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Transmission Line Bass

As a long time proponent of good bass without subs, I like tinkering with different ways of approching the age old problem of recreating all energy below 100Hz.
Seriously, if you look at loudspeaker responses, everything seems goes to hell just below that point, swinging wildly in output response, almost independent of many of the typical factors that would be indicators of performance.
So, the question.
Who among us has had extensive Transmission Line Bass Experience in listening, (like me with the IMF's in days gone by, with Bud Fried being a wonderful mentor to me).
In Jim Thiel's lab, one time he told me 'candidly' that Transmission Line Designs 'in theory' don't work. (Another discussion for another time). But he, like me was a bass freak of the first order, loving a rich full bottom end, hence some of his equalized designs early on. They were an all out attempt to bend the laws of physics.
So, what do we think of Transmission Line bass--so, if you're familiar with the sonics though actual listening, and can express first hand opinions let us hear your impressions of the differences between ported, passive radiators and transmission.

Thanks in advance...

Larry
lrsky
sounds_real_audio
1,019 posts
 
I think that the most important improvement in the bass when using a Transmission Line is not so much the depth of the bass but the quality.. I attribute that to the face that the rear waves off the back of the driver is not just absorbed by the MDF (in most speakers) but rather has an outlet. This must reduce the resonance considerably. I remember when I built the Fried's using Bud's 12" driver I asked him if it would be better to use MDF the the plywood in his plans, (they were do it yourself) speakers. He told me that he didn't feel any resonance in his cabinets that were made from plywood.

Of course I ignored him, who wouldn't, he was just an old man, and I was young and much smarter then he was... then the wisdom of his choice came to light when I had to carry the speakers up stairs from my shop in the basement.

Larry lets us know how your experiment goes.

Jim
Sounds Real Audio
ngjockey
1,042 posts
 
Can you spot the problem with transmission lines...?

http://www.rwgiangiulio.com/math/pipelength.htm

The advantage is managing the phase from the back wave to reinforce or null at specific frequencies.

Traditionally, a transmission line is tapered and "stuffed" which absorbs some energy, lowers Q, and reduces bass extension. Been playing around with another idea that takes advantage of the difference between slow air movement and fast sound travel but, as yet, untested. Expect complications.
rja's avatar
rja
2,377 posts
 
Any reports on the Salk Veracity HT1-TL or HT2-TL?
I believe TL designates "transmission line" models.
face
516 posts
 
PMC is an excellent example of a well designed TL.
soundcomponents
49 posts
 
there is a really good white paper on the wisdom audio site. They are using "regenerative" transmission lines in all of their woofers - and they are the best, most musical subs I've heard.
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