening!

One of the coolest transmission lines was the 1929 Stromberg Carlson Radio using a hand made coaxial driver (using a leather surround).  

I'll never forget the first time I heard TDL Reference speakers. I was simply blown away. For a kid still years away from a degree I couldn't even dream of laying out the dough. Eventually I did own a couple pair of TDL transmission line. A studio 1A, Studio 0.5. Should have never gotten rid of them. They were not the easiest to drive, mid 80's efficiency i recall. Needed some decent power to really make them sing. But what a sweet sounding and natural speaker they were. Beautiful, across the frequency range, amazing low end from such a small box. I still have a pair of TDL compact monitors (non transmission line design). Still a wonderful monitor using the same drivers as the bigger brothers.

TDL's are rare, and rarely mentioned here in forum, or for sale. If you spy one for sale grab it!

I'm always on the lookout. 

   All PMC speakers use transmission line designs.  Consequently, they seem to produce more and better bass than comparably sized speakers using other designs. 
   I really like my PMC Fb1i Signature speakers.  The only real knock on them I’ve ever heard is complaints about the cost, but apparently it’s not that easy to design and build good transmission line speakers.  I haven’t encountered any small 2-way towers that are better, certainly not in every parameter.  After a certain point, everything in engineering is a trade-off.