Transmission line speakers!

@roxy54: Are you thinking of the FMI (Fulton Musical Industries) Model J loudspeaker? It was comprised of three separate boxes: on the bottom a transmisionline-loaded woofer enclosure, in the middle a small sealed enclosure with an 8" woofer and dome tweeter (marketed separately as the Model 80), and on top an RTR ESL tweeter array (6 ESL tweeters per side iirc)---the same tweeter Dave Wilson used in his original WAMM loudspeaker. I bought a pair of the Model J in 1974, when it was priced at $1200/pr. JGH loved it, putting the Model J at the top of his recommended component list.

Before ESS introduced the Heil AMT loudspeaker, their flagship model was the TranStatic I, which was also a three way: a KEF B139 woofer in a transmissionline enclosure, a KEF B110 5" cone midrange, and three of the RTR ESL tweeters mentioned above. It retailed in the early-70’s for $599/each, and was competition for the Infinity Servo-Static I. I have a pair sitting in my spare room.

bdp24,

Hi, I might be giving it the wrong letter, but it was definitely Fried. They were the first mini monitors I had ever seen, and they were really mini! A small two way, amd an rectangular subwoofer that was fairly large. I saw it demoed at House of Hi Fi in Trenton NJ around 1976, when I was considering my first pair of speakers. It sounded really good, but I was 19, and nothing was going to keep me from buying either Bozak Concert Grands (which they also carried) or Klipschorns, which their competitor Hal's Hi Fi carried. The Khorns won.

My main speakers are the Stax F-81 electrostatics. Difficult load and brutally inefficient, but with the most refined and realistic midrange that I have ever heard in a beautifully stable and realistic, but small scale soundstage presentation. Love those speakers. When I crave a larger scale presentation with a livelier rhythmic vibe and much better bass performance I rotate in a pair of Paragon Regent transmission line speakers.  

Paragon Acoustics was a relatively short lived company that produced some outstanding speakers. The 92 db efficient Regent, with its lead lined interior walls (140 lb ea.) sound like a more dynamic, fuller and more extended version of my Stax. The least “boxy” sounding box speakers that I have owned. They don’t have the beautifully refined and detailed midrange of the Stax, but are not too far off in that respect. I like tomic601’s description of TL’s in general and applicable to the Regent.

*** TL speakers roll off more slowly (less steeply) at low frequencies, and they are thought to provide better driver control than standard reflex cabinet designs,^[3] are less sensitive to positioning, and tend to create a very spacious soundstage. ***

As an aside, my Manley Reference 100W triode/200W pentode switchable amps work great with both. Should be obvious which mode I use for each speaker.

Not my pair:

https://www.hifido.co.jp/sold/11-62535-22980-00.html?LNG=E

                                       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!