The Triune TL
An All Dayton MTM Transmission Line
Frequency response plot
Click on drawings for a larger image
Horizontal off-axis response curves
Impedance plot
Vertical off-axis response curves
Transmission Line: The material medium or structure that
forms all or part of a path from one place to another for
directing the transmission of energy, such as electric
currents, magnetic fields, acoustic waves, or
electromagnetic waves.

I'd considered making the "big brother" to the Triune CC using
the Dayton
295-301 5.25" shielded mid/woofer and the 275-075
Shielded silk dome.a vented design, and certainly one could
easily modify the TL design to do so. Simply reduce the
enclosure depth to accommodate the reduced volume
requirements and port out the back near the bottom. -I will leave
the details up to you. Likewise a ML TQWT could be done as
well, albeit at the expense of a larger cab. However for its
characteristic nearly linear impedance, uncolored sound, bass
extension, and simplicity of construction, I chose the classic
tapered transmission line. Parts and materials for a pair of
these should cost less than $150.00.

I've always found transmission lines intriguing, both because of
their attributes, and because for so long their design was
cloaked in mystery and conjecture, rules of thumb, and
sometimes outright bunk. The recent works of Augspurger and
Martin King, among others have removed the veil on proper
design, or at least made it somewhat more transparent…

The Design Process:
One objective of this design was to keep the enclosure volume
as small and compact as possible. Another was to utilize the
same crossover as utilized in the CC version. This is to keep the
voicing between them as close as possible. This necessitated
keeping the enclosure width narrow, and the same driver
spacing on the baffle. (Well at least on three sides.)  The TL
width is 7.5" with a 3/8" roundover on all sides. Height was
arbitrarily limited to 36 inches in keeping with the diminutive
nature of the Triune CC.

I used Martin King's
Classic Transmission Line Enclosure
Alignment Tables to design the enclosure, and verified it using
his MathCad computer models. As a sanity check I modeled the
Seas millennium drivers utilized in the Thor and essentially
replicated the same line length and volume as Joe D'Appolito's
design. While the actual line length is 48", I estimate the
effective line length to be closer to 56".
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