Transmission line speakers

Von Schweikert and Fried are two that immediately spring to mind.

Less well knoiwn are VSonics and Clements.

Less well known is VSonics and (was)Clements.

They aren't a TL? (http://www.vonschweikert.com/vrline/VR-10M.HTM) And the Frieds are a tapered, folded transmission line, which is almost identical to the design I've been using for woofers since 1980:(http://www.friedproducts.com/monitor7.html) I suppose some peoples' definitions may vary, but transmission lines CAN take various forms(even variously damped, aperiodic chambers; as long as the 1/4 wavelegth goal remains): (http://www.quarter-wave.com/TLs/TL_Anatomy.pdf)

And especially when properly used with planars, as they are innately faster than most other alignments.

Mcgarick- The term you're looking for is, "PACE"(a quality of live music that T/Ls and TQWPs retain better than most designs): (http://www.hificritic.com/downloads/Archive_A7.pdf)

When I owned my speaker company in Florida, a customer(very affluent) came in(1980) that wanted a pair of subs to go with his Acoustat Model IIIs. We experimented for some time with a number of designs and drivers(his $$). The best combo turned out to be the 10" woofer that Milo Nestorovic was using in his passive/active bass system, in an 8', tapered, folded, progressively damped(we settled on bonded dacron) transmission line. These were actively bi-amped with a Dahlquist DQ-LP1 and a Hafler DH-500(both modded). Proper damping(it took some doing) in the line effectively cancelled any frequencies but the very lowest(desired reinforcement) and eliminated them from the vent's output(no mid-bass dip). These were positioned upright(48" tall) between the planars, to eliminate time/phase problems. They integrated beautifully(no lag/great imaging and sound stage). The bi-amped KEF LS3-5A/B139 (in acoustic suspension) system I built/owned got sold, and his system duplicated, after I heard the dynamics. The only problems I've ever had with thinness have been room related(only lately). An expensive divorce forced me into a pitifully small listening room(nulls at 60/120/240hz). A modded TacT RCS 2.2X has solved that, enabling me to position the TLs, on their sides with the drivers in the room corners, to more evenly load the room(bi-amped with Maggies). No problems ever with "one note bass"(can't tell the kick from the double bass, etc/no definition or pitch). Part of that does come from having an amp that will control the driver in a basically undamped(no air suspension) enclosure too. I'm now using a modded TransNova 9505, that keeps an iron grip on the 10's. Things have progressed nicely since 1980. The only bass system I've encountered that makes me want is the Lyngdorf W-210, but I couldn't use them in my room anyway. No one sells the drivers separately now, or I'd have a pair in my TLs.

Mcgarick- Did you happen to read the article on Pace, Rhythm and Dynamics that I posted? It really brings many bass integration/presentation issues into perspective nicely. Many bass sytems will provide deep bass, but without any definition, speed or timing/phase accuracy

Ther are room correction systems available(ie: TacT, Lyngdorf), that can help you with room interaction(time/phase/freq response) problems. BUT- As long as you are enjoying the sound/music with which you are presented; nothing else matters. Happy listening!!

I sold the Acoustats some years back, when I no longer had a listening room big enough to let that system breathe(everything sounded best with 3' feet behind, 10' between, 4' open to either side of the panels, and nothing behind my seat for 15'). The TLs were tuned to have usable output down to 16hz(more visceral than audible). I used to listen to a lot of pipe organ music, on vinyl(love direct-to-disc), with the turntable in a separate, attached room to avoid feedback. Those were the days! I'm now using a pair of modded Maggies(excellent speakers), and mass quantities of Auralex. Of course- It'd be a gas to have all my present equipment and cabling(nothing's the same but the TLs) in my old listening room, and be able to swap the Acoustats in for a comparison.

Sanders had written some excellent/in depth articles on TLs and electrostatics that appeared in Speaker Builder mag, back in 1980(or so). Those were what led me to experiment with them and the(afore mentioned customer's) Acoustats.