Ken this is a very time consuming subject to explain.Really? I thought that Wikipedia entry was chock full of errors, misunderstandings and bizarre explanations.
Other than that, it was great.....
-k
Ken this is a very time consuming subject to explain.
The Wikipedia entry does give one a general idea about the theory of the driver loading behind this type of enclosure.
These links might be of some help to the OP.
http://www.audiokarma.org/forums/showthread.php?t=422244
http://www.audiokarma.org/forums/showthread.php?t=189662&page=2
http://www.quarter-wave.com/TLs/TL_Theory.html
To cut to the chase, it's a sort of porting method that utilizes a series of chambers inside the speaker enclosure that the air pressure created by the back wave of the bass driver has to travel through before it exits the cabinet....which when done properly embellishes bass production. This enables a small-ish bass or mid-bass driver (say 8 inches or less) to produce much more bass (higher output at lower frequencies) than it would typically be able to produce in a ported or sealed design. The end result is usually pretty impressive as you see a small bass driver but hear the type of bass production you may be accustomed to hearing from much larger bass drivers. As with all things, some designs do it better than others.
So what I getting out of it is that regardless what a transmission line is or isn't, it has a greater bass output than would be predicted by Thiele-Small theory.
As an example I have the EPI MT2, a tower design with two 4 inch woofers in a omni configuration. When tested by Stereo Review they said "The low-frequency output rolled off smoothly at about 8 dB per octave".
This is in contrast to a ported system with 24 dB/octave rolloff or an acoustic suspension with a 12 dB/octave rolloff.
Pardon my ignorance but what does "transmission Line" mean. I have a set of DCM TF600's.
:thmbsp::thmbsp::thmbsp:
I was curious about Transmission line too and the info on the net can be complicated/not to clear and kinda seem the same as a very low tuned ported box...
i found this guy explains it very well, in normal words.. lol!! check it out
https://www.youtube.com/watch?v=mq247-OCQg0
Quoting I.M. Fried [ A transmission line is defined, generally, as that system that adds mass to the diaphragm of a driver placed into it, therefore lowering the resonance of the driver below that of the driver in free air. Bass reflex and/ or air suspension systems almost invariably raise the resonance of the driver above it's free air resonance.]
Page 14-16 of the link gives the author's reflections on transmission lines.
http://www.friedproducts.com/Bud Fried/Further Reflections on Loudspeakers.pdf
If you remove the stuffing from a TL then the impedance curve below 100 Hz will look very much like a bass reflex enclosure, there will be a double humped impedance curve centered about the driver and box resonant frequencies. There will be one impedance peak below the tuning frequency and one above the tuning frequency. In both cases the resonant peak below the tuning frequency is the driver moving in and out of the cabinet and pushing air out and in from the opening (the port in the BR or the open end of the TL). The mass of air combines with the mass of the driver's moving cone and voice coil to yield a lower resonant frequency for the driver/box system. A TL has more in common with a bass reflex design then most people realize or will admit.