What is a "transmission line" speaker?

Maybe I'm a dummy, but I don't know what differentiates a transmission line speaker from any other type of cone drive speaker. Please explain.

jphilips11-21-2002 7:26pm

unsound Details Discussions Posts This discussion Message User 7,338 posts 11-21-2002 at 09:49pm Copy Comment URL Report Comment Edit Delete A "transmission line" speaker has a labyrinth at the rear of the driver(s), usually to augment bass response.
unsound Details Discussions Posts This discussion Message User 7,338 posts 11-24-2002 at 04:37am Copy Comment URL Report Comment Edit Delete Sean, you seem to know a lot more about this than I do, and I'm not trying to challange your expertise, but it seems to me that a lot of speakers that claim to be "transmission line" also claim to be fairly efficient, e.g. Meadowlark. Any further thoughts on this?
unsound Details Discussions Posts This discussion Message User 7,338 posts 11-24-2002 at 04:42am Copy Comment URL Report Comment Edit Delete Does anyone know how "transmission lines" effect time and phase coherence? I know speakers that are ported or transmission lines that claim to be time and phase coherent abound, but I would imagine it would be more difficult than with a sealed box.