Transmission line speakers

I spent the better part of a decade building various DIY transmission lines (in SpeakerBuilder magazine issue #4 of 1986 you'll find one of my designs), and in my experience there's a tradeoff: Sufficient output from the end of the line to reinforce the deep bass also results in a cancellation notch in the upper bass at the frequency where the line's effecive length is equal to 1 wavelength (which puts the line's output 180 degrees out-of-phase with the direct sound).

You can see that notch in SoundStage's measurement of a transmission line speaker:

http://www.soundstagemagazine.com/measurements/pmc_gb1/

Fortunately notches are relatively inaudible, so it looks much worse on paper than it sounds. Most people won't even know it's there.

There are techniques for minimizing this notch, but they involve tradeoffs in other areas.

That being said, a good transmission line can be a magnificent-sounding loudspeaker system, especially in the midrange as Trelja notes.

Duke

dealer/manufacturer

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

Well,what brought this all about,was a friend of mine picked up some B&W DM2a's and sold them to me for $21.00
That's what he payed for them at a thrift store here in Seattle area.
These are a transmission line speaker, and are seriously built,they would rate a 5 on an Audiogon scale as the tops are beat a little and they're old! The woofers say 1975 dated.

The bass has no boom at all,and as pointed out the mids and high are clear,very clear. There seems to be a righness to the timing of them.The sound come at you like real time,hard for my to say it right...
They are also very dynamic in nature, I love them and want to seek out others like them,or better. They stomp all the speakers I have ever had.

I wish I could post photos of them like Audiokarma,you can see them there(under the same name).



Thanks for the suggestions,I will research them all.

If anyone know more to look into, I'm all ears.

Wow the PMC's look great! I wonder what they go for used..
I must look into this.. thanks!

PCMs have gotten some very good reviews in the English press.