The Triton MTM Grows Legs--A MLTL Design

[Greebster]

Actually in an ML-TL both the 1/4-wavelength resonant frequency of the line's length and the port's dimensions combine to create the overall tuning frequency. The longer the line, the more it contributes to the tuning and the less from the port. Conversely the shorter the line the less it contributes and more comes from the port. In a design like this where the cabinet's internal height is the line's length, the 1/4-wave resonant frequency will fall in the range of 80-90 Hz, so an appreciable amount of the system tuning comes from the port. It's incorrect to assume, then, that the port is tuned to the driver's Fs. You could call it "just" a tall, vented box but there's another advantage that isn't usually taken into account with typical vented box modeling software, optimizing the port's location for the best combination of tuning frequency and location relative to the midwoofer(s), resulting in the smoothest overall response. The line's design center is the midpoint between the two midwoofers which is the center of the tweeter. You can use the stuffing density and location for tweaking to taste but in my experience I've never changed either after building exactly what I modeled (YMMV).
Paul

Paul, do you mean like this?...
http://www.diyaudio.com/forums/multi-way/240194-mtmmm-build.html#post3591895

Albiet not the best driver, but everything is in order wouldn't you think?

I do understand the form and function and the balance between them all. What I do find interesting is taking well known systems and modeling them in TL if I have the driver parameters. Tends to shake the ground you previously thought was stable. Port placement is very critical as is nulling the second harmonic. The example given was off by a tad as it was tuned at 47 instead of 45, ehh close enough to give a good example.

Now I have gone down the route of extending a driver response way farther than the normal alignment. I did this to confirm what could be reached with such changes, but always nulling the 2nd when doing so. Port length always changed, but always a high aspect ratio like 4" dia 4-5"long or 3"dia 3.5-4.5"long or a shallow slot port. This left a very shallow low cutoff dropping down roughly 10dB at the bottom end ~23Hz. The length, position, dampening and port length all influenced one another. The idea was this could be placed against a wall flat adding room gain to correct for the falling response.
Modeled up worked quit well using the room and placement to sum together with the speaker to yield a flat response. Not bad for a 6.5" midbass with ±6mm Xmax. Level was brought up 6 dB by using 4. System wide 8 drivers total. Powered in Active pairs. Hard cut at 23, well it is excursion limited

Mike